Lens sweet spot

bluefin · Sep 7, 2007

I'm brand new to LF and just got my equipment from KEH today!

I would like to know where the sweet spot is on each of the 3 lenses I bought.

Schneider-Kreuznach APO-Symmar f5.6/210mm

Schneider-Kreuznach APO-Symmar f5.6/150mm

Schneider-Kreuznach Super-Angulon f8/90mm

If they are miserable lenses please don't tell me. Lie!

Thanks in advance for saving me some film and even more important, those fabulous images I have yet to capture......Mark

Doyle Thomas · Sep 7, 2007

All are great lenses, The sweet spot is always the center of any lens.
I had a Schneider-Kreuznach Super-Angulon f8/90mm, tack sharp with 1/2 stop extension. I traded up to the multi-coated 5.6 some time ago, always regretted it.

Doyle

keithwms · Sep 7, 2007

Sweet spot? All spots are sweet in LF! Well, almost...

Many LF lenses will attain optimal image circles and resolution when stopped down to f/16 or f/22 or so. But your enlargement factor is so small with LF that when you look at your final print, you are very unlikely to see much variation in performance from one aperture to the next, except for falloff.

Enjoy!

bluefin · Sep 7, 2007

keithwms said:
Sweet spot? All spots are sweet in LF! Well, almost...

Many LF lenses will attain optimal image circles and resolution when stopped down to f/16 or f/22 or so. But your enlargement factor is so small with LF that when you look at your final print, you are very unlikely to see much variation in performance from one aperture to the next, except for falloff.

Enjoy!

Thanks guys. I'm sure I'll have lots more questions so thanks for the info and the nice welcome to LF.

dslater · Sep 7, 2007

Doyle Thomas said:
All are great lenses, The sweet spot is always the center of any lens.
I had a Schneider-Kreuznach Super-Angulon f8/90mm, tack sharp with 1/2 stop extension. I traded up to the multi-coated 5.6 some time ago, always regretted it.

Doyle

Why did you regret trading up?

k_jupiter · Sep 8, 2007

Those lens be crap. But... because I like you, I will trade you some fine examples of LF Wollensak Raptars, and a couple of fine Zeiss Tessars for those miserable pieces of glass. I will use them as paperweights, but you won't have the heartbreak of shooting film through those coke bottle lens.

Send me a p-mail and I'll set up the transfer.

*L*

tim in san jose

bluefin · Sep 8, 2007

k_jupiter said:
Those lens be crap. But... because I like you, I will trade you some fine examples of LF Wollensak Raptars, and a couple of fine Zeiss Tessars for those miserable pieces of glass. I will use them as paperweights, but you won't have the heartbreak of shooting film through those coke bottle lens.

Send me a p-mail and I'll set up the transfer.

*L*

tim in san jose

Thanks K.....Your generosity overwhelms me!

Dan Fromm · Sep 8, 2007

Um, bluefin, what difference does it make? I ask because although I like image quality as much as the next person, I've never understood why the image that's sharpest in the plane of best focus should be the best of all possible images with same composition etc. And you've asked at which aperture your lenses are sharpest in the plane of best focus. I wish getting an image that satisfies were that simple.

papagene · Sep 8, 2007

Mark, those are all very nice lenses, such that all you need to do is go out and have fun learning LF photography.

gene

Doyle Thomas · Sep 8, 2007

I had a Schneider-Kreuznach Super-Angulon f8/90mm, tack sharp with 1/2 stop extension. I traded up to the multi-coated 5.6 some time ago, always regretted it.

Hard to describe, I think that because the new 5.6 lens is more neutral it lacks the "character" of the older 8.0

Doyle

bluefin · Sep 8, 2007

Dan Fromm said:
Um, bluefin, what difference does it make? I ask because although I like image quality as much as the next person, I've never understood why the image that's sharpest in the plane of best focus should be the best of all possible images with same composition etc. And you've asked at which aperture your lenses are sharpest in the plane of best focus. I wish getting an image that satisfies were that simple.

Dan, I understand your point completely. There are some images (not all) that I like to be tack sharp throughout the entire image. I have found some of my fast 35mm glass to be exceptionally sharp at f5.6 to f8. I call this the sweet spot and always tried to keep the lens capabilities (limitations) in mind when shooting. With a DSLR I can do as many exhaustive tests as I like to determine what those strengths and weakness are. With a 4x5 I'm more dependent on people with experience than my own tests.

We are moving way out of my level of experience however, my question was not dependent on the plane of focus. It was directed more on the impact to light, such as diffraction, as the aperture changed.

If i'm making an error here please let me know......Mark

dslater · Sep 8, 2007

bluefin said:
Dan, I understand your point completely. There are some images (not all) that I like to be tack sharp throughout the entire image. I have found some of my fast 35mm glass to be exceptionally sharp at f5.6 to f8. I call this the sweet spot and always tried to keep the lens capabilities (limitations) in mind when shooting. With a DSLR I can do as many exhaustive tests as I like to determine what those strengths and weakness are. With a 4x5 I'm more dependent on people with experience than my own tests.

We are moving way out of my level of experience however, my question was not dependent on the plane of focus. It was directed more on the impact to light, such as diffraction, as the aperture changed.

