Aspherical lenses availability

[simdil]

Hello, I am a newbie in the matter of large format photography and I would like to replace my 150mm lens with an aspherical one, since I am experiencing distorion to my images.
I did my research and as far as I could find out, the only aspherical lenses with copal shutter were made by Schneider Kreuznach (series Super Symmar XL).
Those series are now discontinued and I am having trouble to find good alternatives and good offers on Ebay (I live in EU).
Can you suggest me any alternative to the Super Symmar XL for my 4x5" camera? Did I get it wrong that Schneider Kreuznach Super Symmar XL are the only aspherical lenses available?
Thank you and have a nice time.

[mdarnton]

First, what kind of distortion are you experiencing? That doesn't sound right. Any good lens should have virtually none.

Second, if you really do have a oerceivable distortion problem, in a general way apo process lenses won't have any, some more than others, and they'll be a lot cheaper. There's even a special apo-Artar for mapmaking with virtually no distortion at all.

[Oslolens]

I suspect you are experiencing distorsion only on three-dimensional subjects? If so, change to a longer lens and move backwards to avoid it.

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[simdil]

Thank you all for the hints. I am not able to say which kind of distortion. I assume it is spherical aberration, since it happens in particular in the the peripheral part of the frame. I even wonder whether I am doing something wrong with the camera controls... As I said, I am a newbie.
I have attached one shot where the subject (tower) appers wonky and the shpere is stretched (low res compressed jpg). Lens: Schneider Kreuznach Symmar-S 150mm


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[Bob Salomon]

Lots of lenses use at least one aspherical element. Check the Apo Sironar W and S series from Rodenstock.

[Dan Fromm]

OP, you have slight barrel distortion. This is an off-axis aberration that can be reduced by stopping down.

What lens(es) did you use to take those pictures? What aperture(s) did you shoot at?

[Oslolens]

I suspect you are experiencing distorsion only on three-dimensional subjects? If so, change to a longer lens and move backwards to avoid it.

Sent fra min SM-G975F via TapatalkYes, I was right ;) Alternative way to avoid this is to move camera to have the three-dimensional subject closer to center. This will happen with any lens and at any aperture as long as you put it out there. It will look even worse when the subject is a face of a person :)

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[simdil]

Thank you, I will search. I´ve never considered Rodenstock, so far.

[simdil]

OP, you have slight barrel distortion. This is an off-axis aberration that can be reduced by stopping down.

What lens(es) did you use to take those pictures? What aperture(s) did you shoot at?

I used a Schneider Kreuznach Symmar-S 150mm, I shot at f/16 1/15 sec., due to windy weather condition.
Thanks for the tip, I´ll try to stop down.

[simdil]

Yes, I was right ;) Alternative way to avoid this is to move camera to have the three-dimensional subject closer to center. This will happen with any lens and at any aperture as long as you put it out there. It will look even worse when the subject is a face of a person :)

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I see. So this will happen regardless of using a aspherical lens specifically designed to avoid such distortions?
I had no idea, thank you.

[Bernice Loui]

Stopping down more than f16 is not going to reduce distortion of the spherical object in your image. Using a longer focal length lens (say 300mm) and backing up lots will help. The other factors is camera position. Appears the image was made at ground level which can alter the geometric shape of a round object being imaged on to a flat sheet of film. If possible, try setting up the camera from a location that places the spherical object on axis with the lens. Might not be possible, but suspect this will make a significant difference using the same 150mm lens.

As for geometric distortion of view camera lenses of the modern variety (Schneider Symmar S ) it is very low, but how they are used and shape of objects being imaged will have an effect of how the object being imaged transfer on to a flat sheet of film.

As for Aspheric lensed for LF, there were only ~one~ series of lenses made in volume production for LF photograph, they are the Schneider Super Symmar XL series which are wide angle lenses. Any wide angle lens would very likely make this distorting worst due to the shorter focal length.

Found the Schneider data sheet for the APO Symmar which is the later variant of the Symmar S, honestly they are not that different for distortion spec. Distortion is not more than 0.5% which is typical for lenses of this type and generic formulation. If there is a need to achieve lower geometric distortion, use a "APO" process lens they have much lower distortion, but in this specific image case, the possibility of lower the geometric distortion of the spherical object of using an extremely low geometric distortion APO process lens is not good. Longer focal length and camera position will change this distortion of the spherical object.
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Bernice

[ic-racer]

I am experiencing distorion to my images...
I did my research and as far as I could find out...

More research is in order.
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[Oslolens]

In my head it would make a difference if lens and film plane is directed directly towards the sphere, then shift the lens plane (or film plane if available) to make a more interesting picture, as opposed to what you have been doing. Also take note of differences of circle vs sphere when it comes to how it look on film when film plane and circle is parallel, shown on picture above. This is what made the copy camera work. My LF teacher missed out on this, borrowed my 180mm Fujinon-W with less sharp corners on 8x10", as opposed to use a wide angle 150mm to achieve sharp corners.

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[Bernice Loui]

Since the Schneider data sheets were out, here is the 240mm f9 APO Artar (Originally Goerz process lens) for comparison. It's geometric distortion is virtually nil. Yet if the same focal length (150mm, will not properly cover 4x5, image circle is too small) APO Artar or similar process lens geometric distortion of the spherical object will not change.

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Bernice

[simdil]

Stopping down more than f16 is not going to reduce distortion of the spherical object in your image. Using a longer focal length lens (say 300mm) and backing up lots will help. The other factors is camera position. Appears the image was made at ground level which can alter the geometric shape of a round object being imaged on to a flat sheet of film. If possible, try setting up the camera from a location that places the spherical object on axis with the lens. Might not be possible, but suspect this will make a significant difference using the same 150mm lens.

