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03-10-2010, 08:56 PM   #31
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FF allows for fast and wide; APS-C is a better choice in the telephoto range.

The FA*24 is a fast (ultra)wide on FF but a plain medium wide on APS-C and there is no fast 16mm prime.
The FA31 is a fast wide on FF, but a plain normal on APS-C and the DA21 is slow (but small).
The FA43 is a fast normal on FF, but a weird short tele on APS-C. We have no fast 28s.
The FA24-90 is a fast-ish standard zoom on FF, but a 35-135 on APS-C. The DA 17-70 and 16-45 are similar but both are larger. In the wide FLs, APS-C lenses aren't actually smaller unless they're slower (which is not format specific).

APS-C is excellent for sharp telephotos, and FF is an easier way out for wide-normal vs making a bunch of new F1.x DA primes. I think a Pentax FF would be about as expensive and/or easy to develop as 16, 21, 24, and 35mm lenses that are faster than F2.

03-10-2010, 09:37 PM   #32
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QuoteOriginally posted by photogerald Quote
There will be some loss with cropping, as lens quality will come into play. Of course the loss will be less with more $$$ glass.
When you have a lot of real estate (frame size, film or digital) you can afford to trim away the excess. One reason fashion etc photographers use MF is because lots of area can be cropped while still leaving a large image to work with. When I shoot MF film I can be less than perfect with composition, level horizons etc and still have enough usable negative for LARGE prints.

The diagonal of a frame is traditionally used to compute the 'normal' focal length. Note these diagonals vs the most common 'normal' lenses for these formats:

format - diagonal - 'normal'
-------- ----------- ------------
6x9cm - 101mm - 100-105
6x6cm - 92mm - 80-85mm
645cm - 70mm - 65-70mm
135/FF - 43mm - 50-55mm

On MF, the 'normals' are near or slightly wider than the diagonals. With 35mm full-frame, the 'normal' lens is actually a short tele. (APS-C has no standard 'normal' because the standard kit lens is a zoom centered around 36mm, a long-normal focal length.) A theory is widely held (citation needed) that 135/FF has 50-55mm 'normals' because users pre-crop -- that serious 35mm photographers, having less real estate (frame area) to play with, shoot tighter, ending with an image aspect that MF photographers would often crop to achieve.

Maybe I learned that from my dad. He shot 6x6cm, printed some square shots, but mostly printed 4x5", 5x7", 6x9", 8x10". The square negative was just fodder for the rectangular enlarging frame.

Note that the new 645D has a frame size of 33x44mm, giving a diagonal of 55mm, and their first lens is a 55mm. That's equivalent to 43mm on 135/FF, a "wide normal" by 135/FF standards. Of course, it's not like Pentax has no experience making 55mm lenses... But IMHO it shows that the 645D market will be MF photographers with a habit of cropping.

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