jim_carney1 Posted August 9, 2003 Share Posted August 9, 2003 I' contemplating making the move to medium format after centuries of 35mm shooting. My dilem is which lenses should I get to go along with a Mamiya 645Pro-TL? Which focal lenght would make the best portrait lens? What would be an equivalant to a 28mm on a 35mm camera? Link to comment Share on other sites More sharing options...
ky2 Posted August 9, 2003 Share Posted August 9, 2003 45mm. Link to comment Share on other sites More sharing options...
jimvanson Posted August 9, 2003 Share Posted August 9, 2003 If you can see the complete viewing screen on the contemplated mamiya (I couldn't) go for it...but renting one to try first may be a REALLY good idea. Fantastic deals are to be had right now in 645, utterly fantastic! (unless of coarse you already own 10,000 worth of kit that is now worth $3500).<p>A 28mm in 35mm is roughly a 55 in 645, as a 50 in 35mm is a 30 in 645. Link to comment Share on other sites More sharing options...
jimvanson Posted August 9, 2003 Share Posted August 9, 2003 Yarons right!!! I went the wrong way...at least I didn't when I bought a 645n Pentax...great camera (whose 45mm lens equals a view of a 28 lens on a 35mm format). Sorry Link to comment Share on other sites More sharing options...
leonard_evens Posted August 9, 2003 Share Posted August 9, 2003 It is a bit tricky comparing focal lengths for 35 mm and 645 because the format aspect ratios are different. 35 mm format is 24 x 36 mm (ratio 2:3) and 645 is close to 45 x 56 mm (close to ratio 4:5). You have to pick a dimension to get a focal length ratio and then multiply focal lengths by that. If you pick the short dimension, the ratio is 45/24 = 1.875 and if you mulitply 28 by that you get 52.5 mm. If you pick the long dimension, the ratio is 56/36 = 1.56 and you get 43.6 mm. If you pick the diagnonal, the ratio is 71.8/43.3 = 1.66, and you get 46.5 mm. So 45 mm is pretty close, but you have to realize that a 645 picture in landscape mode, while horizontally it will have close to the same angle of view, will also show more vertically. This may be a bit disconcerting until you get used to it. Link to comment Share on other sites More sharing options...
joseph_walsh2 Posted August 9, 2003 Share Posted August 9, 2003 For a rough but pretty good estimate, take any 35mm FL, add 50% of it and that's the 645 equiv. E.g., 50mm normal = 75mm normal in 645 (50+25); 40mm=60mm Link to comment Share on other sites More sharing options...
robert_byrd1 Posted August 9, 2003 Share Posted August 9, 2003 Jim, do you mean fantastic deals on used 645s or on new ones? Link to comment Share on other sites More sharing options...
jimvanson Posted August 9, 2003 Share Posted August 9, 2003 Both...new eg Bronica's 645 Rangefinder kit @ $1150o r Mamiya's 645e @ $700! or used RB for less then $600 complete, p645's less then $500. It's a buyers dream. Link to comment Share on other sites More sharing options...
FranzWeber Posted August 10, 2003 Share Posted August 10, 2003 For portraits you can use 150mm ~ 93mm on 35mm camera. Link to comment Share on other sites More sharing options...
mario_visperas Posted August 11, 2003 Share Posted August 11, 2003 The angle of view is based on the diagonal of the film. The diagonal of the 35mm film is (based on 24mm x 36mm dimension) ... diagonal(35mm) = sqrt ( 24^2 + 36^2) = 43.2666 mm The angle of view is ... _ /| ^ / | | / | | / | ----| diagonal of film \ F | \ | | \ | v \| _ angle of view = 2 * ArcTan [ (diagonal / 2) / Focal Length] Therefore for 28mm Focal length, ... angle of view (35mm) = 2 * ArcTan [ (43.2666 / 2) / 28] = 75 degrees ************* For an equivalent lens for 645 film, ... 645 film dimensions are 60mm X 45mm (or 6cm x 4.5cm) Therefore, the diagonal is,... diagonal(645) = sqrt ( 60^2 + 45^2) = 75 mm angle of view (645) = 2 * ArcTan [ (75 / 2) / F] For the 2 lenses of different format to be equivalent, they have to have the same angle of view. Therefore, Focal length (F) of 75 degrees angle is, ... F = (diagonal / 2) / [ tan(angle / 2) ] = ( 75 / 2) / [ tan( 75 / 2) ] F = 48.8mm Choose a Focal length closest to 48.8mm. Manufacturers do not produce exactly 48.8mm. Hope this helps. mario Link to comment Share on other sites More sharing options...
mario_visperas Posted August 11, 2003 Share Posted August 11, 2003 Darn, my text drawing is messed up after posting. Here it is again ... The angle of view is based on the diagonal of the film. The diagonal of the 35mm film is (based on 24mm x 36mm dimension) ... diagonal(35mm) = sqrt ( 24^2 + 36^2) = 43.2666 mm The angle of view is ... _ /| ^ / | | / | | / | ----| diagonal of film \ F | \ | | \ | v \| _ angle of view = 2 * ArcTan [ (diagonal / 2) / Focal Length] Therefore for 28mm Focal length, ... angle of view (35mm) = 2 * ArcTan [ (43.2666 / 2) / 28] = 75 degrees ************* For an equivalent lens for 645 film, ... 645 film dimensions are 60mm X 45mm (or 6cm x 4.5cm) Therefore, the diagonal is,... diagonal(645) = sqrt ( 60^2 + 45^2) = 75 mm angle of view (645) = 2 * ArcTan [ (75 / 2) / F] For the 2 lenses of different format to be equivalent, they have to have the same angle of view. Therefore, Focal length (F) of 75 degrees angle is, ... F = (diagonal / 2) / [ tan(angle / 2) ] = ( 75 / 2) / [ tan( 75 / 2) ] F = 48.8mm Choose a Focal length closest to 48.8mm. Manufacturers do not produce exactly 48.8mm Hope this helps. mario Link to comment Share on other sites More sharing options...
q.g._de_bakker Posted August 11, 2003 Share Posted August 11, 2003 Mario, You wrote: "For the 2 lenses of different format to be equivalent, they have to have the same angle of view." Horizontal? Or diagonal? ;-) Link to comment Share on other sites More sharing options...
richard_cochran Posted August 11, 2003 Share Posted August 11, 2003 <cite>Horizontal? Or diagonal? </cite><p>Vertical. At least sometimes.<p>Do you crop the edges off a 35mm frame to get 8x10 or do youcrop the top and bottom off a 645 to get a 4x6? Is a squarea cropped rectangle or is a rectangle a cropped square?What's the sound of one hand clapping? Link to comment Share on other sites More sharing options...
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