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-   -   Will the 14x or 3x lens give a shallower DOF then the stock HD 20x? (https://www.dvinfo.net/forum/canon-xl-h-series-hdv-camcorders/58244-will-14x-3x-lens-give-shallower-dof-then-stock-hd-20x.html)

Shannon Rawls January 13th, 2006 10:28 PM

Will the 14x or 3x lens give a shallower DOF then the stock HD 20x?
 
I'm don't like renting the Mini35's and zeiss lenses & I don't want to buy one. I don't want to use an adapter that requires me to put it on top of the stock lens (reminiscent of my dvx/mini35 days) especially when I own a camera where the lens comes off.

So, the question is will the 14x or 3x lens give a shallower DOF then the stock HD 20x?

If not....What about getting one of those $250 PL adapters and mounting a lens directly to the camera. Yes yes, I know it multiples.....but even with the multiplication.....do you know of a lens I can put on there that will still be shallower DOF and be acceptable even with the multiplacation factor involved?

- ShannonRawls.com

Barry Green January 14th, 2006 01:22 AM

Neither the 14x nor the 3x would give you shallower DOF; it's the longer telephoto of the 20x that does that for you.

Unless... unless one of them allows super-close focus; that could get you hyper-shallow DOF, but in a real-world shooting circumstance you would never do that, certainly not with a person's face, because getting that close would result in some extreme perspective exaggeration (massive nose, etc.)

The DOF issue is tied to the lens focal length; longer lenses can give the appearance of shallower DOF (assuming you can keep the aperture open). So some PL lenses would probably be able to give you quite a bit shallower DOF; picture a 135mm prime lens at f/1.6 (is there such a thing?) That would be substantially shallower DOF than the 20x lens at 110mm and f/3.5; you'd get both longer telephoto and a more-open iris, both of which lead to shallower DOF. But -- you'd have to be so far away that it would be, for most purposes, kind of silly.

The rules for shallow DOF are pretty straightforward: open the iris as much as you can, zoom in the lens as much as you can, get as close to the subject as you can, and get the subject as far away from the background as you can.

Optional lenses help other cameras in that they let you get longer focal lengths; but with the XLH1 you have a very long 110mm already, so I don't know that you're going to find your answer looking to alternative lenses... the mini35 changes everything, of course, but if you're sticking to the 1/3" chip size, there's only so many focal lengths that make sense...

Steve Rosen January 14th, 2006 11:50 AM

There is another sollution for creating a shallow focus look that works well if you're shooting in a (very) structured invironment. Try a split diopter. It forces you to put the in-focus subject on one side, or top/bottom, of the frame, but it can create a very interesting look. Even in 35mm shooting they are occasionally used to seperate forground from background (mostly in commercials). Split diopters are expensive, but are available for rental at some places.

Jon Bickford January 14th, 2006 02:16 PM

actually the 16x manual DOES give you a considerably shallower depth of field because it is a 1.6 at full telephoto instead of a 3.5, the difference between a 3.5 and a 1.6 is quite substantial. you just have to sledgehammer a hole in the wall of your location so that you can get the camera far enough away from your subject to run it at full telephoto.

-Jon

Les Dit January 14th, 2006 03:35 PM

For shooting a given distance from the subject, there are no lenses that will change the DOF at all. The DOF is determined by the image size on the sensor combined with the FL, that's all.
If you intercept the aerial image with a ground glass ( ala Mini35 ) then you can come up with a different DOF.

Just some optics info for Y'all.
-Les

A. J. deLange January 14th, 2006 03:46 PM

DOF does not depend much on focal length. If, for example, you take a picture of an object 1m from a 35 mm lens at f/8 and can accept a circle of confusion of .027 mm the depth of field will be 0.18m. If you switch to a 28 mm lens you will have to move in to 0.8 m to get the same size image and the depth of field will be, again, 0.18m. If you select a 300 mm lens you'll have to move out to 8.6 m to get the same size image and again the depth of field will be 0.18 m.

Now if you cut your imaging area size down by a factor of 10 (35 mm film is about 36 mm wide; the CCD's in the XL cameras are about 3 mm wide) you'll need a 3.5 mm focal length to get an image which fills the same fraction of the frame at 1 m as before. As you've decreased the size of the sensor by a factor of 10 you'd better cut your allowable circle of confusion by the same amount to .0027). Under these circumstances the depth of field is about 3.5 meters for most focal lengths. In other words, DOF is a strong function of the size of the sensor. In this example changing it by a factor of 10 increased DOF by a factor of 20.

So moving back and zooming isn't going to decrease the depth of field though it often gives the appearance of doing so because things well behind the subject which are well out of focus appear right behing the subject due to the perspective flattening inherent in long focal length shots.

