Diffraction. When does it really matter with LF?

[Vaughn]

Some have suggested a magnifier eyeglasses, let's say around 4x. WOuld that work. It would free up my hands as an additional benefit as I need both hands to controls the two knobs required to focus my H-1?

I recommended the glasses not for focusing, but for being able to clearly see the whole 4x5 GG in focus while under the darkcloth for the purpose of composition. One generally can not compose with a loupe. Ask you eye doctor, bring in your camera if she or he does not understand your needs.

Yes, one has to move ones head around -- the brightest view is always to put your eye on the same path as the light coming in through the lens. Fresnels help a little but you don't get something for nothing. I don't like them.

[Michael R]

Alan, even if you get over “f/22 syndrome” you will probably end up at f/22 or smaller anyway.

[Drew Wiley]

If you're on the beach with your dog, you can play fresnel frisbee. That's about all they're good for as far as I'm concerned. Having the right kind of grind on your glass to begin with is way more important.

[Doremus Scudder]

... So how do people decide the best f stops on the fly. I know there are some special LF tables you can look up. But the whole process seems too arcane and I'm having enough trouble focusing and seeing things upside down to figure out a better stop other than f/22. Anyone with simple suggestions?

No "simplistic" suggestions, nope. But, the method of choosing an optimum f-stop based on focus spread, once mastered, is really, really simple in application. It takes me about five seconds to decide which f-stop is going to work best for any particular shot. It's not arcane in the least.

I seem to keep posting this link, but here it is again, from the LF home page and the article "How to select the f-stop."

https://www.largeformatphotography.info/fstop.html

Heck, if you're lazy or just want the down-and-dirty approach, you don't even have to read the whole article. Just figure out the basic method, print out the tables listed toward the end of the article and paste them on your camera and go to work.

A couple of observations: Most LF lenses work best at or close to f/22. So, there's very little reason to shoot at a larger aperture than that unless you want a shallow depth of field and need the larger aperture for that.

However, if you want lots of near and far things in your photographs to be in focus, there is a very good reason to stop down farther than f/22 when you need the depth of field, despite the slight fall off of performance caused by the (very gradual) onset of diffraction degradation.

You have to enlarge a 4x5 negative a lot to notice diffraction degradation from f/32. How many 30x36-inch prints do you make anyway? Heck, 11x14s from negatives made at f/45 exhibit little or no degradation due to diffraction unless you get out your loupe.

So, in practice, you'll be using a small range of apertures between f/22 and f/45, depending on the focus spread. For those scenes that require stopping down a lot, you may want to keep your print size smaller than 16x20 inches.

Measuring focus spread between the nearest and farthest objects you want in sharp focus is simple. Consulting the chart to find the optimum f-stop is also simple.

You wanted a simple approach; well, there it is, staring you in the face. You just need to get past the initial inertia and read through the article. You don't have to figure your own values for circles of confusion or anything; just use the ones the author does and you'll be very well off. You can always revisit and tweak the method if you find you need to later.

Best,

Doremus

[Doremus Scudder]

Alan,

I seem to be moved to comment on viewing and focusing on the ground glass as well. Here's my take:

First, working with a view camera is different than using small or medium format cameras that have viewfinders that you hold to your eye. A common mistake, in my view, is trying to use the LF ground glass to compose the image with, like you would use the viewfinder of your smaller camera. Deciding what you should point your LF camera at should happen in large part before you drag the camera and tripod out and set everything up.

If you have a clear idea of where you want to stand (sit or whatever) and where you want the borders of the scene to be before you set up, then you don't have to spend a lot of time agonizing with the ground glass. You just have to choose a lens that gets your scene on the negative and make some little adjustments to get your movements right and your camera pointed where it needs to be so you're not cropping off any of your desired image.

If you're spending a lot of time moving your camera (and tripod) back and forth and side to side to find the right spot, you're still living in the eye-level-viewfinder world. If you need a viewfinder to help you find the right camera position, use a viewing frame (that's what I do - I rarely have to move the tripod to a better location after I've set it up initially - and when I do, it's usually due to my choosing an impossible shot from the depth-of-field considerations or not having a wide-enough lens with me).

