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Old November 19th, 2010, 10:12 AM   #1
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CMOS knife edge DOF to much ??

In the F3 forum I made a comment on the appearence of the F3's focus and others politely disagreed with me. In watching the very shallow depth of field from this CMOS I question whether the industry will provide the neccessary viewfinders, LCD's and focusing systems or is accurate focus relegated to the must have accessories? The footage in the F3 forum was excellent work and my comments I feel stepped on some toes but I have to be honest, I still feel as though extremely shallow DOF can miss critical focus and has limited use. Such as the swimming video in the F3 forum http://www.dvinfo.net/forum/sony-xdc...3-footage.html at the 10 second mark a portion of the the hat is in focus, appx 1/3. For me it isn't enough. Another piece of footage shows a glass blower and the entire picture looked OOF for a split second. The possibility exist that it was just test footage and not seen as critical or it could be that I am just wrong.
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Old November 19th, 2010, 10:26 AM   #2
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I wonder about the DOF with increased F stop, I would like to see some street scenes to see how deep it can be.
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CMOS knife edge DOF   to much  ??-hd-hat.jpg   CMOS knife edge DOF   to much  ??-glass-hd.jpg  

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Old November 19th, 2010, 10:29 AM   #3
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While shallow depth of field is a technique used to isolate and draw attention to your subject, just because you can do shallow depth of field on a camera, doesn't mean you have to. Depth of field is selectable by f stop adjustment, and whether the eyes and the ears are in focus, or only the eyes is an artistic decision. Obviously, if you close down the aperature, you gain depth of field, but you also have to decide what to do to give your scene more light. On bright days its not a problem. And in fact, if you want shallow depth of field on those days, you are limited to employment of ND filters if you want to keep your shutter at 180 degrees.

The point of the 35mm frame size camera is to give you the same relative depth of fields that cinema film shooters have been using for near a century. The lenses lengths and fstops employed by film makers can now be employed in a digital film setting, making the use of that film technique available to us. In addition, the larger sensor size, provides better light gathering capablity, making it possible to shoot in the lower and available light situations. Those two factors are all this revolution is about.
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Old November 19th, 2010, 10:34 AM   #4
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Originally Posted by Don Parrish View Post
I wonder about the DOF with increased F stop, I would like to see some street scenes to see how deep it can be.
A wide angle lens, say a 17mm, at f22 is going to exhibit deep almost unlimited depth of field. An 85mm, much much shallower, even at F22.

There are some issues with running lenses completely closed down too, so I try to keep f stops between wide open, and F11.
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Old November 19th, 2010, 10:44 AM   #5
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Does the F3 appear to hunt occaisionally to you ?? I have looked for but can't find any specs on the F3's LCD. Is there some ratio or formula to what an LCD has to be to replicate accurate focus on 1080p ?? I see the "knife edge" miss sometimes. Such as the seen where the woman is sitting streetside, it seems to hit the back of the chair rather than her face
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Old November 19th, 2010, 10:51 AM   #6
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How much DOF is a creative decision, although there's also a practical aspect of perhaps needing to shoot with a wide aperture for exposure at low light levels.

Currently there's a fashion for extremely shallow DOF, although not all productions use this, but in presenting these new cameras there's a desire to show off this effect for marketing reasons.

In making your film you've got the choice of stops, perhaps more so with these cameras (and the AF100). This is because you don't need to use the shallow DOF to cover the moire artefacts found on the DSLR cameras due to the OLPF being selected for stills rather than shooting HD video.

The down side to the shallow DOF is a higher risk of soft or out of focus shots, which may restrict people to shooting more static subjects or focusing on a particular spot within the frame. This is OK, but it can be a bit limiting in film making and story telling technique, if rather pretty. Being cynical, it risks being the zoom of our time - remembering the 1960s Angenieux lens flares.

The F3 is manually focused, so it's prone to the same focus errors as any 35mm film camera, and many focus pullers say it's even more critical on 35mm sensor digital cameras.

