7 1/2 inch Kodak Ektar F4.5 question

[wuckyboy]

Hey everyone! - So I have somewhat of a silly question but I just want to see what you all think. I have a 7 1/2 inch Kodak Ektar F4.5 serial O-EI 1332 (not a wide field and not a commercial ektar). I currently use a Kodak Master View 8x10 camera. I know that this lens is not supposed to be used with the 8x10 format. But if I'm focused on my subject that is only say 7-15 foot away do you think this lens would cover the 8x10 format at that distance? Every time I mount it on the KMV and focus it to something 7-15 foot away (or even closer) there seems to be pretty good illumination across the entire 8x10 ground glass. Are my eyes deceiving me? I'll probably end up just doing some test exposures to get to the bottom of this, but I'm wondering what your feelings are for using this lens as an 8x10 lens at these closer distances?

Thank you for you thoughts in advance!

[Pere Casals]

One thing is the "good image" circle and another thing is the (larger) illumination circle.

If your subject is at (say) 10 foot but the corners are out of focus then it's not important if the lens performs well in those corners. In that case you may use a lens in a larger format than specs say.

Each manufacturer had their own criterions to say what size had the "good image" circle of a lens, and many lenses illuminate beyond that circle with more or less degradated image quality.

[paulbarden]

I'll probably end up just doing some test exposures to get to the bottom of this, but I'm wondering what your feelings are for using this lens as an 8x10 lens at these closer distances?

You won't really know much about any lens's performance until you put it into use. Will image quality in the corners be less than ideal? Almost certainly. Will there be some vignetting in the corners? Likely. Will any of that be a negative property for what you're doing? Only you can answer that question. Many of us use lenses in ways they were not originally intended to be used, in order to make use of odd behaviors or flaws in the lens.

I have a 5.5" Kodak Anastigmat #31 that I use on a 4x5 camera. It clearly has a circle of illumination that "covers" that format, but image quality degrades quickly in the corners. I use that lens/camera combo specifically to make creative use of these "flaws" in a way that pleases me. For example:

https://live.staticflickr.com/65535/48175780392_b0ff93d87a_c.jpg

[wuckyboy]

Thank you all for the wisdom. I definitely just need to try the lens out, and I for sure will. Guess I’m just wondering if these close distances of say 5-15 feet really do affect the area of the image circle dramatically enough to make the lens an OK performer on 8x10? And then what about even closer at like 3 feet? I’m just so curious because the lens looks beautiful on the GG at some of these closer distances. I was very surprised.

Has anyone out there ever experimented with using a 7 1/2 inch F4.5 Ektar (not a wide field) on 8x10?? What about the 8 1/2 Ektar?

I would say in general that I could live with a bit of blur in the corner or even very slight vignetting if I have a 7.5 inch f4.5 lens that preforms well at environmental portrait distances. Maybe this is all wishful thinking though haha.

[reddesert]

Simple math ahead. This is all basically derived from drawing similar triangles:

If the lens is focal length f, and you extend the bellows by some length e, then the lens is (f+e) away from the film, and generally, if the angle of coverage stays the same, then the circle of coverage is larger by a factor of (f+e)/f, or (1 + e/f). (I'm neglecting that the lens might be less well corrected at very close distances.) It turns out that e/f = m is also the magnification, and m = (f+e)/D where D is the lens to subject distance.

What this means is that if your subject distance is about 10 times the focal length (about 6 feet for a 7.5" lens), then the extension is about 0.1 of the focal length, and your circle of good definition is about 1.1x, so 10% larger. This might be enough to help a 9" or 10" Tessar type cover 8x10, but not enough for a 7.5". On the other hand, depth of field means the corners might be out of focus anyway, so maybe you'll be perfectly happy with the results.

Also, the sheer size of an 8x10 means you might be working closer than 1:10 magnification, depending on what kind of portrait you are doing. That is, at 1:10 you're imaging 80x100" of the subject.

[wuckyboy]

Thank you so much for that! That really spells it out in a clear way. Such a help.

With that I will now try and put the little 7 1/2 Ektar through some tests. I have a feeling that 6 ft and closer is going to yield some surprisingly usable results. We shall see!

[EdSawyer]

If this is the 190mm ektar that came on the Graflex RB Super D, it's a great lens. As mentioned 8x10 might work close up, but it's hard to say. This lens is every bit the same quality as the commercial ektars of the period as well.

[wuckyboy]

I honestly don't know where the lens came from originally. Its in wonderful condition though. I guess it was a wishful thought that it might be my go-to environmental portrait lens for 8x10. Here is a pic of it:194304