I am going to be using a Toyo 4x5 camera with a 6x7 roll film back and I'm wondering how to figure out the approximate 35mm lens equivalents so I can estimate the coverage angles. I am assuming that the usual 4x5 lens calculations with the smaller 6x7 film size will be off and I will need longer lens. I'm looking for the equivalent of a 28mm wide angle in 35mm. In 4x5 format that would be about a 90mm lens, but I'm assuming that I will need something longer to get the same coverage in the 6x7 film format.

-- Keith A. Dunlop (kdun@gte.net), December 07, 2000

Answers

Keith,

You will need a wider focal length, not longer. To determine the proper 6x7 focal length, simply double your favorite 35mm lens. So, if you like a 28mm in your 35 system, you'll need close to a 56mm when using the 6x7 back on your Toyo 4x5. Schneider makes a 58mm and Rodenstock a 55mm.

-- Ross Martin (ross@rossmartinimages.com), December 07, 2000.

Keith, here's a site with a lens table. http://www.geocities.com/SoHo/Nook/4792/copyright_texts/LargeLens.html Dan

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-- Dan Carey (danimal_57@yahoo.com), December 07, 2000.

Keith, the nearest easily available lens that is closest to 28mm in 35mm format is the 55mm Rodenstock. Its' width angle is 64.2°, height is 54°, and diagonal is 77.9°. It actually equals a 29mm lens on my chart. If you're dead set on equaling a 28mm you'll need the 53mm Biogon.

-- Garrett Adams (gadams@jps.net), December 07, 2000.

Thank you all for the responses. I did some lens cost research after receiving your responses, and buying a 55mm large format lens is going to be extremely cost prohibitive. The original idea of using the 6x7 roll film back is so I don't have to get any new darkroom stuff while I try out large format. I think I'll be getting a 105mm Nikkor and I'll settle for normal perspective with 6x7, with an eye towards using it for wide angle if I start shooting in 4x5.

-- Keith (kdun@gte.net), December 07, 2000.

Can you print 6x9? If so, go w/a 6x9 back and a 65mm Super Angulon - this is the same as a 28mm field of view in the 35mm format. You can find the 65mm SA used from $350.00 and up.

-- sheldon hambrick (sheldon_hambrick@hotmail.com), December 08, 2000.

I'm not aware of any 105 mm that will cover 4 x 5. As for 65 mm lenses, the Horseman 65 mm f7 Super is an excellent lens for 6 cm x 9 cm format. There's a multicoated one (very rare) up for auction right now on EBAY. I think the reserve is about $600.00, which is not cheap, but for a multicoated 65 mm f7 for 6 x 9 that's as small and nice as the Horseman, it's something to consider.

-- Howard Slavitt (info@naturelandscape.com), December 10, 2000.