If i'm making an error here please let me know......Mark

Hi Mark,
the thing is that with LF, your enlargement factor is much less - 2x instead of 8x for an 8x10 print. As a result, the sharpness of the lens is much less important than it is for 35mm.
When you're shooting, I think you will find you usually need to stop down past the sweet spot to get enough DOF - but it won't matter - at 2x enlargement, you'll never see the difference. Even at larger enlargements, you still won't see the difference because at that point the print is so large, you need to view it from further away.
Dan

Tom Duffy · Sep 8, 2007

bluefin said:
I'm brand new to LF and just got my equipment from KEH today!

I would like to know where the sweet spot is on each of the 3 lenses I bought.

Schneider-Kreuznach APO-Symmar f5.6/210mm

Schneider-Kreuznach APO-Symmar f5.6/150mm

Schneider-Kreuznach Super-Angulon f8/90mm

If they are miserable lenses please don't tell me. Lie!

Thanks in advance for saving me some film and even more important, those fabulous images I have yet to capture......Mark

Congratulations on your purchases. I can't speak to the 90mm. I have 210 and 300 APO-Symmars. They are my favorite lenses. They are sharp enough at most usable apertures. I think you will find the sweet spot at f11 to f16. But... The large format aesthetic is everything near to far should be in focus (exceptions, of course, such as portraiture). This usually necessitates shoot at smaller apertures. I wouldn't generally shoot smaller than f32 because diffraction starts to affect sharpness. It is relative, however, a 4x5 taken at f64 printed to 8x10 will be way sharper than a 35mm picture taken with a 50mm lens at f8.

What kind of camera do you have? If it's wooden you may find you have to shoot at f22 to keep all the corners sharp simultaneously.

Take care,
Tom

Scott Peters · Sep 8, 2007

Start at f22 and go from there...perhaps shoot some transparencies and try f16 and f32 on the same image for 'kicks and giggles' to see what you 'like'. I think you will find the right balance at f22, i.e. sharp and corners, etc.

bluefin · Sep 8, 2007

Tom Duffy said:
Congratulations on your purchases. I can't speak to the 90mm. I have 210 and 300 APO-Symmars. They are my favorite lenses. They are sharp enough at most usable apertures. I think you will find the sweet spot at f11 to f16. But... The large format aesthetic is everything near to far should be in focus (exceptions, of course, such as portraiture). This usually necessitates shoot at smaller apertures. I wouldn't generally shoot smaller than f32 because diffraction starts to affect sharpness. It is relative, however, a 4x5 taken at f64 printed to 8x10 will be way sharper than a 35mm picture taken with a 50mm lens at f8.

What kind of camera do you have? If it's wooden you may find you have to shoot at f22 to keep all the corners sharp simultaneously.

Take care,
Tom

Tom,

Thanks for the info.

I bought a Sinar F2 View Camera. It's in excellent shape, as are the lenses.

Dan Fromm · Sep 8, 2007

Mark, to get some idea of what can be achieved in the way of resolution with a variety of LF lenses, some new, some quite old, and how it varies with aperture, visit http://www.hevanet.com/cperez/testing.html .

You have a very nice set of lenses, just go use them and don't worry. As has been pointed out, LF negs aren't enlarged as much as 35 mm negs so don't need as much resolution.

Handy rule of thumb: a lens can't resolve more than around 1500/f# lp/mm. On-film resolution will be worse. A print that looks sharp at normal viewing distance has to resolve at least 8 lp/mm. Max enlargement to get a nice sharp print is, therefore, max resolution on film/8. Play around with the numbers, then look at the results in the lens tests I've directed you to.

FWIW, since I have Nikons and odds and ends to fit them, I do acceptance tests of newly-arrived LF lenses' central sharpness (long story, that's usually all I have to worry about) with a Nikon, bellows, tubes, adapters, ... Cheap, often informative.

John Kasaian · Sep 8, 2007

bluefin said:
I'm brand new to LF and just got my equipment from KEH today!

I would like to know where the sweet spot is on each of the 3 lenses I bought.

Schneider-Kreuznach APO-Symmar f5.6/210mm

Schneider-Kreuznach APO-Symmar f5.6/150mm

Schneider-Kreuznach Super-Angulon f8/90mm

If they are miserable lenses please don't tell me. Lie!

Thanks in advance for saving me some film and even more important, those fabulous images I have yet to capture......Mark

Bluefin,

The sweet spot is directly above the tripod where you've set up your camera

bluefin · Sep 9, 2007

Dan Fromm said:
Mark, to get some idea of what can be achieved in the way of resolution with a variety of LF lenses, some new, some quite old, and how it varies with aperture, visit http://www.hevanet.com/cperez/testing.html .

You have a very nice set of lenses, just go use them and don't worry. As has been pointed out, LF negs aren't enlarged as much as 35 mm negs so don't need as much resolution.

Handy rule of thumb: a lens can't resolve more than around 1500/f# lp/mm. On-film resolution will be worse. A print that looks sharp at normal viewing distance has to resolve at least 8 lp/mm. Max enlargement to get a nice sharp print is, therefore, max resolution on film/8. Play around with the numbers, then look at the results in the lens tests I've directed you to.

FWIW, since I have Nikons and odds and ends to fit them, I do acceptance tests of newly-arrived LF lenses' central sharpness (long story, that's usually all I have to worry about) with a Nikon, bellows, tubes, adapters, ... Cheap, often informative.

Dan, Thanks for the info. The lens tests were very interesting....Mark

Lens sweet spot

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