It is possible to calculate geometric equivalents between 35mm and LF lenses but the numbers may not end up being a good guide in transferring one's "vision" between formats.
More than thirty years ago I shot 35mm with wide and wider lenses. I had one of the first Spiratone 18mm lenses on my Pentax and knew for sure that I would need an ultra-wide lens for my new Nagaoka 8x10. All I could afford at the time was a Fujinon W 300 f5.6 so the LF wide never got purchased. And I ended up not missing it. Why?
I realised that I was using the Spiratone 18mm lens for DEEP landscapes, connecting foreground and background and keeping everything sharp. The WIDE aspect was a side effect that, often as not, condemned the pictures to being 85% periphery and only 15% middle.
The 300mm normal lens on the 8x10, combined with the powers of the Scheimpflug condition, delivered that DEEP all-in-focus landscape without battling with the challenging "emptiness" that often infects the ultra-wide view. It would have been a mistake for me just believe the numbers and translate my 18mm Spiratone lens into a 115mm Grandagon!
Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.
Oh, let's really complicate things and point out that as you progress in photography, your vision may change. I started out with the standard 150-210-300 set in 4x5 and ended up selling them all and going to 135-180-270. I'd suggest a "normal" focal length like 150mm or 135mm and see how it feels before acquiring other lenses.
That's because if your subject matter is open landscapes like in the West, a longer 180mm-210mm may be "normal" while the more constricted landscapes like I have in the East may call for a shorter 135mm. If I average 135mm and 210mm, I get 345mm/2 = very close to 150mm, which may or may not suit you.
Since the two formats have different aspect ratios, there are no *direct* AOV equivalents. You get near-direct equivalents with 6x9 format, but not 4x5, or most others.
When most people speak of equivalents, they are speaking of diagonal AOV equivalents. These give you a good general idea, but will leave you disappointed if you need an exact equivalent for some reason.
I prefer to look at horizontal and vertical AOVs. Each one of these has a different factor to find an equivalent. The factor for horizontals is approximately 3.6. The factor for verticals is something that I forgot, and the online AOV calculator I like is not working right now.
With a horizontal AOV equivalent, the horizontal AOV will be the same as the 35mm equivalent, but the vertical AOV will be wider than the 35mm lens.
With a vertical AOV equivalent, the vertical AOV will be the same as the 35mm equivalent, but the horizontal AOV will be narrower than the 35mm lens.
Depth of field will always be greater for a given AOV with a smaller format film, since longer focal lengths are needed to achieve the same AOV.
Last edited by 2F/2F; 01-20-2009 at 07:03 PM. Click to view previous post history.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
- Rob Tyner (1944 - 1991)
In reality I tend to think of both dimensions as I'm regularly shooting with 5x4 usually with a 135mm or 90mm lens plus a 6x6 TLR with an 80mm, and to complicate things more also a 6x17 & 75mm Super Angulon. However it's easier in practice than it sounds, you rapidly get an instinct for framing & composing each format/lens and you don't think of what's equivalent to what while shooting, I frame each image intending to print full frame.
Here's a useful link for calculating angle of view (horizontal, vertical, and diagonal): http://www.imaginatorium.org/stuff/angle.htm
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What Walter said.
Changing from 35mm to 8x10 is sorta like changing from trumpet to sax. What you know about music (how to read, tonality, rhythm, etc.) carries over. However, what you know about how to physically play the trumpet is of little value in physically playing the sax.
What you know about photographing with 35mm cameras is of limited use in using a view camera. This includes lens choice. While you can figure out and buy an "equivalent" lens for 8x10 from your 35mm days, you will likely not use it the same way, if at all.
Don't confuse belief with the truth. Few who are in the process of making the transition believe the experiences of people who have made the transition before them. But that doesn't mean they aren't telling you the truth.