Robert Mann Z. January 14th, 2006 04:37 PM

if you can try out soft screen, a great way to cheat out a shallow dof from a 1/3 inch camcorder without the viewers even knowing...

http://www.indietoolbox.com/

Barry Green January 14th, 2006 05:12 PM

Quote:

Originally Posted by A. J. deLange
So moving back and zooming isn't going to decrease the depth of field though it often gives the appearance of doing so because things well behind the subject which are well out of focus appear right behing the subject due to the perspective flattening inherent in long focal length shots.

That's why I said the "appearance" of shallower DOF. I've used this example many times to show that there's definitely a very different look directly attributable to focal length. Same subject, same aperture; one shot was backed up and zoomed in, other shot was wide-angle and got close:
http://www.icexpo.com/dvx100/DOF-Combined.jpg

Jon Bickford January 14th, 2006 05:51 PM

f-stops have a bigger effect than focal lengths on depth of field and shannon clearly stated that he did not want to use a 35mm adapter, and i can't blame him, it's great on a sunny day in the park or to talk about on the internet but for any type of interiors you are going to be really hurting for light if you want to use lighting that can be powered by a typical location's native juice.

35mm adapters sound like a great idea but when you really shoot with them they're more of a pain in the a** than they should be, i think Nick said his crew figured they were running around 60asa with a pst adapter! ever try shooting interiors with 60asa film on 35mm lenses? you had better hope that your focus puller is a miracle man if there's any movement at all.

or you could rent a generator, a few 2k's and perhaps a 6k, get permission from your neighbors to let you run the generator in front of their house, get the required rental insurance which makes everything a pain... hire a couple of electrics to hump cable all over the place and now your stealthy low budget production has succeeded in attracting every cop in a 10 mile radius and plenty of lookey lous and you've spent enough on rental insurance, permits and labor that you could have rented a CineAlta and lit with 1k's plugged into wall sockets!

35mm adapters are a nice tool for certain situations but are not right for all productions.

if you fail to understand the effects that focal length and f-stops have on depth of field (which is why 35mm adapters are used, it's not the size of the chip it's the length of the lens, the bigger chip however allows you to be much closer at say, 100mm) the 20x at full wide is approximately equivalent to a 38mm lens for 35mm but the 20x is only 5.4mm long at full wide, so of course the 38mm lens will have a much shallower depth of field!

the 20x at full telephoto is 108mm @ f3.5

the 16x is 86.4mm @ f1.6

both lenses are 5.4mm 1.6 at the short end

1.6 is 5x faster than 3.5 and the manual lens is only about 20% shorter than the 20x so what you lose in focal length with the 16x you MORE than make up for with the f1.6 giving you the ability to achieve a significantly shallower depth of field as well as allowing you to use weaker lights and a lower gain setting. in still photography for example, a photo that requires 1/500th of a second @ f1.6 to get a proper exposure will require 1/100th of a second @ 3.5

one other factor to consider is that the further away the subject is from the lens the deeper the depth of field on them, eventually rolling off into infinity, so with a 100mm lens for 35mm might be able to shoot a nice head and shoulders close up from say, 12 feet away, to get that same frame with 100mm on an XL you have to be quite far away indeed, therefore rendering your depth of field around the subject much deeper.

still don't get it? rent a 16x, put it on the camera at full telephoto wide open, do the same with the 20x and you tell me what happens!

and to answer the question about the 3x lens, it will have a considerably DEEPER depth of field because obviously it is an extremely short focal length of 3.4mm

-jon

Jonas Nystrom January 15th, 2006 03:15 AM

Question
 
Jon, are you talking about 16x MANUAL or 16x OIS? Is there any difference in the specs?

Jon Bickford January 16th, 2006 07:23 PM

16x manual

Shannon Rawls January 16th, 2006 11:05 PM

you guys went scientist on me.

All I wanna know is if i pop a 16x on my XL-H1, will I get a blurry background easier then I would with my 20x, if I am say....10 feet from my actor?

Keep it simple guys....no tech talk. *smile*

- ShannonRawls.com

Matthew Greene January 16th, 2006 11:59 PM

The short answer is no, they'll be the same.

The more you zoom in and the more you open the iris the blurrier the BG. If you setup the same exact shot (framing, iris, zoom) with any of the standard lenses you'll get the same results.

A. J. deLange January 17th, 2006 07:06 AM

Short answer: For a given image size DOF depends little on focal length and a great deal on aperture. f/8 at 10 mm will give the same DOF with the 20x, 16x and 3x lenses. f/8 at 80 mm will give the same DOF with the 16x as with the 20x and it will be very close to the DOF obtained at f/8 with 10 mm if the subject fills the frame to the same degree though the images will certainly be different (much flatter with 80 mm) which may give the appearance of decreased DOF because things behind (and in front of) the subject appear to be closer to it than they do with a shorter focal length.

Richard Alvarez January 17th, 2006 09:00 AM

Just to gum up the works, the 16x is a tad faster at the long end, no? So you might could squeeze out the APPEARANCE of a bit shallower dof?


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