medium format vs large format lenses

**Robert A. Zeichner** · 9-Aug-2001, 21:02

I strongly urge you to read my article in the Nov/Dec 1996 issue of ViewCamera. The test set up I describe is specifically designed to take contrast into account. It actually makes use of perceived contrast to help in determining whether or not your camera passes the test! It is designed to test gg alignment under the most unforgiving conditions. The actual (and optimum) performance of most view camera lenses are usually obtained when stopped down. The depth of field needed for most photographs is exactly what you don't want when testing ground glass alignment. Beer bottles, water skis and newspaper print don't begin to do the job of a good test target.

**Bill Glickman** · 9-Aug-2001, 21:07

I agree with Chris above.... I have run these tests also, to check gg and film alignment... if take a paper with small print, (you need to experiment with the size based on the fl lens you are using) and have 60 lines of print... like, 11111 on the first line, 222222 on the second line etc. Then you take that paper and put it on a slant board, so that with the lens wide open, you only have one line in focus and all other lines out of focus ( you need to experiment with the slant angle) Note which line is in focus...take a shot wide open and see if the same line is in focus on the film. This is good indication of gg / film alignment, not as good as lasers, but a good first test...

**Walter Glover** · 10-Aug-2001, 07:59

Mike:

A low contrast Nikkor??? rare bird. The fact that the Nikon 90 is not as sharp as the Rodenstock 180mm indicates to me that there is still case answerable for film plane / GG plane alignment.

The error does not have to be very great for it to have a devastating effect on the image quality so what I suggest is that you remove the Ground Glass frame as you would to place a Graflok holder in place and then check the metal surface surrounding the ground glass for burrs, dirt hair etc. and then check the surface upon which it seats. Maybe there is a ridge of light trap material or some other particle.

While you're at it, check your film holders.

Walter

**Charlie Stracl** · 10-Aug-2001, 15:02

There is a chance you have bad lenses. They don't all come out perfect! Take Bob Solomon up on his offer to check your lens out.

(Having 2 bad lenses, each from a different supplier seems unlikely, but it is possible.)

Charlie

**Julio Fernandez** · 11-Aug-2001, 02:04

Mike: Forget about all the dissertations about lenses! With MF the film plane is determined from birth, and the only deviation will be the result of the paper and film buckling. With LF cameras the film plane position is determined by the camera construction, the way the GG is installed and by the film holders. Additionally, one hopes that the GG is also at the same position. One photographer that does workshops always starts its students by calibrating cameras, which invariably are off calibration. Holders also can vary significantly. I have one Linhof holder that has perfectly flat septums on both sides, even though there is a slight difference in the film plane from one side to the other. I have measured many other holders from several other brands, none measure up to this one Linhof holder. Friends, when talking about film sharpness it's time to give up 35mm and MF thinking habits and realize that the mechanics are totally different. Forget about differences in optics for the start and start with the basics. The needed measurements require a depth micrometer and a perforated (for the micrometer probe) "flat" aluminum plate. Not much to it except for patience and attention to detail. Re-check your work and do statistics to avoid errors. With a little thought you can figure out what has to be done. Check your GG, then your holders and don't be surprised at the discrepancies. Finally, do not skimp on holders. The cheapest plastic can ruin the images from your space age glass. Remember when saving $20 on holders how much you paid for the glass and how much it cost you to get there. I can think of no photo expense that is cheaper than film holders. With Linhof later model technikas the GG position can be adjusted to within 0.001" by turning tiny screws. If you are lucky, your camera also provides for adjustments. I personally would not buy any LF camera that can't be adjusted.

**Paul Schilliger** · 11-Aug-2001, 04:59

Mike, sorry for this basic question, but I have seen this happen a few times: Is your tripod really strong enough to hold your view camera steady as a rock and absorb the shutter shake and the v ibrations due to wind and cable release operation?

But even if it's the case, your Mamiya lenses will beat the LF lenses by far. Ch eck Chris Perez lens test pages (http://www.hevanet.com/cperez). Some Mamiya lenses produce as much as 95 l/mm w hen an excellent LF lens at it's best opening hardly passes 67l/mm. Film flatness is also an issue with L F. Check also what apertures produce the best results. Usually 16-22. At f32, a LF lens is considerably softe ned.