Lens Result Question

[Peter De Smidt]

The other day, I had a stock developer solution go bad. After I mixed up a new batch, I took a quick picture as a test, using a 10" lens, of a house across the street. Here's the photo:

https://www.dropbox.com/s/zfqrna9c3vw21xy/house-0508.jpg?raw=1

The image was shot at f/11, and I focused on the house number. The camera, a Toyo AX, was leveled by eye, as I didn't have a small level handy. About 1" of front rise was used. Other movements were at their home positions. The lens is listed as covering 5x7".

[Bob Salomon]

To me your new developing solution is out of focus or you have a lens/camera problem.

[Pere Casals]

190604

With the calculator in hand, the roof has to be sharp.

So IMHO there are only two possibilities:

a) Front and rear standards are missaligned

b) Film was not flat in the holder, we don't see the guide casting a shadow at right side... perhaps the sheet was not well loaded, or the sheet was not flat because of other issues.

[Peter De Smidt]

A) is possible, but I've used this camera/screen for decades. B) is unlikely. The lack of a full black border on right is due to cropping in scanning software.

[Jerry Bodine]

190604...

Pere, the lens focal length was 10" (~250mm) and the implied format was 5x7.

Peter, I have no idea why the upper part of the image is out of focus, but a minor point it looks like you're getting some reflection off the edge of the format opening in the camera, as evidenced the slight build-up of density in the lower left corner of the image (likely due to the position of the sun, as it's not apparent in other corners). You may want to "blacken" the format edges.

[Peter De Smidt]

Oops. Sorry. The format was 4x5. (Toyo AX). The lens is listed as covering 5x7". My question, really, is does this look like a "running out of coverage" issue, or something else?

[Jerry Bodine]

Oops. Sorry. The format was 4x5. (Toyo AX). The lens is listed as covering 5x7". My question, really, is does this look like a "running out of coverage" issue, or something else?

Peter, on looking closer there does appear to be slight convergence by aiming camera upward, judging by the vertical edge of house on the left, messing up the DOF. Obviously the foreground trees are too close for DOF.

[Pere Casals]

Pere, the lens focal length was 10" (~250mm)

hmmm , yes... in that case calculed dof is only 8m !

given the near focus the roof can be out of DOF

190608

[Peter De Smidt]

Pere, the lens focal length was 10" (~250mm) and the implied format was 5x7.

Peter, I have no idea why the upper part of the image is out of focus, but a minor point it looks like you're getting some reflection off the edge of the format opening in the camera, as evidenced the slight build-up of density in the lower left corner of the image (likely due to the position of the sun, as it's not apparent in other corners). You may want to "blacken" the format edges.

Hi Jerry, That's from not taking the time to mask the negative when making the scan.

[Two23]

Hi Jerry, That's from not taking the time to mask the negative when making the scan.


Did you look at the actual neg with a loupe? Maybe you have a scanner issue.


Kent in SD

[Peter De Smidt]

Hi, Kent. Yes, I looked at the negative with a loupe. The out-of-focus areas are not from the scanner.

[Mark Sawyer]

To me, it looks like a field curvature issue in the lens, though that would be unlikely on anything but a Petzval or Landscape Lens. Since the house is right across the street and you know the particulars of the camera set-up, I'd try recreating the shot with everything as it was, with special attention to how the issues look on the ground glass.

[Peter De Smidt]

Mark, that's what I'm leaning towards. The lens is a Veritar.

[swmcl]

Hi Peter,

This reminds me of an issue I had with a Super Symmar when the cells became unglued / misaligned. I think the lens will need to be looked at myself.

If I can see correctly, you have some stairs in focus but the out-of-focus areas are radially out from there. The bricks to the left and right should also be in focus as they are a very similar distance away from the camera but they aren't in focus.

Rgds,

[Mark Sawyer]

Mark, that's what I'm leaning towards. The lens is a Veritar.

I think that's the issue. I'm not sure about the Veritar, but portrait lenses often weren't corrected for a flat field. Faster early designs (prior to Jena glasses being used) suffered more from astigmatism, which could be corrected at the cost of curving the focal plane. Also, spherical aberration causes significant focus shift, (did you focus at the taking aperture?) And stopping down a Veritar (or similar lenses) has a different effect on depth of field than with more conventional lenses. As Wollensak said: https://alphaxbetax.files.wordpress.com/2019/03/1952-portrait-veritar-lens.pdf

[Hugo Zhang]

I remember that I had a Vitax lens many years ago that produced similar images. I agree with Mark that the lens probably has a curved, not flat field.