When I work, I find my camera position by walking around and examining the scene (using my viewing frame) till I find the position that gives me the perspective I want. I'll climb up on things, do some deep knee-bends, whatever I need, to find the right place. Then, I'll set up my tripod, place the camera platform under my chin, and adjust my tripod to that height. Only then do I bother to unpack the camera.

If you work like that, you don't even need to spend much time viewing the ground glass; just enough to ensure your scene is there and check whatever focus points you need to apply movements and focus. Sometimes I don't even take time to look at the whole scene projected on the ground glass; I'll just check the edges and then grab the loupe and start focusing. If I don't need movements, I just have to check near and far focus points, position focus halfway between them, choose my f-stop and make the photograph. I don't worry about hot spots, fall-off, etc. As long as I can see the two or three things I need to focus on with my loupe and I know that my desired edges are in the picture, I don't even care if I look at the whole image. I don't check depth-of-field either; I'm confident that I can get my focus points sharp using the near-far method of choosing the f-stop.

I will check for vignetting when needed. And, sometimes I spend a lot of time working on movements to get the plane of sharp focus positioned optimally, but even then, I only need to be able to view my chosen focus points through the loupe.

Best,

Doremus

[Drew Wiley]

Heck, Doremus, I just love spending time looking at that opalescent image on a big ground glass, even if I don't even take a shot. And I'm damn nitpicky about how the frame specifically crops the composition. Moving the tripod an inch either direction might spoil it. When I see a promising spot, I generally stake it out, literally - I stab one of my walking poles into the soil at that exact spot. Then I walk around a little more, seeing if there's an even better spot. That's half the fun of it. The hunt is just as important as the kill.
Depth of field then becomes yet another compositional "hunt". And no rote formula can substitute for that "just right" feel on the ground glass itself, which is double-checked in critical spots with a loupe of course - those places in the composition I want the eye drawn into due to its acute focus, versus where I want the eye to slightly recede. Don't confuse that with gross selective focus; that's OK, but I often aim for a much more subconscious effect on the viewer. A good illusionist does not show his hand.

[Alan Klein]

Probably not. You might ask them.

What do I ask?

[Alan Klein]

Alan,

I seem to be moved to comment on viewing and focusing on the ground glass as well. Here's my take:

First, working with a view camera is different than using small or medium format cameras that have viewfinders that you hold to your eye. A common mistake, in my view, is trying to use the LF ground glass to compose the image with, like you would use the viewfinder of your smaller camera. Deciding what you should point your LF camera at should happen in large part before you drag the camera and tripod out and set everything up.

If you have a clear idea of where you want to stand (sit or whatever) and where you want the borders of the scene to be before you set up, then you don't have to spend a lot of time agonizing with the ground glass. You just have to choose a lens that gets your scene on the negative and make some little adjustments to get your movements right and your camera pointed where it needs to be so you're not cropping off any of your desired image.

If you're spending a lot of time moving your camera (and tripod) back and forth and side to side to find the right spot, you're still living in the eye-level-viewfinder world. If you need a viewfinder to help you find the right camera position, use a viewing frame (that's what I do - I rarely have to move the tripod to a better location after I've set it up initially - and when I do, it's usually due to my choosing an impossible shot from the depth-of-field considerations or not having a wide-enough lens with me).

When I work, I find my camera position by walking around and examining the scene (using my viewing frame) till I find the position that gives me the perspective I want. I'll climb up on things, do some deep knee-bends, whatever I need, to find the right place. Then, I'll set up my tripod, place the camera platform under my chin, and adjust my tripod to that height. Only then do I bother to unpack the camera.

If you work like that, you don't even need to spend much time viewing the ground glass; just enough to ensure your scene is there and check whatever focus points you need to apply movements and focus. Sometimes I don't even take time to look at the whole scene projected on the ground glass; I'll just check the edges and then grab the loupe and start focusing. If I don't need movements, I just have to check near and far focus points, position focus halfway between them, choose my f-stop and make the photograph. I don't worry about hot spots, fall-off, etc. As long as I can see the two or three things I need to focus on with my loupe and I know that my desired edges are in the picture, I don't even care if I look at the whole image. I don't check depth-of-field either; I'm confident that I can get my focus points sharp using the near-far method of choosing the f-stop.

I will check for vignetting when needed. And, sometimes I spend a lot of time working on movements to get the plane of sharp focus positioned optimally, but even then, I only need to be able to view my chosen focus points through the loupe.

