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Noah B
22-Aug-2013, 14:12
Hey all, I recently got a sweet Sinar F and can't seem to find any info on how to use the DOF scale for the fine focusing. I went to the Sinar website but the instructions are for the new model which has an arrow you line up. I have "F" model and not the F1,+, or 2 and on the DOF scale there are two columns, one for 4x5 and 6x9. Neither of them have an arrow like the newer one to line up, only the largest aperture (f/5.6). I'm wondering when I set the first focus point do I line up to f/5.6 then do the second focus?

Leonard Evens
22-Aug-2013, 14:49
Hey all, I recently got a sweet Sinar F and can't seem to find any info on how to use the DOF scale for the fine focusing. I went to the Sinar website but the instructions are for the new model which has an arrow you line up. I have "F" model and not the F1,+, or 2 and on the DOF scale there are two columns, one for 4x5 and 6x9. Neither of them have an arrow like the newer one to line up, only the largest aperture (f/5.6). I'm wondering when I set the first focus point do I line up to f/5.6 then do the second focus?

Depth of field is a bit more complicated than that. You should go elsewhere on the large format website and study the material there.

Let me give yo a very brief summary. Depth of field is dependent on various factors, including the format and very importantly an assumption about how sharp you need your images to be. On camera methods like the one that Sinar uses are based on assumptions that may not be appropriate for what you intend. That is why you can't just apply any calculator, on camera or not.

But let me give you a simple rule which you can use to get started. It works for 4 x 5 format assuming you focus by moving the rear standard

Focusing with the lens wide open, first focus on the nearest point you need to be in focus, and mark where on the rail the rear standard is. Then do the same thing for the most distant point you need to be in focus. Measure the distance in mm between the two marks on the rail. That is called the focus spread.

Now focus by placing the standard halfway between the near point and the far point. Multiply the focus spread (in mm) by ten and divide the result by two. That give you an approximation for the f-number you need to set the lens at.

Set the aperture to that f-number or as close to it as you can get. View the image with a loupe. Chances are you won't be able to see much of anything, particularly if your aperture is f/22 or smaller. But if what you see looks adequately in focus, then you are probably pretty close.

As I said, this is just a starting point. In practice, it is not very hard to use, but as you understand depth of field better, you will find you can do better.

Leigh
22-Aug-2013, 19:38
Depth of field is dependent on various factors, including the format...
Sorry to disagree, but the DoF on the film has absolutely nothing to do with the format.

Take a shot on an 8x10 sheet. Examine the DoF in one area in a quadrant.

Now cut that sheet in fourths, yielding four 4x5 sheets. The DoF on any of those is absolutely identical to what
was realized on the full 8x10 sheet. No difference whatsoever.

The required DoF for a given film size and magnification is a totally unrelated subject.

- Leigh

IanB
23-Aug-2013, 04:29
Sinar's instructions are here: http://www.sinar.ch/en/depth-of-field/ or here: http://di.hexagram.ca/files/manuals/cameras/sinar_introductionmanual.pdf Page 12. This should be for all cameras, including the F. You just use the scale for the format you are using - it sounds as if you understand the principle. These depth of field scales are really excellent - they set out in a practical, usable tool all the maths that Leonard above has given. (And they are format dependent.)

Could it be that the index mark has simply rubbed off? I can't see how you could use the depth of field scales without one - but it is essentially an arbitrary point, so you could probably just mark a new one.

Noah B
23-Aug-2013, 05:36
This is what my scale looks like on the F

100736

Leonard Evens
23-Aug-2013, 09:05
Sorry to disagree, but the DoF on the film has absolutely nothing to do with the format.

Take a shot on an 8x10 sheet. Examine the DoF in one area in a quadrant.

Now cut that sheet in fourths, yielding four 4x5 sheets. The DoF on any of those is absolutely identical to what
was realized on the full 8x10 sheet. No difference whatsoever.

The required DoF for a given film size and magnification is a totally unrelated subject.

- Leigh

I stand by my orginal statemnt. It is not something about which there is any serious controversy, but perhaps I should explain what I mean since there are some underlying assumptions.

The basic assumption is that one is going to enlarge the image produced in the camera to produce a print of some specific size. If you do that, then the degree of enlargement will depend on the format. So, for example, if you want to produce an 8 x 10 print, you will enlarge a 4 x 5 image by 2 X, and you will enlarge a 2 x 2 1/2 image by 4X. To produce a desired quality in the print, you will have to start with a maximum circle of confusion (coc) half the size in the latter case than in the former case. Since the depth of field you attain is dependent on the coc, it depends on the format.

