Hi Michael,

<< I have read the article in DVinfo which clearly states that zooming in will not affect DoF as it cancels out the net effect. >>

Actually that's not what it says... it really reads like this: "If you zoom in without moving the camera back, then DoF will decrease."

In other words, the DV Creators tutorial is sort of correct, but the problem with that technique is -- as Jeff states in his article on our site -- that you're now changing the relative size of the object you're shooting... which is going to look weird unless you're shooting the entire production this way (otherwise the resultant change in object size is really going to stand out).

Hope this helps,

Thanks to Chris Hurd bailing me out of my computer illiteracy, I can post this photo. It's a still from a video clip I shot on my XL-1s. I shot it in manual exposure (F2.8, or 3.6, I forget which), manual focus, frame mode using a 1/2 black promist filter. Great, afternoon low-angle light helped get this look.

http://www.dvinfo.net/media/Image0.jpg

Indeed, the picture (from the Canon site) portrays what Jason is trying to achieve, but sorry guys, that picture just does not cut it. A high shutter setting is being used, probably at least 1,000 of a second or higher. This will result in a narrower depth of field than a normal shutter setting of 1/60, but will also result in motion jerkiness that is simply not acceptable for normal shooting situations. It also requires a tremendous amount of light to achieve, way beyond the usual interior lighting set-up. And again, the background is a considerable distance from subjects and camera. Actually, the effect in this picture could have been heightened even more by using a longer focal length. As long as the people in frame don't move, the high shutter speed will not be objectionable. High speed shutter has been used quite effectively in movies such as "Saving Private Ryan" and "Gladiator" to add a "special look to" scenes of battle.

Michael, regardless of what format you shoot with, be it 35mm motion picture film, 16mm, 2/3" chips or 1/3" chips, depth of field is a result of focal length and aperature (iris). The basic rule is: the longer the focal length and/or the wider the aperature (lower numbers, eg f/1.6), the narrower the depth of field. The shorter the focal length and/or the narrower the aperature (higher numbers, eg f/16), the greater the depth of field. This is true for all formats, bearing in mind that larger image surfaces, such as 35mm will yield narrower depth of field, and smaller image surfaces will yield much greater depth of field, but the predeeding rule still applys. This is physics and cannot be ignored. So the narrowest depth of field any given format is capable of, will be found using the widest aperature at the longest focal length. This can be confirmed using the Panavision depth of field guide I mentioned above. (Be wary: zoom lenses seldom perform optimally at their longest focal length at widest aperature)

Charles lovely picture is an example of long focal length and wide aperature equals narrow depth of field. But what it teaches budding filmmakers is never shoot an actor with a head bigger than a duck.

Wayne... "the picture (from the Canon site)" -- I'm trying to get away from it being known as a Canon site; it's actually an "everything site" now, with some Sony stuff up there too, and JVC and Panasonic material forthcoming. If you have anything that's non-Canon that you'd like to contribute, I'd warmly welcome it!

Any other DoF image examples, anybody?

<<<-- Originally posted by Chris Hurd : Wayne... "the picture (from the Canon site)" -- I'm trying to get away from it being known as a Canon site; it's actually an "everything site" now, with some Sony stuff up there too, and JVC and Panasonic material forthcoming. -->>>

I think there is some confusion Chris. I was referring to the link in James Emory's post, www.canondv.com. If that isn't the Canon website, I must be having an halucination. Which would not be all that unusual.

Wayne:

It's a goose. Goosies go: "honk, honk."

Duckies go: "Aflac."

Wayne -- thanks for the clarification, looks like the confusion was all mine, hallucenogenics aside.... that's what I get for not following the thread as closely as I should.

Just to reinforce just how "deep" DOF on a 1/3" camera can be...

I was recently making some test shots in which I was trying to shoot a close subject while keeping a local landmark, visible through a window, in identifiable focus. I tried a wide variety of exposure and subject lighting combinations, 22 all told. In the end, the landmark remained easily identifiable and only a few shots markedly blurred it. The landmark was over 1 (straight-line) mile away.

Perhaps the best way to envision the effect of aperture on DOF is to try the poor-man's glasses trick, particularly if you're near-sighted. Curl your index finger until there's only a tiny opening. Then peer through it and adjust the opening until you can see some object clearly. As you widen the opening the object blurs. That's basically what's happening in the camera with respect to the iris.