Best use the DOF that suits your film.
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Old November 19th, 2010, 05:16 PM   #7
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Originally Posted by Don Parrish View Post
Does the F3 appear to hunt occaisionally to you ?? I have looked for but can't find any specs on the F3's LCD. Is there some ratio or formula to what an LCD has to be to replicate accurate focus on 1080p ?? I see the "knife edge" miss sometimes. Such as the seen where the woman is sitting streetside, it seems to hit the back of the chair rather than her face
Looking at your frame grab and then going back to film, it appears to me that the focus was preset to catch the male actor as he came into frame-- it more center of the table and at his hands. I don't think there was an attempt to have her in focus in the shot, and they probably intended the shot of him in frame to last longer.
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Old November 20th, 2010, 02:34 AM   #8
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Originally Posted by Brian Drysdale View Post
How much DOF is a creative decision, although there's also a practical aspect of perhaps needing to shoot with a wide aperture for exposure at low light levels.

Currently there's a fashion for extremely shallow DOF, although not all productions use this, but in presenting these new cameras there's a desire to show off this effect for marketing reasons...
(SNIP)

The down side to the shallow DOF is a higher risk of soft or out of focus shots, which may restrict people to shooting more static subjects or focusing on a particular spot within the frame. This is OK, but it can be a bit limiting in film making and story telling technique, if rather pretty. Being cynical, it risks being the zoom of our time - remembering the 1960s Angenieux lens flares...
(SNIP)

Best use the DOF that suits your film.
That seems to hit the nail exactly on the head. When I see Wedding footage where only part of the bride's nose is in focus, and the rest of her face (let alone any background) is just a blur I do worry sometimes.

I could use a bigger range of DOF at times, but I wouldn't like to sacrifice the ability to use the deep end of the scale occasionally.
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Old November 20th, 2010, 04:49 AM   #9
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Just thought I'd chime in on this after Colin's comment about the Bride's nose.

Yes it does appear to be the fashion to present a work with a very narrow DOF when many older practitioners have fought to use it sparingly. Have a look at Vimeo's overall winner. Great VIDEO but you have to think the opo was constantly searching for focus on many of the shots and it has become a signature of the whole shoot.

Possibly many are coming from "Film" School (as opposed to a "Video" School) with this instilled into them, and the 5D & 7D are a lot more affordable and accessible than an Arri to mimic a filmic style. How many graduates of this similar thinking want to admit to go on to shoot VIDEO - and to differentiate the genre the use of the term "videographer" has been usurped into the vocabulary and we are now stuck with it? But it's too late - the crossover has happened.

But getting back to Colin's observation, which I agree with, we are now seeing the affordable "film-maker's" kit of Canon 5D with obligatory narrow DOF plus SliderCam with the result that almost everything appears to be a predicatable expression of abstract visual nonesense getting in the way of a good story.
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Last edited by Claire Buckley; November 20th, 2010 at 04:53 AM. Reason: typo
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Old November 20th, 2010, 05:08 AM   #10
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That seems to hit the nail exactly on the head. When I see Wedding footage where only part of the bride's nose is in focus, and the rest of her face (let alone any background) is just a blur I do worry sometimes.
If you're doing this effect, the eye(s) are to be in focus, not the nose. The nose suggests there's a strange smell or we're watching "Bewitched".
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Old November 20th, 2010, 07:35 AM   #11
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with the result that almost everything appears to be a predicatable expression of abstract visual nonesense getting in the way of a good story.
Excellent expression Claire !! I wish i could express myself with a pen the way you do .

Perhaps the DSLR video craze has created wall, a place where photographers stumble ? An image should evoke a feeling and footage should tell a story (theres always exceptions). Should the entire Brides face be in focus ? Is the answer that simple, what do you want me to see? If there is a label on the hat, let me see the entire label, is there something on the brides nose? if not, let me see the entire bride.

Some latitude should be given to the F3 videographers as the story was showing off the F3, some critique to be given that some footage should have given us a wider variety of shots, DOF and scenes the camera is capable of. But maybe a stern lesson to ourselves about what "focus" really means, where it should be, what we are trying to convey and whether we are pleasing ourselves or an audience.

As an image what does this grab say, as footage does it miss ??
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