6x9 crown graphic type camera?

jose angel · Mar 26, 2015

Why would DOF be different with a bigger piece of film and the same lens from the same distance?

You don`t want to use the same lens in a smaller format.
The advantage of a smaller format is that you can use a shorter lens to get the very same field of view. And to get the same DoF you can use a wider aperture, so more light gathered by the film. (Or, simply use the same aperture to get more DoF).
Why? Because the DoF is proportional to the lens focal lenght (inversely proportional).
If you use the same lens, magnification is the same, as is the DoF, despite of the format.

John Koehrer · Mar 26, 2015

jose angel said:
Why would DOF be different with a bigger piece of film and the same lens from the same distance?

If the physical aperture(not f stop) is the same the DOF is the same regardless of distance or film size.

Limitation of shutter speed is a physical limitation because of blade size and weight to move. There were a few leaf shutters with 500th and I believe one with 1000th. Both used a second booster spring in the shutter to get there.

FWIW 1/500(leaf shutter) is usually nowhere near accurate, typically running 1/2-1 stop slow.

Dan Fromm · Mar 27, 2015

GaryFlorida said:
Are there any such cameras where you dont have to remove the ground glass to take a picture and can use different lenses up to 300mm?

With respect to your first question, you're really asking whether there are insertion type film holders for 2x3 cameras.

All sheet film holders are insertion type. There are, however, fewer emulsions offered on 2x3 sheet film than on 120 roll film.

AFAIK there are two insertion type roll holders for 2x3 press/view cameras. Busch made one for the 2x3 Busch Pressman. These beasties are very rare, accept 120 film. And there's the much despised Adapt-A-Roll 620. These can feed from a 120 spool but must take up on a 620 spool. I'm happy with mine, use them with 2x3 Graphics and a 2x3 Cambo.

GaryFlorida · Mar 27, 2015

jose angel said:
Resolution is a factor to take into account in a given print size, as is, according to your requirements, the depth of field. 20x30" is so big.

And the depth of field is related to magnification. So smaller formats have their advantages here. You may need to shoot at f45 for DoF in 6x9, while at a wider aperture for the same DoF in a smaller format. All this is photography basics.

I said a Harley because I think it is about 6-9ft lenght... a 7.5ft is certainly a big bird. You can calculate magnification with a 300mm lens, at 100ft (30 meters) it wil be 1:100... aproximately 25mm in the middle of the frame. Not a big deal.

There are not so many prints in 20x30", actually. Well, this is a "compact" size for Clide Butcher... In fact, I think there are not sheets in 30" (I know 20x24"), you probably need to go for paper in rolls. Check B&H for prices.

Let me ask you this. Are you saying that for a given focal length (say 300mm), a lens designed for 4 x 5 will have less DOF than 2 x 3 or 35mm? and is that why I would need a tiny aperture to get the depth of field I need?

Jim Jones · Mar 27, 2015

Depth of field is a more complex subject than many realize. It depends on what is being photographed, the size and viewing distance of the finished image, focal length, aperture, and personal preferences. If you want to do some serious reading on the subject, search for articles by Harold Merklinger such as http://www.trenholm.org/hmmerk/HMArtls.html.

MattKing · Mar 27, 2015

GaryFlorida said:
Let me ask you this. Are you saying that for a given focal length (say 300mm), a lens designed for 4 x 5 will have less DOF than 2 x 3 or 35mm? and is that why I would need a tiny aperture to get the depth of field I need?

You have tied yourself into a knot over this, because you are paying too much attention to the focal length of the lens.

If you fill a small negative with your subject using the lens of a focal length appropriate for that negative, using a set aperture, then you will observe more depth of field than if you fill a large negative with your subject using the lens of a focal length appropriate for that negative, using the same aperture.

If you use lenses of the same focal length on each format, the depth of field will be the same on the two films, however you will need to crop the larger negative to fill your print with the same subject. Both the uncropped negative and the cropped negative will require the same enlargement to fill the print. Most likely, however, the lens used for the smaller format will give higher quality on that small format than the lens used for the larger format will give on the small, cropped portion of it's normal format.

jose angel · Mar 28, 2015

Jim has provided the link to Merklinger`s writings, which are the source many large format shooters have used to know about this topic. Norman Koren also have a good one.

As mentioned, the depth of field is related to the aperture diameter (entrance pupil). This aperture is given by the focal lenght and the f number. (Diameter=FL/f number). So the depth of field increases as the focal lenght decreases (keeping the f number), or as the f number increases (stop down).

If you use a 300mm at f45 on a 4x5", a 6x9 and a 35mm (full format), you`ll get the very same DoF, because the diameter of the entrance pupil doesn`t vary. As mentioned, the format size is irrelevant.

But you need to take into account the print to make your calculations. The larger the print the more detail you need on the film. The DoF you get on the film must be in accordance to the print size and viewing distance.

If you are using a 300mm in all cases, you`ll get a slight advantage using a larger format, because the level of detail needed on a given print size (circle of confusion) is not as high as with a smaller format. The DoF will be slightly larger then.

The DoF is a fuzzy concept, more "mathematical" than "realistic", many people use internet DoF charts like if it were the panacea. We use to think on a few aspects of the shot, but as mentioned, it is only a part of the final image... the print. They are intimately related. The "simple resolution" is not that simple at all.

But (I understand) the point here is what to do if you cannot find a 300mm lens for your 6x9 camera, or what to do if you get the 300 but you need to get a wider aperture (while keeping a reasonable DoF), in order to use a faster shutter speed to freeze the action. You may also need to keep the same field of view (the bird should pass into the viewfinder area!): Use a smaller format with a shorter lens.

(And the format issue; again, IMHO larger is not always better. Sometimes is better (easier, cheaper, faster, sharper, and the most important, feasible) to shoot smaller than to shoot slightly bit larger with no reason).

6x9 crown graphic type camera?

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