I dont wish to be argumentative but I would like to dispel the notion that DOF has anything to do with CCD size - it does not

The Three Factors which affect DOF are

1 Focal Length
2 Aperture - f-stop
3 Camera to Subject distance

CCD size will introduce telephoto compression effects which enter play for smaller CCDs

http://www.8mm.filmshooting.com/community/articles/dof.php

has an article which should be read since it is an extract from Ilford Manual of Photography, 4th Edition, 1949. Pages 14 to 17

Also for shallow DOF effect you should be aware that Circle of Confusion extends one third in front of subject focal plane and two thirds behind subject focal plane

so using this for the background blur effect you need - arrange your camera to subject distance to be approx 1/4 (or less) of the distance of the camera to the background. Then the aperture will act as a background blur control (small f number - more blur)

hope this helps

John

http://www.8mm.filmshooting.com/

Fascinating site -- thanks for the link,

<<<-- Originally posted by Jeff Donald : It depends on how important the object size is. In their examples, notice how the size of the persons head increases in size. If you can work with your subject size being larger, then changing the focal length will decrease DOF. If the subject size must remain the same size (News Anchors head size) then zooming in (decreasing DOF) will be offset by changing distance to subject. The key is if the subject must remain the same size or not.

DV Creators is correct in a limited way. They do not explain the consequences of changing subject size and the Law of Reciprocity. They are repeating the same misconceptions most people have with DOF. -->>>


So , from what I understand, is this. To achieve a shallow DoF, we either zoom in, or we put the camcorder closer to the subject. Both will have the same result as long as the object size remain constant rite?

Which also means, the bigger the object size, the shallower the DoF since both method, zooming in and putting the camcorder closer will increase the object size, rite?

I don't think you are being argumentative John, but I do think you are in error, or perhaps making a semantic argument that went way over my head.

In regards to chip size and depth of field, may I offer the following from tvtechnology.com:


The Elusive Film Look by Randy Hoffner 4/7/03

http://www.tvtechnology.com/features/Tech-Corner/f_rf_technology_corner.shtml


"You might recall that the depth of field is the range of object distances from the camera lens over which everything appears to be in focus. As lens aperture or f number decreases, depth of field increases, and, if the f number is held constant, as the size of the image decreases, depth of field also increases. The result is that for the same f number, a 2/3-inch CCD camera will have about 2.2 times the depth of field that a 35mm camera will have. As many 35mm movie lenses are designed to function optimally at maximum aperture, which may be as much as f/1.6, there is no chance that a 2/3-inch video camera will achieve the same depth of field as a movie camera. So while it is technically possible to use a 35mm movie lens with a 2/3-inch video camera, the angle of view and depth of field will not mimic 35mm film at all. One solution is to mount the 35mm lens so that its image is generated on a ground-glass screen outside the camera (increasing the image size to that of a 35mm film frame), and using relay optics to route the image to the CCD sensors. This would increase the size, complexity and price of the video camera system."


If a 2/3inch video camera has 2.2 times the depth of field of a 35mm camera, how much greater is the depth of field of a 1/3 or 1/4 inch camera?

Additionally I disagree with your contention that distance to subject affects depth of field. Only in so far as you may use a longer focal length for subjects that are farther away, as in the case of Charles' duck, er, goose. Only focal length and aperture affect dof.

In comparing the chart from the super 8 site with the Panavision guide, I find them quite compatible. (Using the 1/4 inch video on the Panavision) No conflict here.

This is an interesting discussion, but I am afraid it only serves to add to the confusion for the newbies, who are probably figuring, "Hey, if these guys can't agree, there must be some way to get blurred backgrounds for my movie with my GL1 (or whatever)." But unfortunately there is not, unless you want to shoot your entire movie outside at the longest focal length you have with a wide open aperture.

Wayne: This is an interesting discussion, but I am afraid it only serves to add to the confusion for the newbies, who are probably figuring, "Hey, if these guys can't agree, there must be some way to get blurred backgrounds for my movie with my GL1 (or whatever)." But unfortunately there is not, unless you want to shoot your entire movie outside at the longest focal length you have with a wide open aperture.Indeed. Well I think there is one statement we can all agree on: getting shallow DOF with video cameras, even big ones, is hard without making practical and/or compositional compromises.

