Optimized aperture

[Songyun]

Where can I find the information of optimized aperture of certain lens? Is it always f22? I remember seeing Docter 240 optimized at f 16, and Rodenstock Apo sironar s series optimized at f 16. How about nikon M series, fuji C series, and fuji A series?

[cotdt]

you can shoot them wide open, and they would still be sharp. it's a matter of how much DOF you want.

[Murray]

Probably varies with application, although your question is surely directed toward pictorial use in the field.

I think f/22 is probably fairly consistent for graphic arts process lenses. With those lenses often being in the f/9 range (except for very long f.l. ones), that suggests more than 3 stops down from wide open.

Smaller format lenses it's common for roughly 2 stops down from wide open to be 'best'. (Someone told me Kodak Medalist Ektar f/8-11 despite being f/3.5 wide open).

Tessars f/11 or higher to keep corners sharp, but don't know where resolution is best.

Application-specific special lenses like certain aerial recon lenses supposedly optimal (or maybe 'as good as') wide open. Projection lenses and point source enlarging lenses are used wide open (maybe for other reasons, and may not even have an adjustable aperture).

Sounds like you're an LF person anyway (you're here, and the lenses you asked about sound like it too), so you're probably aware format plays some role. 35mm would be into diffraction limits probably at f/22.

I have a monochromatic 15"x21" format graphic arts lens that is f/8 max and was told for that particular lens f/9.5 was the 'sweet spot'.

Probably not what you were asking for, but hopefully something of interest.

Murray

[vinny]

You may get all sorts of anwers. I've heard guys say"just stop it down as far as you can get way with" which is fine for magazine publication or contact prints in some cases but i don't know many who make a living shooting that way. There's a chart on the net somewhere with lens test data that a couple guys did. I googled and found this:
http://www.hevanet.com/cperez/testing.html
it shows center and edge sharpnes at various apertures. it should give you an idea.

[cotdt]

"optimized aperture" is meaningless when a good lens can give you the same 60 lp/mm from wide open at f/4.5 down to f/22. beyond that, diffraction limits resolution.

[Gordon Moat]

Seems like many modern lenses, going by results from C. Perez (et al), is near f16. In theory, shooting more wide open could get better results, though I think lens construction limits that on many lenses. My personal choices (with 4x5) is to shoot at f11 or f16, though I have shot wide open or f8 quite often. Many times either selective focus or a desire to have more in focus, dictates my choice in aperture.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Peter K]

The aperture is related to the focal-lenght, f/x, so the with longer focal-lenghts the aperture can be smaller with longer lenses before diffraction influences the image. Up to the fourties of the last century LF lenses where optimized for f/22, but later the optimum diaphragm was, and is, f/16. Diffraction optimized lenses, such ones used for micro-electronis, work at best wide open. But with normal lenses on can correct small residual faults by stopping down the diaphragm.

Try it with your lens, it's the easiest way to find out.

[Ron Marshall]

Where can I find the information of optimized aperture of certain lens? Is it always f22? I remember seeing Docter 240 optimized at f 16, and Rodenstock Apo sironar s series optimized at f 16. How about nikon M series, fuji C series, and fuji A series?

Lens test data at f11, f16 and f22:

http://www.hevanet.com/cperez/testing.html

[Dave_B]

Folks:
Roughly a year ago View Camera magazine had a couple of articles by Robert Hallock who showed how one can calculate this. The basic idea is that as the aperture gets smaller, things like spherical aberation get better but at some point diffraction takes over and dominates. Typically f16-22 is best for many LF lenses but he shows how to calculate it exactly.
Cheers,
Dave B.

[Armin Seeholzer]

My APO Symmar 210mm is sharpest at f 11 but I can very seldom use f 11 because I need more DOF!
So always stop so much down as you need to!

Cheers Armin

[uniB]

I was told by pretty reasonable landscape photographer Joe Cornish that you can get away with up to f32 1/3 although I notice with most of his work he opts for around f22. I'd have thought with camera movement you don't need anything above f22 very often anyway.

[Songyun]

Thanks everyone for the input. I will bookmark the link.

[Peter K]

My APO Symmar 210mm is sharpest at f 11 but I can very seldom use f 11 because I need more DOF!
So always stop so much down as you need to!
Such quality lenses cannot stopped down infinitely, only up to the f-stop diffraction is no issue. So rember the group of the famous photographers called "f-64" :cool:

[Dan Fromm]

Folks, take a look at http://www.vanwalree.com/optics.html, page down to text that begins "The below figure and table illustrate the dependence of third-order lens aberrations" He's got it wrong, diameter isn't what matters, it is relative aperture (our familiar f/number). But note the dependencies.

The aperture that gives the best sharpness across the desired field in the plane of best focus depends on the field's width and the lens' design. No lens is perfect, most but not all lenses are worst wide open because of the difficulty of getting good correction at large apertures. Stopping down reduces some aberrations and increases the diameter of the field with good sharpness. Stopping down also increases loss of sharpness to diffraction. So at some aperture gains from reduction of residual aberrations are more than offset by losses to diffraction; from there down, stopping down reduces sharpness in the plane of best focus.

All this depends on the lens' design. There are, by the way, lenses designed to be sharpest wide open. I have some, e.g., Zeiss Luminars, Reichert Neupolars. And some aerial camera lenses, e.g., some very strange Petzval derivatives made by, IIRC, Fairchild, are best wide open. Most aerial camera lenses, though, improve for a while as they're stopped down.

All that said, optimality depends on purpose. We don't go out to get best sharpness, we go out to shoot images that please. It can make sense to trade off sharpness in the plane of best focus for improved sharpness out of the plane of best focus. And fuzzy images can please too. The best aperture to use in a situation depends on the photographer's goals, it isn't inherent in the stupid lens.

Peter, members of the school of f/64 didn't shoot at that ridiculous aperture, they used the number to symbolize their ideal of image quality -- sharp everywhere. They rose in opposition to the pictorialist school, whose aim was, crudely, to produce black and white watercolors by photographic processes. Soft everywhere.

[timparkin]

I was told by pretty reasonable landscape photographer Joe Cornish that you can get away with up to f32 1/3 although I notice with most of his work he opts for around f22. I'd have thought with camera movement you don't need anything above f22 very often anyway.

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

This resource is quite helpful... It suggests that the f32 1/3 is the limit for 20x24's for 4x5 (which is one of Joe's largest size prints on sale - apart from specials).

This page

http://www.hevanet.com/cperez/testing.html

suggests that f16 is the optimum aperture for most lenses.. (I scanned down and couldn't see many that weren't f16)

I think most people would say 10x is the maximum enlargement that most formats will take and hence from the first referece, you should be targeting f22 if possible..

Tim

[Peter K]

Dan, also when Luminars are used with LF camera microscopes like the Ultraphot, the focal lengts are small and any smaller aperture reduces the numerical aperture and the resolution. But with focal lenghts normaly used with LF cameras f/64 is an option, specially when the negative is contact printed like by Weston, Cunningham and others of the group f/64.

[Jim Jones]

Long ago I relied on stopping older untested normal lenses down to an entrance pupil of about 6mm for the best compromise between diffraction and lens abberations. One can disregard the frocal length in this rule of thumb. Modern lenses have come a long way since then.