G-claron 240 front and rear group for portraits

[koraks]

Sorry if this has been discussed ad nauseam, but a quick Google search didn't yield any specific results.

I've been looking for a usable portrait lens for 8x10 and I'm on a tight budget (bad combination, I know). I realized today that I may have something that could work. I bought this beautiful G-claron 240/9 and thought I'd try the front and rear groups separately and see if that would work. Some quick and dirty measurements yield a 350/13 for the front group and 480/18 for the rear. Obviously slow as all hell, but the perspective is much nicer than the shorter focal length of both groups combined. Inspection of the ground glass image suggests that all options yield perfectly usable images.

Am I correct in supposing this will work (for contact prints and slight enlargements)? What kind of image defects can I expect?

Thanks for sharing your insights!

[Peter De Smidt]

Yes, it should work fine. You may have a bit more chromatic aberration than when using both cells, but I doubt it'll be a problem, especially with BW. Some people use a yellow filter to cut down on some of the aberrations.

I have the same lens. I'll have to give it a try. The biggest issue will be the dark ground glass, especially if you're photographing inside.

[koraks]

Thanks for your confirmation; yes, the GG image is a tad dark, but good light will be required anyway for portraits, so it's going to be an outdoor/daylight and/or powerful artificial light affair anyway. Maybe I'll give it a try later today.

I have no filters at my disposal, but judging by the GG image, CA doesn't seem like a huge issue.

[Peter De Smidt]

See the post by Jean-David Bayer at: https://groups.google.com/forum/#!topic/rec.photo.equipment.large-format/OV8RyhF_Dlg

I expect the G-claron to perform much like a single cell of the Wisner plasmat set.

[koraks]

Peter, thanks for the reading; I did a quick read, but will have to read those posts again to let them sink in.

In the meantime, I just tried a quick portrait to see if the results would be usable. Looks like they are; maybe not so sharp as both groups combined, but more than good enough for contact printing. I think this would enlarge easily up to 2x or maybe 3x without the lens becoming the bottle neck. My haphazard processing and the fact that this is a half second exposure on cheap (and grainy) x-ray film are much more of an issue than any distortion (didn't see any) or coma (maybe a bit, but might as well be motion blur) caused by the lens. The web version, obviously, looks sharp enough, being shrunk to Lilliput size.

http://www.koraks.nl/galleries/8x10_archives/EGRX_810151_01.jpg
G-Claron 240/9 front group only (~350/13), generic green-sensitive x-ray film rated at 100, 1/2 second in available light, no bellows compensation, no filter, tray processed for about 5 minutes in Rodinal 1:67. Epson 4990 scan straight on the platen at 2400dpi, some local contrast adjustments in PS but nothing too vigorous, and some healing of annoying defects (mainly a huge scratch I made during processing).

[Peter De Smidt]

Looks good. Did you move the cell to the back position or leave it on the front?

[Michael Roberts]

This looks great all things considered. I have the same lens but never thought about using it this way, so thanks for this!

Format is 8x10, right? Or 4x5?

[koraks]

Looks good. Did you move the cell to the back position or leave it on the front?
Nah, I just left it on the front. By moving it to the back, do you mean also reversing it back to front? Would that offer any benefits?


Format is 8x10, right? Or 4x5?
Yes, this is 8x10. Focusing requires a lot (*LOT*) of light and I haven't attempted using only the back cell yet for this reason, but in broad daylight, this seems like a very usable setup. Depth of field shot wide open is just right for portraits, I find.

[Peter De Smidt]

Yes, you'd reverse it. If I remember rightly, this was standard practice with convertible lenses, but I don't remember why. Obviously, it works just fine how you did it. I'll see if I have some time today to do some experiments. I'm mainly interested in the 480mm f/18 option, assuming I can see an image on the ground glass.

[koraks]

Hmm, I should read up on reversing the groups when using just one. I knew about this for macro work, but wasn't aware of it in the context of convertibles.

Yeah, you'll get an image alright, but judging critical focus is going to be extremely difficult unless you have a lot of light! This was already a huge issue with the 350/13 option when I was messing about a bit with strobes the other day.

[Kevin Crisp]

There are lots of threads suggesting putting the aperture in front of a single cell (cell inside camera) is advantageous. Ron Wisner used to have posted some comments about lens bench testing that showed some performed better on the front, but it has been a long time since I could check on what he said and I'm going from memory. The conventional wisdom is that convertible lenses when used with both elements do better with the longer cell of a so-called "triple convertible" on the front. Wisner's comment may have pertained to using the shorter cell on the front when both are used.

My personal experience is that I've noticed no difference practically speaking with using a single cell on the front rather than the rear and there can be a big advantage in bellows draw. I've also not noticed a practical difference (with B&L protars) in using a yellow filter. I've found single cell use of Zeiss protars basically useless even at small apertures; the sharpness fall off is just too much for me. B&L ones have always been better for me in that regard.

For you? What you're doing seems to be working fine. I'm going to try it.

[Peter De Smidt]

I was just able to do a quick test. With my 240mm G-claron, the mounting threads for the front and rear cells are not the same, and so moving the front to the back isn't an option. Using just the back cell works, and it produces a dim but managable image on my 8x10 ground glass, using the modeling lights of my Speedotron strobes to provide light for focusing. It really isn't that bad. Holding up Fresnel, a cheap whole page magnifier, to the ground glass does usefully lighten up the corners of the glass. Unfortunately, the rear cell protrudes about 2mm too far back to use as-is with my Sinar shutter. I'll have to make a spacer of some type.