f32 for portraits?

[brent79]

Hello,
I will be photographing some tight faces on 4x5 using a Fujinon-W 180mm 5.6. I'm using a ring light and want to get the catchlight in the eye as large as possible.
I did a test at f22 and noticed a real razor sharp shallow DOF (maybe its just my focus is off?). All I want is the nose, eyes, and until before the ear starts in focus. And I couldnt achieve this with f22.
I am considering stopping down to f32 but am wondering if diffraction will start to play a factor in losing sharpness? I intend to make quite large prints out of this. Unfortunately where Im at now its impossible to make more tests.
Any advice would be great and thanks in advance!
B

[Brian Stein]

DOF is related to aperture, focal length, acceptable sharpness (quantified as the circle of confusion which is bigger the bigger the filmsize) and distance to subject.

For your case you have a biggish piece of film, you have a smallish aperture so despite your longish lens your DOF would be fine at greater distance.....the tight in bit is what is giving you the tiny DOF.

For some quantitation look at eg http://www.dofmaster.com/doftable.html.

[brent79]

Thanks Brian,
I think I was more wondering how the falloff in quality would be from f22 to f32 with the Fujinon-W 180mm 5.6?

[Jack Dahlgren]

I doubt there will be any falloff in quality. You will probably get a better shot and won't notice the difference in diffraction. Diffraction is not a huge problem at f/32

[ic-racer]

I agree f/32 should be fine for your purposes. It would be like using f/11 on a 35mm camera.

[Ken Lee]

"I did a test at f22"

Can you make another test, at f/32 ? There's probably no need to make a print. Just look with a loupe, and see if you can tell the difference between the negatives at f/22 and f/32.

The difference will probably be so slight, that even if you can see it with a loupe, the rest of the process will render it negligible.

"I intend to make quite large prints out of this."

Your idea of large, may differ from others' idea. How large do you mean ?

[VictoriaPerelet]

Brent, I do not think that F32 will give you significant diffraction. What sort/brand/power level of ring flash are using?

[jb7]

How large is 'quite large'?

That will determine everything.

DOF is determined by enlargement, as well as some of the other factors mentioned above.
Plus, if you're getting very close, on 4x5, then you could be talking about an effective aperture of f/45, if you set your lens to f/32.
(I know, I got it wrong on another forum recently ...)

DOF and diffraction limitations will become more apparent the larger you go-
using a smaller original at high resolution might be a better option...

It really depends on your definition of 'quite large', I think-

[mandoman7]

The difference between F:22 and F:32 will not be as significant as you might expect, either in sharpness or DOF. A change in DOF might be better handled with lens and distance changing, rather than one F stop adjustment.

Nothing like a test run. I always learn more than I thought I would when I do a dry run first.

[brent79]

Hi and thanks to everyone who responded.
I'm actually unable to make another test, in SE Asia and moving around at the moment
I'm using a profoto ring light and taking the shots about 2 to 2.5 feet from the subject.
I would like to make prints around 50 or 60 inches on the long side if possible
I cant attach the test I shot and scanned since its too large, but depth of field at f22 is very shallow, eyes sharp, forehead soft, I guess I will give it a go at f32 and cross my fingers!

[jb7]

I think you're being modest, you've gone beyond 'quite large'.

There are quite a few interlinked variables here-
so let's start with your taking distance, 2 - 2.5 ft.

I suspect that distance is going to be determined by your flash output, though I could be wrong-
however, you should factor in an extra stop of illumination for working that close-
so f/22 indicated on your flash or meter might be f/16 on the lens-
a face in close up might have a magnification of 0.5x.

That distance might seem fairly close anyway, though it depends on the picture you want-

Depth of field limitations will become more apparent at large print sizes-
it'll be much more apparent than diffraction, from all viewing distances.
Diffraction might only become apparent at closer viewing distances,
but at the apertures you mention, it will lead to an overall softening compared to working at a more optimal setting.

Diffraction won't be as immediately apparent as something being out of focus, however-
if you want zones of equal sharpness, there's no alternative to stopping down.
Though you might also find that a less than sharp nose might be acceptable, I don't know-

I think that achieving the depth of field you mentioned will drive you beyond the diffraction limits of your system-
however, as has been mentioned, there's no substitute for testing-

And even so, you could very well find the results to be acceptable anyway-

[cjbroadbent]

.... I'm using a ring light and want to get the catchlight in the eye as large as possible......
Beside the point perhaps, but that big doughnut in the eyeball won't do much for your subject. The ringlight is useful for fill - and even then requres retouching out - but as a key light it does tend to replace the pupils.

[ic-racer]

So those will be good sized :)

For me, I work the acceptable Airy disk size equation backwards. It really depends on what I find acceptable when actually viewing the print. Then I work backwards and get the number (my acceptable Airy disk size) so that I can use it on a future project.

If you are examining it close enough to see that shallow of a DOF, I'll bet you'll see a small improvement even going to f16. But when the prints are being displayed will the viewer be that close?

[Jack Dahlgren]

Hi and thanks to everyone who responded.
I'm actually unable to make another test, in SE Asia and moving around at the moment
I'm using a profoto ring light and taking the shots about 2 to 2.5 feet from the subject.
I would like to make prints around 50 or 60 inches on the long side if possible
I cant attach the test I shot and scanned since its too large, but depth of field at f22 is very shallow, eyes sharp, forehead soft, I guess I will give it a go at f32 and cross my fingers!

Since you can not test where you are - and you plan on using the negatives for some very expensive prints, I'd burn a few extra sheets of film at different apertures (f/32, f/45 etc.) to be certain. How much would it cost you to go back? It would be foolish to save a a couple bucks per sitting if you spent thousands to get where you are and are planning to make prints for hundreds if not thousands of dollars for the portfolio.