Note that is it is the relation of the format of the image recorded in the camera to that of the desired print that is relevant. In your example, you cut the print into four quarters. I assume you would intend to cut the image in the camera also into four quarters. In that case, the degree of enlargement would be the same as when using the full camera image and the full print. So, assuming the prints are viewed from the same viewing point and the same resolution is desired in the relevant prints, you would have the same DOF. But this is a rather special circumstance. Usually when discussing DOF, you have some camera format and some print format. If you keep the same print format and view the print the same way with the same expectation, the DOF depends strongly on the format of the camera image. That is the more typical situation.

Leigh
23-Aug-2013, 09:12
Note that is it is the relation of the format of the image recorded in the camera to that of the desired print that is relevant.
That's correct.

But simply stating that DoF varies with film format, absent an explanation of the assumptions about
magnification factor that affect the calculations, is misleading and incomplete.

The required DoF on a final print depends on
1 - viewing distance
2 - acceptable Circle of Confusion

The DoF on the film required to achieve those goals depends on
1 - magnification factor

The standard DoF calculations use assumed values for all those parameters, which may not
be correct in a particular situation.

In particular, it embeds a very inaccurate understanding in a newbie brain of how DoF works and
how the required aperture is properly calculated.

For example, I shot newspaper sports for four years using a Graphic 4x5. The images were reduced
significantly to fit in one (occasionally two) colums. DoF was not a concern at all.

However, it would have mattered had the same negative been enlarged to 16"x20" for a wall display.

- Leigh

Noah B
23-Aug-2013, 09:46
I assume I line up the bottom of the 4x5 part to the white dot? Anybody?

Drew Wiley
23-Aug-2013, 09:50
Indeed. Depth of field calculations intended as a convenience for tabletop studio and typical publication needs don't necessarily equate to other applications. For
example, all you have to engage is some complicated landscape matter and a significant degree of enlargement, and then the rules become much more subjective,
depending on your creative intent and not just the technical parameters. Even though I often use a Sinar, I gave up on all those redundant calculations and markings long ago because they didn't have much relation to what I actually did. Other than basic zero detents on my equipment, everything else is fine-tuned visually, using the groundglass, loupe, and gut experience. Maybe if you're a scientific, food, or product studio photographer, such things can be helpful. I've even switched over
to the earlier Norma version of Sinar, which doesn't have any of those scales or yaw-free features, and the quality of focus hasn't suffered a bit. I don't even pay
attention to the levels or angle markings on the swings and tilts. I have fine-tuned the correction on all the detents and zero locks, but everything else is done
visually.

Noah B
23-Aug-2013, 11:07
Thanks Drew, I mostly photograph objects that are 1:1 or greater and I quickly found out this morning that the dof scale isn't that helpful with such high magnification. I did use the mm measurements as Leonard suggested and did some calculations and they came out alright. I was using a cambo before and relied on whatever was on the GG while stopping down and looking at the image. I figured I'd give this new way a try. Much appreciated gents!

Captain_joe6
23-Aug-2013, 13:34
Discussion aside, the Sinar system works like this:

Assuming you're working with 4x5, then what you do is 1) with your aperture set wide open, focus on the farthest point you want to be in sharp focus. 2) The DOF scale should spin around the body of the knob, so that the scale can be turned independently of the knob itself. Turn it so that the white mark on the left (in your picture of the knob) lines up with the black gap in the silver printing, below "5.6" and above "4x5". 3) Now turn the focus knob so that the nearest point you want in sharp focus, is in focus. The white mark by the knob should be lined up with a new number on the DOF scale. This is your suggested working aperture. 4) Set the aperture, then turn the focus knob forward so that the white mark is lined up with the scale TWO STOPS LESS than your original calculation. This is your final focus point. 5) meter and expose.

It sounds complicated, but in practice, goes like this:

I'm photographing a tractor set up in front of my barn, and there's a dog in front of the tractor. I want them all in sharp focus. I focus on the barn, zero the DOF scale, then focus on the dog. Looking at my DOF scale, I see that the white mark lines up with f/16. Now I turn the knob the other direction, so that the white mark lines up with f/8 on the DOF scale. I set my aperture for f/16, meter, and take my picture.

Good luck.

dionisius1976
8-May-2015, 00:47
http://di.hexagram.ca/files/manuals/cameras/sinar_introductionmanual.pdf