G Claron & other process lenses

[Geoffrey Poulton]

Hi Kevin

A black light sounds like a sky hook here in the UK - sort of Alice in Wonderland!! I'll see what I can locate in the UK, I think I've read your past post on that particuarly set up, but you didn't go as far as the pirate ships and fondue!

[Geoffrey Poulton]

The process lenses are designed for minimal aberrations (chromatic etc) when they are focused at shorter distances. The only thing that prevents them from focusing to infinity is your bellows length. Although their aberrations are less at the distance they were optimized for, many still have excellent performance at infinity. Similarly a lens which minimizes aberrations at infinity can still have excellent performance at distances less than infinity. For most lenses aberrations decrease as the lens is stopped down from wide open until diffraction becomes dominant.

Thanks Jeff, that's worth bearing in mind, someone on another post said that because a lens is computated for close work, it does not follow that it is poor at infinity. Thanks for this info, I'm going to remember it!

[Drew Wiley]

I have several Apo Nikkor barrel repro lenses that are simultaneously sharper at both infinity and closeup by f/111 than any official view camera lenses I own (and that includes late Nikkor M's, G-Clarons, Fuji A's). They've even sharper and better apo corrected than any offical apo enlarging lenses I own. And of course, certain Apo Ronars were famous for both closeup and infinity use, though these had less generous image circles.

[kleinbatavia]

Nothing scientific, but I've recently completed testing of a whole range of process lenses, including g-clarons. All I can say is that when stopped down, g-clarons yield incredible detail at pretty much any focal distance. You're going to be hard-pressed to find a lens that resolves more detail. Colour and contrast are good too. I can highly recommend them.

[Jim Andrada]

My second lens (bought new around 1972) for my 5 X 7 Kardan Bi was a 305 mm Repro Claron. Absolutely love it to this day. For everything near and far.

https://www.flickr.com/photos/895141...n/photostream/

https://www.flickr.com/photos/895141...n/photostream/

https://www.flickr.com/photos/895141...n/photostream/

[Geoffrey Poulton]

Hi Drew
Do you mean the Nikkor M's, G-Clarons & Fuji A's are even sharper and better apo corrected than any offical apo enlarging lenses you own?

[Geoffrey Poulton]

Thanks Jim

I've come across two of these picture before when I've been looking around. I think you may have had your money's worth from your 1972 purchase of the 305mm by now - whatever you paid for it! The shutter for my Repro Clarin is being cla'd and I'm really looking forward to using it. It's hard to imagine a lens being much smaller than this as 210mm.

[ic-racer]

G Claron lenses are detailed as being capable of infinity focus when stopped down to f22.

When taking landscape images I almost invariably use forward tilt and a degree of hyperfocal distance focusing.

When the G Claron lenses (etc) are described as capable of infinity focus at f22, does this refer to the lens already having been focused out to infinity or take into account a degree of focusing employing hyperfocal distance?

Knowing the official explanation of this is probably more helpful than trying to work it out by taking a number of shots to see the effect, which is quite expensive where 5x4 film is concerned and which may not lead to a better understanding.

Extra stopping down beyond a certain point is not usually a good idea either.
I'd be grateful if anyone has any information on this or even the definitive answer.

Thanks Geoff

The question for process lenses at infinity is "will the entire horizon be in focus." That is the working definition of "flatness of field" for non-process lenses. From the flat film's frame of reference it is as if the horizon is curved. Your best bet is to use the standard "defocus/diffraction" focus method of Hansma to get the entire curved image in focus. Tilt and hyperfocal focusing are not the best answers to the problem at hand. Downward front tilt makes it worse; with a process lens, the edges of the scene focus too close to the camera making the grass is in focus but the horizon is blurry at the edges before you apply any tilt. Hyperfocal focusing is something out of a handbook on small format hand-held photography and usually of no benefit to large format photography on a tripod.

[Drew Wiley]

Geoffrey - My Apo Nikkors (appropriately used per specific focal length) are on the ENLARGER both sharper and more "apo" than any of my official apo enlarging
lenses. On the view camera, they are equally superior to any of my official view camera lenses, optically at least. (Add a shutter, and that might be offset by
shutter vibration itself if one is forced to go to a big no.3 versus no.1, for example). But a modern plastmat G-Claron will be merely decent for enlarging - better than many older enlarging lenses, but nothing like an Apo Rodagon N. And a Nikkor M would probably be completely inappropriate on an enlarger, though its a
remarkable lens series for general shooting, provided you don't need huge image circles.

[kleinbatavia]

Quite happy with my graphic kowa and computar lenses. Also use an apo ronar 360mm, but pending develiping some sheets shot with an alternative it may have to go. Still prefer my g-clarons... They somehow enable me to create images I can't make with other lenses. Particularly in b/w.