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Photo Forum / Film Photography / Large Format / August 200690mm on 5x7 ?
Anyone using a 90mm on a 5X7 ? > Anyone using a 90mm on a 5X7 ? Sure. You need a high-quality lens to get sharp, even corners. A center filter is very helpful. The equivalent focal length on the 35mm format is around 18mm. > > Anyone using a 90mm on a 5X7 ? > [quoted text clipped - 5 lines] > > The equivalent focal length on the 35mm format is around 18mm. I can imagine falloff is going to be a significant issue. The lens I'm looking at is a 90mm/4.5 Nikkor. Of course there wouldn't be a lot of movement though I seldom need it for landscapes. I was thinking of using it for interiors though that that might be a limitation. According to what I've read the image circle is 235mm with a projection angle of 105 degrees. Can anyone tell me what the image circle would be when focused at 10 feet/3 meeters ? . Can anyone tell me what the image circle would be > when focused at 10 feet/3 meeters ? First you use the principal formula of Optics: 1/F = 1/u + 1/v F is the focal length at infinity (90mm), u is your subject distance (3 meters, or 3000mm - all measurements must be in the same units). Solve for v (lens to film distance). That will give you the effective focal length at 3 meters. Next use: C = 2F'tan (angle/2) (twice the effective focal length times the tangent of half the angle of view). = twice times the v obtained above (=F') times the tangent of (105 degrees/2). That will give you C, the diameter of the circle of coverage. I won't do the math, but it should be easy with a pocket calculator or in MS Excel. Just did the math: The coverage at 3 meters is about 242mm, not much improvement over 233mm at infinity. Cheers, > Just did the math: > > The coverage at 3 meters is about 242mm, not much improvement over > 233mm at infinity. > > Cheers, Thanks Bob. I appreciate the info. > Anyone using a 90mm on a 5X7 ? My Schneider SA 90mm f8 just covers 5x7, but doesn't allow for more than the tiniest movements. The centre filter - Schneider IIIb - is definitely advantageous. The combination is certainly useable, and seems to work well. Your Nikkor should give you a fair bit more movement than that. Peter > > Anyone using a 90mm on a 5X7 ? > [quoted text clipped - 5 lines] > > Peter Thanks Peter. As a side note to this thread, I ended up not getting the Nikkor. For anyone purchaisng on Ebay, you might want to Google "second chance ebay scam". I think I'm going to try to find a decent 105~120 anyway. I'll probably need a little movement capability and even the best 90mm is pretty limited. > My Schneider SA 90mm f8 just covers 5x7, but doesn't allow for > more than the tiniest movements. My Caltar II (Rodenstock) 90mm f/6.8 barely covers a 5x7 at f/22 and infinity.  SignatureMichael Benveniste -- mhb-offer@clearether.com Spam and UCE professionally evaluated for $250. Use this email address only to submit mail for evaluation. > Anyone using a 90mm on a 5X7 ? FWIW, 90mm on 5x7 is about equal to 65mm on 4x5. I have and occasionally use a 65mm Super Angulon (old chrome barrel model) on 4x5 and it works quite well. I think the format is about the limit of coverage for the lens as 5x7 would be for 90mm. You will probably want to use a center filter to even out the exposure, there is a lot of drop off in the corners. For B&W you can get away with it but not for color. I use this lens on a 4x5 Anniversary Speed Graphic. In this camera the minimum limit is such that the back of the lens can touch the ground glass so there is no problem achieving infinity focus even though it is mounted on a standard flat lensboard. However, the GG image is very dim. Since the lens is about at its limit of coverage the lack of movements in this camera is not a problem. I have not tried this lens on my Calumet view camera. I don't know if the bellows will compress enough. I think the recessed lens board would be necessary and I don't want to switch the lens over to it for an experiment. For a 5x7 you will have a similar problem. Both Schneider and Rodenstock have data on the distance required from the back of the lens board to the film plane for infinity focus and also the "back focus" that is the distance from the apex of the rear element to the film at infinity focus. This will allow you to check if the camera will compress enough. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com > > Anyone using a 90mm on a 5X7 ? > > > FWIW, 90mm on 5x7 is about equal to 65mm on 4x5. I have > and occasionally use a 65mm Super Angulon (old chrome barrel > model) on 4x5 and it works quite well. I have one of those too: nice lens, and very small. I have a newer f5.6 one as well, and it has more coverage, but it isn't any sharper than the older lens, and a lot bigger. > I think the format is about the limit of coverage for the lens as 5x7 > would be for 90mm. You will probably want to use a center filter > to even out the exposure, there is a lot of drop off in the corners. > For B&W you can get away with it but not for color. I'll second that - w.r.t. to both these lens/format combinations. Sometimes leaving the centre filter off can be a useful effect though, especially in combination with some back swing. > I use this lens on a 4x5 Anniversary Speed Graphic. In > this camera the minimum limit is such that the back of the [quoted text clipped - 7 lines] > board would be necessary and I don't want to switch the lens > over to it for an experiment. I have a 6x9 Century Graphic and it makes a lovely wide-angle camera because of those oh-so-compressible bellows. Even takes a 38mm SA XL in a flat board, but you have to unscrew the rear group, fit the lensboard and then screw the rear cell on again from behind, which is fiddly to say the least! I would expect you probably would need a recessed lensboard to use your 65mm on the 4x5 Calumet view. I need a slightly recessed board to use it on my Arca Swiss (s, is z, zz, whatever the plural of "Swiss" is...) I can then even use it with the standard bellows, but the bellows is so compressed then that I do have to switch to the bag bellows if I want to use any movements. > For a 5x7 you will have a similar problem. Both Schneider > and Rodenstock have data on the distance required from the > back of the lens board to the film plane for infinity focus > and also the "back focus" that is the distance from the apex > of the rear element to the film at infinity focus. This will > allow you to check if the camera will compress enough. The flange distance for the Schneider 90mm f8 is 99mm, so you have a bit less 'bellows compression' to deal with than you might expect (actual FL is just under 91mm). 90mm on my Arca 5x7 is just fine with the standard bellows and a flat lensboard. Bag bellows would allow more movement, but as the coverage on doesn't allow much on 5x7 anyway, the fact that I don't have a bag bellows for this format doesn't bother me much. Peter |
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