Best,

Doremus

That's what I've been doing using a micro 4/3 camera as a viewfinder in BW display if shooting BW and finding the spot before I place the tripod and camera. I also have been using the camera as a meter, but that's another story.

So a few hours ago, I was out shooting with a 75mm lens. The main object was about 4' to 80-100 feet. I focused on the far point using the asymmetrical line where the axis of the standard is. Then tilted the back standard backward to focus the near log up at the tip about four feet away. I set it for f32 and fired away. I just realized though that tilts probably aren't required with a 75mm. At f/32 I was covered from around 3 feet to infinity at coc of .1mm, with the hyperfocal at 6 feet. SHould I have used that and skipped tilts?

So that raises a general question about tilts. When shooting with wide angle lenses like a 75mm, it doesn;t seem even required to worry about them. Just use the DOF tables What's the advise here? Also, the DOF chart I used uses .1mm COC. I could change that if another COC is better. Advise?

[Alan Klein]

No "simplistic" suggestions, nope. But, the method of choosing an optimum f-stop based on focus spread, once mastered, is really, really simple in application. It takes me about five seconds to decide which f-stop is going to work best for any particular shot. It's not arcane in the least.

I seem to keep posting this link, but here it is again, from the LF home page and the article "How to select the f-stop."

https://www.largeformatphotography.info/fstop.html

Heck, if you're lazy or just want the down-and-dirty approach, you don't even have to read the whole article. Just figure out the basic method, print out the tables listed toward the end of the article and paste them on your camera and go to work.

A couple of observations: Most LF lenses work best at or close to f/22. So, there's very little reason to shoot at a larger aperture than that unless you want a shallow depth of field and need the larger aperture for that.

However, if you want lots of near and far things in your photographs to be in focus, there is a very good reason to stop down farther than f/22 when you need the depth of field, despite the slight fall off of performance caused by the (very gradual) onset of diffraction degradation.

You have to enlarge a 4x5 negative a lot to notice diffraction degradation from f/32. How many 30x36-inch prints do you make anyway? Heck, 11x14s from negatives made at f/45 exhibit little or no degradation due to diffraction unless you get out your loupe.

So, in practice, you'll be using a small range of apertures between f/22 and f/45, depending on the focus spread. For those scenes that require stopping down a lot, you may want to keep your print size smaller than 16x20 inches.

Measuring focus spread between the nearest and farthest objects you want in sharp focus is simple. Consulting the chart to find the optimum f-stop is also simple.

You wanted a simple approach; well, there it is, staring you in the face. You just need to get past the initial inertia and read through the article. You don't have to figure your own values for circles of confusion or anything; just use the ones the author does and you'll be very well off. You can always revisit and tweak the method if you find you need to later.

Best,

Doremus

Is this the "simple" table your were referring too towards the bottom of the link your provided? So if I understand, you measure the mm distance on the rail between near and far focus point to determine the f stop. If it falls between two, do you use the smaller f stop?

Do you set the focus point half way between the two or use some form of 1/3 - 2/3 ratio?

Could you explain the N value?

Table of optimal fstops (2)
This shows you the best value of the f-stop to use.
D(mm) F N
1 16.6 19.4
2 22.6 27.4
3 32.2 33.5
4 32.6 38.7
5 32.9 43.3
6 45.2 47.4
7 45.4 51.2
8 45.6 54.8
9 45.8 58.1
10 64 61.2

[JMO]

After reading through this entire (interesting) thread, I’m left with one seemingly simple reaction. After one has taken all the time, effort and expense with LF gear of choice to set-up and make an image on a composition (with needed movements and considering DOF and diffraction considerations), why not make the image at more than one f-stop (whenever possible given wind or other conditions)? Admittedly, I use 4x5 gear and not larger and more expensive film, but I usually take 2-3 exposures of most compositions and vary the aperture to be sure I get what I want as far as DOF. When it comes time to print, I use my light table and a good loupe to help me decide which film(s) to work with. I’m mostly doing landscape photography, so not often wanting to isolate focus narrowly with larger apertures than f22; but if I’m going to take more than one exposure I usually start with the best aperture I’ve determined appropriate, and then stop down one and/or two stops (maybe also changing lens filters or other factors as experience suggests).