LF lens "sweet spots"

[Shootar401]

Is there a chart somewhere on here, or online somewhere else that shows a listing of lenses and what apertures they work best at? I know different copies of the same lens can show different results but those are usually the exception. And most copies will fall within a certain range.

I know my Ektar 127mm is great at f/22. But I also hear people love it at 16 and 32.

[diversey]

Did you go to the central park?:)

[Liquid Artist]

Did you go to the central park?:)
I agree!

For me the "Sweet Spot" is wherever I want it to be.
As in if I want a garden chair in focus but everything both behind and in front out of focus that is exactly what I will have.
For me that's more important than a number someone claims is best.

[Shootar401]

Did you go to the central park?:)

I did, but I brought my Rolleiflex, i'm having slow shutter speed issues on my main LF lens at the moment.

[Peter De Smidt]

Take a look at: http://www.hevanet.com/cperez/testing.html

[ic-racer]

Is there a chart somewhere on here, or online somewhere else that shows a listing of lenses and what apertures they work best at? I know different copies of the same lens can show different results but those are usually the exception. And most copies will fall within a certain range.

I know my Ektar 127mm is great at f/22. But I also hear people love it at 16 and 32.

What is your subject. If it is flat, then the lens data mentioned above is very good. Even better would be to test your own system.
If your subject is 3 dimensional, then optimum results can be obtained using the focusing technique of Hansma. In these cases (3-D subjects) lenses are usually used at apertures in which aperture size is the major determinant of sharpness.
If you like blurry pictures, fuzzy pictures or oddball tilt, then your lens sweet spot is going to be highly subjective and personal.

[djdister]

Individual lens "sweet spots" may be very specific to that lens, made in a certain lot, at a certain time. Aside from lenses that are meant to be shot at a wider aperture for spherical aberration effects (soft focus), this general guidance for optimum f stop from Rodenstock is a decent general guide to start with.

128699

[Jiri Vasina]

I don't care where my lenses are sharpest. I decide the aperture used on the depth of focus I intend to have (sometimes considering in relation with possible exposure time and camera movements). If the resulting image works, it was a sweet spot. If it does not...

[Will Frostmill]

I would add that three things that resolution reports will not tell you are:
1. how much vignetting you get, and at which aperture
2. how much distortion you get, and at what distance (e.g. pincushion vs. barrel)
3. how much field curvature you get, and at what distance. (Though resolution reports will let you guess.)

Stopping down cleans up #1 (and #3 to some extent). If you are scanning #1 & #2 are easy to fix.
Your best bet is to look for a clean copy (no scratches on the rear element, no fungus) of a modern (plasmat, usually) lens, and test it at every aperture. If you don't like it, sell it, and buy a different one. Keep doing this until you get the resolution numbers you want.

I have tested at 150mm/5.6 Schneider Componon enlarger lens by mounting it on a macro bellows attached to one of my mirrorless cameras. I checked every aperture, and found that f/6 was probably the sharpest, and f/8 was probably the best compromise between sharpness and contrast. That's quite wide open for most LF work. Used bellows aren't terribly expensive (from KEH, for instance), and the main difficulty you'd face would be getting the right adapter rings to mount your lens. (I was fortunate the Componon had t-mount threads on one end and standard filter threads on the other. Easy to mount either way. Standard Copal threads are another matter.)

The only way to know is to check, but bear in mind stopping down a single stop can be perfectly adequate for a well corrected lens.

The Ektar 127 is a Tessar formula lens meant for a format slightly smaller than 4x5, so corner and edge resolution tends to be iffy. But if you aren't interested in having anything in focus there, what does it matter?

[DrTang]

I think your last line said it all

what may be the sweet spot for my likes may not be for you


me thinks..there is just no way around testing.. although a fuji instant back and instant film may speed the process up

[Bob Salomon]

I would add that three things that resolution reports will not tell you are:
1. how much vignetting you get, and at which aperture
2. how much distortion you get, and at what distance (e.g. pincushion vs. barrel)
3. how much field curvature you get, and at what distance. (Though resolution reports will let you guess.)