And sometimes you have to step in goose poop.

The formula for determining DOF must have distance from camera to subject. The Panavision site requires it, as well as any other DOF chart or scale. The formula from my article (http://www.dvinfo.net/conf/showthread.php?s=&threadid=3926) is directly from the eighth edition of the American Cinematographers Manual, pages 698 and 699. Without the distance from camera to subject you can only determine hyperfocal distance (which is required for DOF). Let's not reinvent physics here, it's required, end of subject.

DOF does not always extend 1/3 in front and 2/3 behind the subject. It varies with the hyperfocal distance and many times is 1/2 and 1/2.

There are five factors that effect DOF and not three. They are stated in my article.

CCD size or target size effects DOF as stated in my article. If your subject must stay a certain size (News anchors head on TV) then CCD (or negative size) will effect DOF. Why? Because you must change one of the variables to keep target size the same. When you change one of the variables, you change DOF, end of subject.

If you have questions, read the article. If there is something you don't understand, post back. All questions are welcome.

I have a huge page to print out now. THis weekend i'll give it a go with the new GL2. I'll get back to you all with what works and what doesn't. Thank-you all for the insight ( no pun intended ). I love this forum. Everyone is so into filming here!

Chat soon

I don't quite know how to respond to Jeff's last post, as he seems to be getting a bit tite about all this. I have visited his tutorial, and while there is nothing there to rabidly disagree with, I feel that it is way more information than is necessary to resolve the dilemma of depth of field. For instance, Circle of Confusion is a rather arcane subject that is not often brought up when calculating depth of field on the set. CoC varies with different lenses of similar focal lengths, from different manufacturers. It really is not going to affect depth of field calculations of a fixed lens on a mini dv camcorder.

Frame rate will also affect dof, but that is hardly an issue for video cameras, except the DVX100, and once you set it, it becomes a constant.

Filtration will affect depth of field, if you use an ND. But this is not mentioned in most discussions of dof, because what you are really doing is changing the aperture.

Distance to subject must be known to calculate dof, but then it is constant. If you move to a different distance to the subject, you must re-calculate the dof.

1) The longer the focal length, the narrower the depth of field. The wider the focal length, the greater the depth of field.
2)The wider the aperture setting, the narrower the depth of field. The narrower the aperture setting, the greater the depth of field.

Here are a few pictures to illustrate these points: (Charles Newcomb, this duck's for you)

http://www.digitalprods.com/Ducks.jpg

Here are some publicity comments on the unveiling of the Arricam:
"Camera assistants will become “system’s managers” as they master the Lens Data System (LDS) that “shows relevant information from the lens in use, such as focus and iris settings, the focal length, as well as the resulting depth of field, all on a convenient display.”

Note that "relevant information" is; focus (distance to subject) plus iris setting plus focal length equal depth of field. No need for a long discussion, or, as Jeff likes to put it, "end of subject."

Please go to the following link for more excellent information on depth of field:
http://octopus.drama.bris.ac.uk/OnlineDocs/FocusPulling/

Finally, in no way is my intention to denigrate the hard work Jeff Donald has put in on his tutorial on depth of field, but I do feel that for the person who may be new to this concept, and is trying to apply it in a practical situation, that maybe he has gone a bit overboard with the information.

In the Army, they say there are two kinds of information; Need to know, and nice to know. It is my humble opinion that in the discussion of depth of field, items 1) and 2) above are "need to know" and all else is "nice to know."

Here are some publicity comments on the unveiling of the Arricam:
"Camera assistants will become ?system?s managers? as they master the Lens Data System (LDS) that ?shows relevant information from the lens in use, such as focus and iris settings, the focal length, as well as the resulting depth of field, all on a convenient display.?

Note that "relevant information" is; focus (distance to subject) plus iris setting plus focal length equal depth of field. No need for a long discussion, or, as Jeff likes to put it, "end of subject."

Do you have a link to the article, I'd like to read it? I suspect it does not show Coc because it would be fixed data and would not change, why clutter the display with information that would not change.

Circle of Confusion
The diameter of a circle formed by a lens imaging a true point. The largest circle which the eye will perceive as a point, without producing perceptible unsharpness (lack of focus). Is the primary factor in determining image sharpness to the viewer.

