80mm for 6x7?

Hi,

Having Mamiya RBproS for two months for now, times comes for print making. Now, I have 80mm lenses (Schneider Componon-S, Rodenstock Rodagon, and Meopta Anaret). I also have colour head for my Meopta Magnifax 4 enlarger, I use that head for multicontrast papers. I also have mixing chambers for 24x35mm, 6x6cm, 6x7cm and 6x9cm negatives. And also apropriate condenzor lenses for b/w head for graded papers. But I don't have 90mm enlarger lens. So, question is:

Will I have any problems (sharpness problems, distorzion problems, light falls or magnification problems) if I use 6x7cm mixing chamber, or apropriate condenzor lenses, with 80mm lens for 6x7cm negatives? Or, asked other way, must I buy 90mm enlarger lens for 6x7cm negatives?

Note: For example Rodenstock even don't have 90mm lens in Rodagon line. They in theire catalogue state that theire Rodagon 80mm is for 6x7cm negative size. On the other hand in ApoRodagon line they have 90mm lens, and Schneider also have 90mm Componon-S lens.

So, again, 80mm enlarger lens for 6x7cm negative. OK or not?

Thank you and regards.

That's what I use for 6x7 negs! Works great!

The 80mm should not be a problem. Actually, a 105mm is what was recommended to me for my 6x7 negs and what I use. I don't have an 80mm for 6x6 negs, but use the 105 and it works out well. The 80 will allow larger prints at a lower head height; using the 105 for 6x6 just means cranking the head up higher than I would for an 80mm.

I have looked into this a while ago, 90mm or higher is recommended for 6x7, but most people seem have no problems printing with an 80mm lens.
From what I have read coverage and the use of the recommended lens becomes critical when printing large.
With a bit of patience you can find a 100mm (Componon-S) or 105mm (Rodagon) between $40 and $60 on ebay.

Good luck!
Imke

I personally use a 105mm - but hey! if your 80mm covers, why not?

Depends upon the design of the lens. My El Nikkor says the 80 mm lens is good for 6x7. I think any 6 element lens probably has coverage for 6x7, but a 3 element lens probably doesn't.

Try the 80 mm and look for vignetting (dark edges) on full frame enlargements, or do this test:

Leave the 6x7 carrier empty (no negative).
Enlarge the carrier edges to less than the borders on your easel (you want the edges of the carrier to show up within the easel opening).
Focus the edge of the carriers.
Expose a sheet of paper for a light gray tone with the lens wide open.
Develop.

If the edges are darker, you have vignetting. If the tone is consistent, you don't have vignetting.