[Peter De Smidt]

I did focus stopped down, and I expected that the portrait lenses were optimized for closer subjects. I was hoping it would also work well for other things, but it doesn't look like it. I'll put it on my Sinar and take a more careful shot sometime soon. I was expecting the "behind the focus point depth of field", but that's what seems missing. The sides of the house are just behind the focus point, whereas nearer elements seem in better focus.

[Two23]

I did focus stopped down, and I expected that the portrait lenses were optimized for closer subjects. I was hoping it would also work well for other things, but it doesn't look like it. I'll put it on my Sinar and take a more careful shot sometime soon. I was expecting the "behind the focus point depth of field", but that's what seems missing. The sides of the house are just behind the focus point, whereas nearer elements seem in better focus.


When you reshoot, find a nice big brick or cinderblock wall and square the film plane up to it perfectly. That should tell you something.


Kent in SD

[Peter De Smidt]

Will do, Kent.

[Mark Sawyer]

After a couple of Martinis, it occurs to me that for all its improved color corrections and AR coatings, the Veritar is still a Verito, a Landscape Lens with a front modifier. Yup, curved field...

I'm always right, and I never lie... :rolleyes:

[swmcl]

Well there you go ...

A lens that is designed to have a curved field. You (should) learn something new every day.

I'm not a betting person so I'll bet there isn't such a thing in 35mm photography !!

Thanks Mark !

[William Whitaker]

Perhaps you should re-shoot when the wind isn't blowing.
And as for focusing on the house number, I can't read it. It looks out of focus to me. But the tree branches are blurred whereas the roofline behind them is [relatively] sharp.

[Bob Salomon]

Well there you go ...

A lens that is designed to have a curved field. You (should) learn something new every day.

I'm not a betting person so I'll bet there isn't such a thing in 35mm photography !!

Thanks Mark !

Do you shoot flat field subjects like a newspaper page on 35mm or 3 dimensional objects like people or landscapes? If the latter then the lenses corrected to reproduce 3 dimensional objects on a 2 dimensional piece of film are corrected for curved field reproduction.

You might look at the specs for the Minox subminiature Cameras, not the Japanese versions. The German and Latvian versions have a fixed 3.5 aperture lens and a curved film plane. They did excellent reproductions of flat objects like documents. And this worked with a lens fixed at wide open!

[Mark Sawyer]

I'm not a betting person so I'll bet there isn't such a thing in 35mm photography !!


I'd bet some of the newer Lomo AF (Artsy-Fartsy) lenses like the "Petzvals" and "Daguerreotype Achromats" made for 35mm have curved field. But among main-stream lenses, yup, by the time 35mm became a legitimate format, lens design had pretty much matured past such things.

[Jim Galli]

Looks to me like your developer was developing and your veritar was veritaring. Like the Verito, the Veritar becomes a lovely soft focus 17" lens when the front element is removed.

[Peter De Smidt]

I imagine it loses some speed doing that?

[Jim Galli]

I imagine it loses some speed doing that?

Yes, of course. Longer focal length, same size hole. f6 becomes f10 ish.

[Mark Sawyer]

Yes, of course. Longer focal length, same size hole. f6 becomes f10 ish.

Yup. One thing about math. It never changes...

But you know, I think I pretty correctly spotted a pretty off-the-beaten-path issue without knowing what lens was involved. I think I deserve a prize of some sort.

Really, this forum needs prizes. And I want one. I don't care what it is, I just want one.

:)

[Jerry Bodine]

Here ya go, Mark. :D :D

[Jim Galli]

Here ya go, Mark. :D :D
Ding ding ding ding ding ding!!

[Mark Sawyer]

Yay! I won! :cool: :cool: :cool:

I'd like to thank all the people who contributed to this thread. Mr. DeMille, I'm ready for my close up! :rolleyes:

[Peter De Smidt]

Some one beat me to it! I was going to send Mark a coupon, but we don't want to risk starting a frenzy to give the most helpful answer.