Stopping down cleans up #1 (and #3 to some extent). If you are scanning #1 & #2 are easy to fix.
Your best bet is to look for a clean copy (no scratches on the rear element, no fungus) of a modern (plasmat, usually) lens, and test it at every aperture. If you don't like it, sell it, and buy a different one. Keep doing this until you get the resolution numbers you want.

I have tested at 150mm/5.6 Schneider Componon enlarger lens by mounting it on a macro bellows attached to one of my mirrorless cameras. I checked every aperture, and found that f/6 was probably the sharpest, and f/8 was probably the best compromise between sharpness and contrast. That's quite wide open for most LF work. Used bellows aren't terribly expensive (from KEH, for instance), and the main difficulty you'd face would be getting the right adapter rings to mount your lens. (I was fortunate the Componon had t-mount threads on one end and standard filter threads on the other. Easy to mount either way. Standard Copal threads are another matter.)

The only way to know is to check, but bear in mind stopping down a single stop can be perfectly adequate for a well corrected lens.

The Ektar 127 is a Tessar formula lens meant for a format slightly smaller than 4x5, so corner and edge resolution tends to be iffy. But if you aren't interested in having anything in focus there, what does it matter?

Your information is out of date.

Rodenstock's performance curves, many are available on their web site, give MTF as well as distortion curves, fall off curves and color curves. They are all there for the asking.

[John Kasaian]

FWIW, we might as well throw the term optimal into the soup. I've read what's optimal for the 240 G Claron is f/32 and for the 14" Commercial Ektar, f/45

[Mark Sawyer]

The sweet spot on my lenses is always just outside the frame... :(

[Will Frostmill]

Your information is out of date.

Rodenstock's performance curves, many are available on their web site, give MTF as well as distortion curves, fall off curves and color curves. They are all there for the asking.

So, are they calculated performance, or measured?

[Old-N-Feeble]

The sweet spot on my lenses is always just outside the frame... :(

Huh? I always considered the sweet spot in your images precisely where Tink sits.

[Vaughn]

Huh? I always considered the sweet spot in your images precisely where Tink sits.

Most assuredly! But as primarily a photographer of the light on the landscape, the sweet spot is where I set up the camera! :cool:

[John Kasaian]

Most assuredly! But as primarily a photographer of the light on the landscape, the sweet spot is where I set up the camera! :cool:
+1

[Ken Lee]

You can easily see for yourself: focus with a magnifying loupe and slowly adjust the aperture on the lens: you'll see that performance increases as you stop-down from wide-open, reaches a maximum and then declines.

On most LF lenses, the sweet spot is f/16 to f/22.

[Kevin Crisp]

I think Ken is correct. But, if you take notes, then some day when you have a negative that seems just extraordinarily sharp to you, you can check your exposure data and see what the aperture was.

All my lenses are plenty sharp from f:16 to f:32. At f:45 yes, I can see diffraction working against me (with a loupe) but in a print 16X20 or smaller the print will be fine whether shooting 4x5 or 5x7. Below f:45, a region I have visited just a couple times, the negative was sharp enough.

In the field though I would never be governed by working around (or to) some "sweet spot" on a particular lens. I use depth of field considerations and movements as necessary to get the parts sharp I want sharp in the f:16 to 32 range.

[Vaughn]

No lens has a sweet spot if on a shaky camera on a wobbly tripod!


In the field though I would never be goverened by working around (or to) some "sweet spot" on a particular lens.

True! But also I had to learn not to automatically go for f64 or f128. I got into that habit photoing in the Redwoods where the complexity of the scene does not allow much movements and DoF needs great.

Scanned Carbon Print
4x5, 150mm, TMax100

[Drew Wiley]

Each lens is at its best when the image on the groundglass looks best with that particular subject at that precise moment in time. If the light isn't quite right yet, take your charts and build a bonfire to roast marshmallows over, until things are right.

[Bob Salomon]

So, are they calculated performance, or measured?

They test.

[Dan Fromm]

If the light isn't quite right yet, take your charts and build a bonfire to roast marshmallows over, until things are right.

But not under a natural arch.

[Old-N-Feeble]

But not under a natural arch.

:D

[Jac@stafford.net]

The sweet spot of my favorite lens is in Rhode Island. I live in Minnesota.