As the aperture is stopped down, the Coc is reduced in diameter. However, spherical aberration causes the plane of sharpest focus to shift or move along the optical axis, toward the CCD.

The smallest area of intersection for crossing light rays produces not a point, but a circle. This is the origin of the term Circle of Confusion. If the circle has a diameter of 1/3000 of the viewing distance, or less, it is perceived by the eye to be a point (therefore sharp and in focus). As the viewing distance increases, physically larger diameter circles are perceived by the eye to still be a point.

The diameter of the Coc is not a fixed number, nor is it's size agreed upon as an industry standard. The 1/3000 figure is the most commonly accepted. It translates to a size of .01 inches or .25mm. For many applications 1/300 of an inch is the standard. The bottom line is sharpness, or the lack there of, is in the eye of the beholder. What appears sharp to me may not appear sharp to you, or vice versa.

Why do I dwell on accuracy in discussing things of a technical nature? Well, to put it quite simply, I teach photography. Each term I have students take my classes that want to reinvent DOF or Coc. They have their own limited knowledge and personal experience with trying to deal with it and learn it. There are several threads here where members have tried to invent the formula for DOF from their experimentation around the kitchen table. It doesn't work that way. We need to have agreed upon standards and definitions so that an intelligent discussion can take place.

What happens if people only have the information they "need to know." Well, in science they make false and/or inaccurate assumptions. Complete and accurate information is required for intelligent discussion. I don't think the army wants to encourage too much intelligent discussion.

But this information might be too hard for me? I doubt it. I've had students from 18 to 80 take my classes and have no problem understanding DOF or Coc. The biggest problem is many of my students have "learned" misinformation or inaccurate information about DOF. They've been to web sites, read articles, talked to so-called experts and been misinformed or received half truths. I feel it is our responsibility to see that does not occur at DV Info.

<<<-- Originally posted by Jeff Donald : Do you have a link to the article, I'd like to read it? I suspect it does not show Coc because it would be fixed data and would not change, why clutter the display with information that would not change. -->>>

http://www.cameraguild.com/interviews/chat_alsobrook/alsobrook_machines5.htm

Gee, Jeff, that's kind of my point. Why get into discussions about CoC when it really does not enter into determing depth of field for a camera with a built in lens? And even with a camera with interchangeable lenses, such as the Canon XL1s, how would the user determine the CoC and apply that information to his set-up? Coc is of interest when your choice is between a Cooke Prime and your Panavision Zoom, but I have a hard time seeing the value to a quarter inch chip camera, and just how does this apply to Jason's original question:

"I have been trying to get the camera to focus on people a few feet away and then blur the background.

What is the trick to this with the GL2?"

Again, my point is that narrow depth of field is impossible to achieve with small chip cameras under normal conditions, so rather than fighting it, work with it and use other methods to give separation to your background. And very often the added depth of field will work in your favor. I hear people complain that they can't get a remote focus for their DVX100 to use when the camera is mounted on a jib. Hey, when you are shooting full wide at f/4, everything from 2 feet to infinity is in focus, so what are you worrying about focus? See, every cloud has a silver tinted lining.

<<<-- Originally posted by Wayne Orr : Again, my point is that narrow depth of field is impossible to achieve with small chip cameras under normal conditions, so rather than fighting it, work with it and use other methods to give separation to your background. -->>>

I wholeheartedly disagree with this. My experience with the small camera format goes from Canon 814 & Nizo 2056 Super8, right through Video8 and Hi8 and now to DV with VX2k , 950, 900.


Follow my advice given earlier and slim DOF (blurry foreground or background ) is a cinch.

Then John, I am sure you will be happy to post a clip or two for our examination. Earlier you wrote:

"so using this for the background blur effect you need - arrange your camera to subject distance to be approx 1/4 (or less) of the distance of the camera to the background. Then the aperture will act as a background blur control (small f number - more blur)"

So, if we are shooting an actor that is ten feet from the lens, to get the blur effect the background must be an additional thirty feet away? That's handy.

Wayne

check back tomorrow and the shots are yours its a bit dark over here at the moment

Wayne,

Gee, Jeff, that's kind of my point. Why get into discussions about CoC when it really does not enter into determining depth of field for a camera with a built in lens?
I didn't bring up Coc in this discussion. It was brought up by you and Jay. I brought it up in my original thread because it is the "Ultimate DOF Skinny". I need to define DOF because it had not been defined for the members here. As one of the factors determining DOF, Coc was mentioned in that article. However, since you and Jay brought it up I felt it necessary to accurately define it for members and guests not familiar with the term.

