Beginner's questions about roll film backsgreenspun.com : LUSENET : Large format photography : One Thread
I have been considering getting a 6X7 roll film back for my 4X5. My purpose is to reduce my film costs for some shots shots and for practice, and still have the 4X5 option for the hopefully dynamite shots. There are a couple of basic questions I've been wondering about.
Reviewing resolution charts for LF lens opposed to lenses intended for use on a 6X9 view camera or many of the MF lenses, it would seem that the resolving power of LF lenses is appropriately designed for the 4X5 image size. With the roll film back, can I still expect to get respectable sharpness, say a good 16X20 enlargement as a reference point, or an image quality comparable to a decent MF 6X7 camera. Or is the 6x7 image too much of a compramise for typical LF lens?
A little more basic would be how to determine the image size on the ground glass. I have unmarked ground glass. I've thought of using a sharpy pen to outline the 6X7 image on the glass. Are there better ways without buying new ground glass?
Thanks for the help.
-- Roger Rouch (email@example.com), November 21, 1999
The differences you worry about look much bigger on paper than they do in real life. When I use it correctly (not often enough!) my 2x3 Graphic with an old Nikkor 105M lens easily equals the quality of my Hasselblads.
With good technique, you should get pretty good quality; however...the real problem here still awaits you; the difference between 4x5 and medium format is huge and not just for reasons of resolution.
Take a modern print made from a high quality medium format camera, compare it to a print of the same size made from 4x5 in the forties. Sure, the modern print might have greater resolution, but that's not even the biggest difference! Look at the tones!
There's much more to large format than resolution...there are no equivalents at different print sizes...just different styles that suit different people.
-- Brian Yarvin (firstname.lastname@example.org), November 21, 1999.
I use a Horseman 6X9 roll film back on my Wista SP with terrific results. At 16X20 print size the difference in sharpness between that produced with a 6X9 vs. a 4X5 transparency is not significant, in my opinion. I use a variety of Nikkor and Schneider lenses. You've already mentioned the economic benefit of shooting roll film in terms of film cost...it's also alot easier to bracket your exposures when using roll film vs sheet film. A disadvantage of using a 6X7 roll film back comes when doing wide angle work. To get a wide angle view with this setup requires a very short focal length lens which could create other problems depending on what camera you have such as the need for wide angle bellows and/or recessed lens boards. For example, a 90 on a 4X5 gives a view equivalent to a 24 on a 35mm camera. When I put a 6X9 roll film back on that view equivalent changes from roughly a 24 to a ~35mm lens.
In regards to determining image size on the ground glass I made a mask that I fit over the ground glass when composing the image. I cut a piece of matboard to the dimensions of the ground glass then cut a 6X9 window in the exact center of the matboard. The only problem I've encountered using this setup is remembering to throw the mask in my backpack before hitting the trail.
-- Mark Windom (email@example.com), November 21, 1999.