As for geometric distortion of view camera lenses of the modern variety (Schneider Symmar S ) it is very low, but how they are used and shape of objects being imaged will have an effect of how the object being imaged transfer on to a flat sheet of film.

As for Aspheric lensed for LF, there were only ~one~ series of lenses made in volume production for LF photograph, they are the Schneider Super Symmar XL series which are wide angle lenses. Any wide angle lens would very likely make this distorting worst due to the shorter focal length.

Found the Schneider data sheet for the APO Symmar which is the later variant of the Symmar S, honestly they are not that different for distortion spec. Distortion is not more than 0.5% which is typical for lenses of this type and generic formulation. If there is a need to achieve lower geometric distortion, use a "APO" process lens they have much lower distortion, but in this specific image case, the possibility of lower the geometric distortion of the spherical object of using an extremely low geometric distortion APO process lens is not good. Longer focal length and camera position will change this distortion of the spherical object.
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Bernice



Really thanks for such detailed and precious info.

[simdil]

In my head it would make a difference if lens and film plane is directed directly towards the sphere, then shift the lens plane (or film plane if available) to make a more interesting picture, as opposed to what you have been doing. Also take note of differences of circle vs sphere when it comes to how it look on film when film plane and circle is parallel, shown on picture above. This is what made the copy camera work. My LF teacher missed out on this, borrowed my 180mm Fujinon-W with less sharp corners on 8x10", as opposed to use a wide angle 150mm to achieve sharp corners.

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Thanks for the suggestion. Actually I had to tilt the lens standard toward the tower in order to increase DOF. But I didn't notice any change in the geometry, overall.

[Doremus Scudder]

Objects at the edge of the field will always have this kind of distortion to a certain degree (depending on the focal length of the lens) simply due to the fact that you are projecting the image on a flat surface (the film). That stretches and distorts the edges kind of like the way the continents are stretched on a map projection (Greenland really isn't bigger than Australia...).

There's nothing wrong with your lens and an aspherical lens won't help here. Moving back and using a longer focal length lens or recomposing the image (or living with the distortion) are about all you can do.

BTW, aspherical lenses allow complex lens designs and designs with fewer elements. However, Plasmat designs, like your 150mm Symmar are well corrected for distortion and chromatic abberation.

Best,

Doremus

[simdil]

More research is in order.
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Thank you so much, it´s a very precise example.

[Drew Wiley]

Longer lens. It's that simple.

[simdil]

Longer lens. It's that simple.

What focal length would you suggest, let's say for the same picture, in place of my 150mm?

[Corran]

What focal length would you suggest, let's say for the same picture, in place of my 150mm?

A more important question for you is whether or not there is room to move back significantly and whether or not your intended composition and arrangement of items in the frame will be possible with a different focal length (or by changing angle, using shift to move the circular building off-center, etc.).

There's no free lunch here.

[Dan Fromm]

To expand a little on Bryan's response, distortion is an off-axis aberration. The farther off axis, the worse it is.

With that in mind, compose with the vertical spire (what is it?) nearer to the center of the frame.

I don't understand the suggestion to use a longer lens. Would one of the people who made it please explain how and why that would help?

[Drew Wiley]

Even a 180 should resolve most of that issue.

[Oslolens]

To expand a little on Bryan's response, distortion is an off-axis aberration. The farther off axis, the worse it is.

I don't understand the suggestion to use a longer lens. Would one of the people who made it please explain how and why that would help?
If you are to have the same elements in the picture, move backwards with a longer lens. Figure 34 of page 40 shown above shows the effect of moving the tennis ball towards the center.


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[Ken Lee]

http://www.kennethleegallery.com/images/forum/WideAngleClose.jpg

This photo was taken at very close distance with a very wide angle lens (14mm) on a full-frame camera.

These individuals may appear to have Dolichocephaly (https://en.wikipedia.org/wiki/Dolichocephaly) but in fact it's only an apparent stretching due to projection, as described by Doremus.

[simdil]

If you are to have the same elements in the picture, move backwards with a longer lens. Figure 34 of page 40 shown above shows the effect of moving the tennis ball towards the center.


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Based on Figure 34 of page 40 shown above, shouldn´t the focal lenght be irrelevant as long as the sphere subject is positioned towards the center?

[Oslolens]

Based on Figure 34 of page 40 shown above, shouldn´t the focal lenght be irrelevant as long as the sphere subject is positioned towards the center?Yes, you are right. Back to your pictures, if the sphere is going to be positioned that far out, backing up, the sphere will look more round. To keep the sphere and the building in picture, you need a longer lens, or use a part of the negative -cropping.

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[Doremus Scudder]

To expand a little on Bryan's response, distortion is an off-axis aberration. The farther off axis, the worse it is.

With that in mind, compose with the vertical spire (what is it?) nearer to the center of the frame.

I don't understand the suggestion to use a longer lens. Would one of the people who made it please explain how and why that would help?

Dan,

It's the off-axis angle that determines the extent of the distortion. Since longer lenses see and project a more acute angle, the subsequent off-axis distortion at the same distance off axis is less. Hope that's clear.

Doremus

[Corran]

An illustration of two focal lengths showing the difference in angles. Consider the angle of the film/back to the spherical object in frame.

http://www.esearing.com/Bryan/AV/photosharing/camera-focal-length-angles.jpg

My issue with the suggestion of longer focal lengths is that, in my experience, backing up and getting the same or even similar composition is very unlikely, if even possible (something in the way, or a hill makes the height change, or an errant tree is in the composition suddenly). This also messes up the size relationships if you have anything in the foreground.

[Armin Seeholzer]

Even a 180 should resolve most of that issue.

No almost not visible, but with 300mm it would be a bit better!