You ask why discuss Coc when it does not enter into determining DOF? It's very simple. You can not determine DOF without having a value (size) for Coc. Every chart, scale, guide, Palm program will allow you to add a value or uses a predefined one. The Panavision site uses predetermined Coc in their equations. You can not define sharpness without Coc. Most people have a curiosity about those things. If all this is old hat, I'm sorry. Gloss over my instructions, but understand, many members and guests want to learn as much as they can (I've already received 3 emails on the subject).

Chris,
"Any other DoF image examples, anybody?"

I have a couple of DOF frames but need some advice on how to post them.

Thanks,
Bob

Jeff writes, "I didn't bring up Coc in this discussion. It was brought up by you and Jay."
Excuse me, Jeff, but the first mention of Circle of Confusion (aptly named for this discussion) was brought up by you in an earlier response to my recommendation of the Panavision site. You wrote:
"The Panavision site uses non-standard values for CoC."

A few other comments. You did not respond to my quote on the Arricam:
"...the Lens Data System (LDS) that “shows relevant information from the lens in use, such as focus and iris settings, the focal length, as well as the resulting depth of field..."

No mention of the two missing factors from your "5 factors for determining depth of field," although later you did say;
"I suspect it (the LDS) does not show Coc because it would be fixed data and would not change, why clutter the display with information that would not change."

But later you said,
"The diameter of the Coc is not a fixed number, nor is it's size agreed upon as an industry standard."
How can it be "fixed data" one moment, and then "not a fixed number, nor its size agreed upon," the next? Later, I asked, "just how does this apply to Jason's original question:" which was

"I have been trying to get the camera to focus on people a few feet away and then blur the background.

What is the trick to this with the GL2?" No reply from J.D.

You write: "You can not determine DOF without having a value (size) for Coc. Every chart, scale, guide, Palm program will allow you to add a value or uses a predefined one."

Oh? The "Kelly-Wheel" which is used by film camera assistants to determine depth of field does not list the Circle of Confusion.

One final reference:
"The depth of field in an image is controlled by three factors: the distance to the subject, the focal length, and the aperture used to capture the image."

"For users of compact digital cameras, depth of field is a subject of special interest becuase depth of field is more difficult to control with a compact digital camera than with earlier film cameras. The small imaging sensors of compact cameras require the use of short focal lengths, and this in turn gives these cameras an unusually long depth of field when compared to 35mm cameras. Thus, intentionally getting a shallow depth of field is more difficult."
http://www.megapixel.net/cgi-bin/fs_loader.pl?p=http%3A//www.megapixel.net/html/articles/article-dof.html (this is an excellent site with good graphics to explain depth of field)

For John Jay, who writes, "Follow my advice given earlier and slim DOF (blurry foreground or background ) is a cinch."

"The bad news is that it is much more difficult, using a digital camera, to blow the background out of focus, which is a pleasing effect in portrait and nature photography. You will have to use the longest possible focal length, and keep your lens wide open. Well, there is no free lunch. I'm not retiring my 35 mm SLRs yet. (2002 note: I'm lying! In the last year I went through just two rolls of film.)

In close-up photography, the greatly increased depth of field is a lifesaver. I never had so good, sharp tabletop pictures as I have now, in the digital domain."
http://www.wrotniak.net/photo/dof/
Andrzej (Un-jay) Wrotniak

Wayne Orr
Caveat Emptor

I stand corrected, I did mention Coc first, because of the Panavision use of non standard Coc values for some formats. My apologies to you and Jay.

I still stand by my assertion that many members and guests have an interest in DOF and Coc. Many are film photographers and while they can't apply all of this to video, it is very applicable to their traditional film photography and darkroom work. This is quite obvious by the number of views this thread is getting and the number of emails I'm receiving.

I've not commented on the link I asked for because it is a lengthy article and I could not easily find the quote. I can't find where Alsobrook is talking about Arricam. When I have more time I'll read the article. Sorry.

The Kelly-Wheel uses a fixed Coc, like the Panavision site.

