Nikon 90mm 4.5 - A case of the Bends, any advice?

[bohngy]

Dear Large format peeps,

I'm trying to shoot some interior portraits, generally in small spaces (i.e. no more than about 2-3meters from my subject) and wanted a wide angle perspective to grab a bit of the environment in my frame.

I've pushed the boat out and bought a Nikon 90mm 4.5, as I had heard many excellent things about it. However I'm distraught at the distortions this lens (and presumably all 90mm lenses on 5x4) create at these close focusing distances. People's hands become massive in the center of the frame, and feet stretch out comically to the edges. I've never seen distortions so bad, I frequently use a Mamiya RZ with a 50mm lens - both work out to be a 24mm equivalent and the 50mm mamiya lens is excellent.

I'm battling to get some usable shots at the moment, I'm sure the distortions are showing on the groundglass, but just trying to focus in poor light and keep my subject interested at the same time is proving VERY tricky! :(

If anyone could offer some advice I would be very grateful.

[Mike1234]

Your math is pretty close but your vision must be affected as you view on the GG vs. however you're viewing with your RZ. The distortion should be about the same. Are you working closer to your subject with the 4x5? Same "exact" subject matter, framing, working distance, etc?

[JimL]

The "stretching" of features is inherent to rectilinear lenses. Combine that with the exaggeration of size between near and far objects with wide angle lenses, and that's what you'll get. Bill Brandt used this effect to the max. To reduce the effect, you'll have to reduce the size of your subject in the frame. Or look under "distortion" on the ptlens (http://epaperpress.com/ptlens/) site for a suggested photoshop correction.

[bohngy]

Thanks for the reply Mike, so the distortion should be about the same right? because the lenses have a (roughly) equivalent field of view?

Either way, I'm going to have to move to 67 for this project I think. I still can't explain the optical distortions.
Here's a picture that show's a mild example of the distortion, it's been much worse at times. the hand is fat and her knee is... in a word... horrible. Suffice to say, I've never observed such a severe problem with my 50mm on the mamiya RZ.

Is there any fault in my working process that could lead to this... other than focussing so close, which is unavoidable.

[Mike1234]

Yes, they have about the same FOV. I can only guess it's the pose, working distance or cropping. Or... maybe you should dig out more similar examples from your RZ w/ 50mm and compare them.

[Peter K]

Either way, I'm going to have to move to 67 for this project I think. I still can't explain the optical distortions.
This isn't optical distortion but perspective forshortening. If you take three pictures from the same point of view, the front lens is at the same place, with a 35mm camera and a 24mm lens, with your RZ and a 50mm lens and with the 90mm lens on 4x5" and enlarge every neg let's say on 8x10" you will get the same perspective forshortening on every image.

Possible you can remember the kids-play looking in each other's eye from such a short distance both nose-tips are touching? (Older people can't do this anymore because of "myopia", lesser flexibility of the eye's lens.) Why? Because with this perspective forshortening is at it's maximum.

Peter

[Andre Noble]

bohngy, perhaps this is the type of distortion you are referring to: http://www.dxo.com/us/photo/dxo_optics_pro/optics_geometry_corrections/anamorphosis

There is normal distortion (perspective) and abnormal distortion (rectilinear). The Nikon 90 SW lens does not have the latter.

[Bob Salomon]

Foreshortening means that objects closer to the lens are reproduced larger then objects further from the lens. This is true for all lenses but the shorter the focal length the more pronounced it will be. This is also true for all formats.
For your problem you need to move further away from the subject, or control the placement of the closer objects to reduce this effect or use a longer lens. Creative lighting can also be used to de-emphasize the enlarged features.

Foreshrtening will also create enlarged noses, foreheads, ears, etc. so it is important when using a short lens that you control the lens/camera placement in relation to the subject.

If you were to photograph a round object, plate, ball, etc. it would not be round due to this effect so one way to learn how to control foreshortening would be to photograph a basketball at the distances that you are trying to shoot and use lighting and camera angles to control/mask the foreshortening.

[Mike1234]

I just never use a WA on standard portraits unless it's a group shot and I have not choice due to distance restrictions. OTOH, if I WANT the distortion for some reason then I'll use a WA. Yes, some very famous photographers used normal or even wide lenses for portraits but I don't like the distortion on most subjects (normal "flattering" protraits).

[timparkin]

I could well be the *lack* of distortion in the large format lens which is causing the problem. Possible barrel distortion in the medium form lens could ameliorating natural perspective distortion? Also, the focal point in a large format camera is very close to the front of the lens; is this so for your medium format camera? If you are just getting 'as far into the corner as possible', the large format lens focal point will be further into the room than the medium format cameras (especially if you have to get behind the GG screen). any/all of these relevant?

[Armin Seeholzer]

There is also this pupil trick to get to cos4 which is used on the LF wide's which make this happen more pronounced!
I did a test re. distorsion with to the 155 Apo Grandagon against a 150 Symmar S on 4x5 inch and the Grandagon shows much more distorsion at the corners and at the outside of the picture frame and this is with short distances even more pronounsed!

Cheers Armin

[Peter K]

There is also this pupil trick to get to cos4 which is used on the LF wide's which make this happen more pronounced!
As you can see here (http://www.rodenstock-photo.com/en/main/products/lenses-for-analog-photography/apo-grandagon/) the Apo-Grandagon has less than 0.5 % distortion. With other lenses from the same type like the Biogon from Zeiss, the Aviotar and the Super-Aviogon from Wild, but all designed from L. Berthele, the distortion is less than 0.1 %.

I did a test re. distorsion with to the 155 Apo Grandagon against a 150 Symmar S on 4x5 inch and the Grandagon shows much more distorsion at the corners and at the outside of the picture frame and this is with short distances even more pronounsed!
This lenses are very sensitive for the image scale. Used for close-ups there isn't only distortition visible but also color fringes.

But all this has nothing to do with the perspective forshortening seen on the OP's image.

Peter

[Armin Seeholzer]

Hi Peter

Just want remember you on the tread on german LF forum, where GPO just stated this more distorsions from GF wide angel he used for pack shoots and stillife and I did not belive it, till I did my on test as above!

Happy new year, Armin