All five factors are listed in the DOF Skinny thread and DV Info article.

The Coc value changes with the size of CCD or negative used. Once established for your size CCD the value will remain fixed. You have noted the larger format cameras have less DOF. Why? They have a different value Coc.

I thought your asking of Jason's original question was a sort of rhetorical question or something on your part. My answer to Jason's original question is contained in previous posts. Jason stated he would experiment with the suggestions and post back results and further questions. Now I'm pretty much trying to help you understand it.

I previously mentioned that a great many articles and web sites have errors and half truths. This is evidenced by your continued reference to these sites that list only 3 factors for DOF. I thought the American Cinematographers Manual, 8th edition (published by the America Society of Cinematographers) and their published formula would be good enough for you. Their formula requires five values.
1. focal length of the lens
2. f-stop number (size)
3. Coc
4. distance from camera to object (subject)
5. Hyperfocal distance (derived from first 3 values)

In the article and Ultimate thread I list the fifth value as "The viewer's personal standard of the permissible degree of sharpness (or unsharpness)". This is after all a subjective medium. I don't argue sharpness. If you insist your image is in focus, who am I to argue with you.

I'm sure that would get me a lot of work. Yeah.

Jeff, you and I are never going to walk down the aisle. I think you are obfuscating a subject that to people using camcorders should not be so complicated, based on my considerable experience. It would be totally out of the realm of reality to expect someone with a GL1 shooting a "movie" to sit down and "do the math" in the formula for depth of field you refer to, everytime they set up a shot.

It also does not answer the original question, "how do I blur the background?"

Wayne Orr
Caveat canem

<<<-- Originally posted by Wayne Orr : Again, my point is that narrow depth of field is impossible to achieve with small chip cameras under normal conditions, so rather than fighting it, work with it and use other methods to give separation to your background. -->>>


Wayne,

you asked for some frames....

Technical Data

f1.6
shutter 425
subject distance 1.6m
background distance 6.3m
Optical zoom 50% approx 22mm
Axe : Sony TRV950E
Ambient temperature 16 C
Weather Cloudy Dull
Frame Rate 50i

Procedure - record to DV then grab stills to Memory stick 640x480 then upload to yahoo briefcase as below

DOF examples of background blur (dofbg) and foreground blur (doffg) found here

http://photos.yahoo.com/bc/agentpurpletwo/vwp?.dir=/dof&.src=ph&.dnm=dofbg.jpg&.view=t&.done=http%3a//photos.yahoo.com/bc/agentpurpletwo/lst%3f%26.dir=/dof%26.src=ph%26.view=t

http://photos.yahoo.com/bc/agentpurpletwo/vwp?.dir=/dof&.src=ph&.dnm=doffg.jpg&.view=t&.done=http%3a//photos.yahoo.com/bc/agentpurpletwo/lst%3f%26.dir=/dof%26.src=ph%26.view=t

John, I hardly know what to say. I guess then, your advice to someone looking for the blurry background would be:
Shoot wide open, at 22mm, at shutter speed of 425 (never mind the jerky motion), make sure your background is at least 20 away, and your subject is the size of a liter of Coke, and you will end up with a somewhat blurry background. Perfect.

May I recommend to you the movie, "The Patriot," starring Mel Gibson. I think you will find some of the blurry background pictures in that film are more in keeping with what Jason had in mind. And no motion effects from the hi speed shutter used in your pix.

Sorry, John, no sale.

Wayne Orr
Veni, vidi, vici

The way I do it is like this... it's very technical, so try to stay with me.

Okay. I point the camera at the subject and fuss around with the lens and exposure settings. If I get it to work, cool. If I can't, I blame it on poor lighting or Canon... sometimes both.

<<<-- Originally posted by Wayne Orr : Again, my point is that narrow depth of field is impossible to achieve with small chip cameras under normal conditions, so rather than fighting it, work with it and use other methods to give separation to your background. -->>>

Wayne,

I objected to your statement above and have provided two real world examples.

Members are reminded to review our FAQ (http://www.dvinfo.net/conf/misc.php?s=&action=faq#cool) regarding disagreements with other members.

Folks -- please note: In a few of these preceding posts, I've had to edit out a few comments that were somewhat nasty... please proceed with this debate, but do so on an elevated level like the mature adults we all are. I would like to think that we can disagree with each other but still buy each other the round of beer. This place is for friendly discussions and debates, or at least it will have that *appearance* but I would rather not have to baby-sit. Let's please relax, keep the thread open, and proceed with cool heads and warm, fuzzy feelings for each other... or else! Much respect,

Wayne, I'm not sure what your trying to sayShoot wide open, at 22mm,
An inch is a little more than 22mm. John says the distance is 1.6mm or a little over 5 feet. A little close, but reasonable for an interview. The subject size is fine for product shots and similar type work that I do. For an interview the subject size is too large and would require either less zoom or increase the camera to subject distance (either will reduce subject size and increase DOF).

Other than for Ken's last post, I get the feeling you guys are leading Jason to believe that there is actually something he can do to create a narrow depth of field with a quarter inch chip camera, and that simply is not going to happen in a real world situation. (I am not talking about shooting extreme close-ups of the head of a coin)

John has used a Sony TRV950e and it uses 1/4.7 inch (.21 inch) chips. The DOF is about 19% greater with John's camera than the 1/4 inch chips in Jason's GL2. By using the Panavision Calculator for the 1/4 inch chips we see the DOF for Jason's camera is about 6 inches front to rear. Using the same information and changing the CCD size to 1/3 inch (XL1 and others) the DOF drops to under 3 inches. John used a real world situation that was not the head of a coin. He met your challenge. Live with it.

No one is implying or stating that 1/4 inch, 1/3 inch or even 2/3 inch CCD's will achieve the DOF of a 35mm or even a 16mm film camera. But just because you don't have the same tools, it doesn't mean that you give up. I am suggesting that people learn the whole truth about DOF and use it as best they can to their advantage.

The shutter speed argument is irrelevant. Shutter speed can be controlled through the use of ND filters. Neither John, nor his example should be criticized for his lack of owning or using ND filters to control shutter speed. Someone with considerable experience would realize that.

It would be totally out of the realm of reality to expect someone with a GL1 shooting a "movie" to sit down and "do the math" in the formula for depth of field you refer to, every time they set up a shot.
As I previously stated this type of shooting does not lend itself to run and gun or ENG style shooting. The formula is too complicated for you to use your slide rule. That's why they make Kelly-Wheels, DOF charts and Palm programs. They use the formula and the user inputs the non fixed, variable data. It takes only a few seconds to input the data. I know many camera operators that use Palms (PDA's) on the set for just such a purpose.

I think you are obfuscating a subject that to people using camcorders should not be so complicated
I'm sorry you think I am clouding the subject. Quite to the contrary, from reader mail, I would say I'm clearing up and making DOF and Coc clearer for many people. The vast majority of my students understand the principles, concepts and practical uses in less than an hour. The actual implementation of the principles is a life long pursuit and study.

Caveat canem, can you explain why I should beware the dog?

Jeff

Thx for wrangling this one!

Just a few points

The 950 was used to prove the point that even small chips can get slim DOF - useful for cutaway shots to spice up your edits

Also, I have many ND filters, but since it was a quick n dirty test it was easier to ramp the speed to fix the exposure issue.


Also heres a nice duck shot I found from J Beale site, shot with his DVX100

http://www.bealecorner.com/dvx100/frames/duck01.jpg

Also, I have many ND filters, but since it was a quick n dirty test it was easier to ramp the speed to fix the exposure issue.

I assumed as much, thanks for the clarification.

Jeff

Since you are having trouble understanding what I have to say, I will try to explain in more detail.
John said he used the "optical zoom 50%, approx 22mm. That is, his focal length was 22mm, approximately, since these cameras do not have exact focal length markings, which also makes it difficult to calculate exact depth of field. With me so far?

Extrapolating his information to my PD150, 50% focal length would be approx. 33mm. We will use the f/1.4, although in the real world, the PD150 only opens to f/1.6. Entering the same subject distance of 5.2ft (1.6m), we use the Panavision calculator (nice to see you using it, although we know it is flawed) and arrive at a depth of field of 2.82 inches. Hey, we agree. We also agree that the "field of view" this represents is way too restricted for "normal" shooting conditions. That field of view is, 9.162 inches across by 6.8 inches high, or, about the size of a "liter of Coke," as illustrated by John's picture. Doesn't leave much room for head and shoulders, does it?

Hooray. We now have narrow depth of field with a small chip camera. How did we do that? In this case, by opening up to f/1.4. Easy? No. In John's pictures he had to increase the shutter speed to 425 to eat up enough light to get to f/1.4, which is fine for still pix, but results in undesireable motion characteristics when people and cameras move. "The shutter speed argument is irrelevant. Shutter speed can be controlled through the use of ND filters." Excuse me, its not the shutter speed we are trying to control, its the aperature. John chose to control the aperture by increasing the shutter speed; what you mean to say is, control the aperture by adding ND's in front of the lens. How much additional ND? I don't know off hand. And it will vary depending on the lighting conditions. And actually I don't care because I feel that John's pictures support my contention. What?

You quoted me: "I get the feeling you guys are leading Jason to believe that there is actually something he can do to create a narrow depth of field with a quarter inch chip camera, and that simply is not going to happen in a real world situation." Yes, I said that (seems like weeks ago) and I still stand by it. In John's photos, despite using an extremely narrow angle of view (6 degrees approx), which as has been pointed out would not contain a head and shoulders shot, despite the lens being set at maximum aperture, and despite the background being at least 20 feet away, the best John was able to produce, was a modestly blurred background. Because the depth of field is so great with these cameras, the focus will soften slowly over distance. And you are telling me to "live with it"? Don't be so arrogant, Jeff, that dog might bite you in the a**.

But in the end, it's up to you people who are being entertained (and maybe enlightened just a bit) to make the final decision. You can shoot your films outdoors with long lenses and distant backgrounds, trying to get those elusive blurry backgrounds, or, you can spend your creative energies working on composition, lighting, art direction, and other techniques that will improve your images, working within the limits of the medium.

I wish you all the very best.

Wayne Orr
Dominus Vobiscum

Bob Harotunian:

"I have a couple of DOF frames but need some advice on how to post them."

Sorry for the delay in getting back to you. Just email them to me, and I'll host them for you from the web site and post the link to them.

Jeff,

If one is looking for more real estate in a Slim DOF shot, may I suggest the use of a full height anamorphic adapter. I have upped a shot to illustrate this at

http://photos.yahoo.com/bc/agentpurpletwo/vwp?.dir=/dof&.src=ph&.dnm=dofbgws.jpg&.view=t&.done=http%3a//photos.yahoo.com/bc/agentpurpletwo/lst%3f%26.dir=/dof%26.src=ph%26.view=t

The anamorphic adapter works like an optical compander and has no net effect on DOF but does have the advantage of a 33% increase in image width. Thus head and shoulder shots are possible with differential focus from the background.

If one is unhappy with the degree of blur in the background a matte can be created using an unsharp mask to allow anything to be done to the background in post.

The real issue here is that there has to be some differential focus sufficient to give a definite threshold for the unsharp mask to determine a sharpness silhouette, after which it is a matter of a few mouse clicks and some render time - this is well within the capability of small chip cams and is a far cheaper solution to renting arricam/ moviecam, a daVinci best light, stock plus processing and maybe a colourist.

Another low cost approach would be green/blue screen or a difference matte for non-moving backgrounds

OK. Now that I have everyone thinking I am against blurry backgrounds, I am going to show you some of my stills with blurry backgrounds, taken from a little project I did last year. They have attached comments.

http://www.digitalprods.com/DofF.jpg

I'll take my turn in the barrel, so feel free to take your best shot. So to speak.

Those shots look really nice Wayne!

I read this entire thread I thought okay after all of these people with way more experience say one thing or the other I just did what Jeff said originally and it worked in my house and the setup took all of 2 minutes. I used my XL1s set the app to 1.6, frame mode, shutter speed of 30. The subject was a regular size DVD movie type case roughly the size of someone’s head I shot it from about 8 1/2 feet away while the blue wheels (stroller) are about 9 feet away and it was pretty blurry while the case was in sharp focus.

Here is a link to a scene capture on my site

ftp://totalsolutions.bz/pub/FlyontheDVD.jpg

If you look closely on the top left corner of the DVD there is a fly chilling out didn't notice it tell I was about to post the picture ;-)

Nice shot... My experience is the same as yours!

PD150/170/vx2100 vs. DVX100, which one can get a shallow DOF easier (means don't need to go 3 streets away to shoot the target!) and nicer?