Jack_Flesher Posted September 27, 2007 Share #21 Posted September 27, 2007 Advertisement (gone after registration) Here is the issue as I see it: 1) If you do the math, the crop should equal the perspective new net effective focal length. 2) Using a shorter lens on the cropped sensor for the same FoV as full-frame, will yield a different net DoF than you would have had on full-frame when using the same aperture on the two different focals. 3) However for some reason my "most used focals" from film M's are still my "most used focals" on the M8 when they in fact should be roughly the one step shorter focals. I cannot explain 3 in light of 1, but it is how it seems to work out for me in actual practice, and I know I'm not alone in this. My theory is it has to do with the viewfinder in the M8 itself, coupled with the DoF difference in 2, both working together and forcing me to "see" my compositions a little more tightly composed than before, but with similar DoF look. I don't have any empirical evidence to back that up however, so it's just my guess... Could just as easily be I've changed my style over the past few years to a tighter look Cheers, Link to post Share on other sites More sharing options...
Advertisement Posted September 27, 2007 Posted September 27, 2007 Hi Jack_Flesher, Take a look here M8: Extension (crop) factor vs Perspective. I'm sure you'll find what you were looking for!
Guest tummydoc Posted September 27, 2007 Share #22 Posted September 27, 2007 Here is the issue as I see it: 1) If you do the math, the crop should equal the perspective new net effective focal length. Careful now, lest you be spanked for daring to suggest that a photographer believe in such heretical hocus-pocus as mathematics 2) Using a shorter lens on the cropped sensor for the same FoV as full-frame, will yield a different net DoF than you would have had on full-frame when using the same aperture on the two different focals. 3) However for some reason my "most used focals" from film M's are still my "most used focals" on the M8 when they in fact should be roughly the one step shorter focals. I cannot explain 3 in light of 1, but it is how it seems to work out for me in actual practice, and I know I'm not alone in this. My theory is it has to do with the viewfinder in the M8 itself, coupled with the DoF difference in 2, both working together and forcing me to "see" my compositions a little more tightly composed than before, but with similar DoF look. I don't have any empirical evidence to back that up however, so it's just my guess... Could just as easily be I've changed my style over the past few years to a tighter look Cheers, You've got it spot-on. Empirically there is strong evidence that people tend to favour the lens whose frame occupies the largest comfortably-seen frameline in the finder. 50mm on M3, 35mm on most others. Leica know this, which is why they released a new 28mm concurrent with the M8. There is however, a more distinct difference in the overall characteristics between a 28 and a 35 than between 35 and 50, so the 0.58-magnification finders weren't enough persuasion, without a crop factor, to oust the 35 from favour. Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted September 27, 2007 Share #23 Posted September 27, 2007 Photographers do math. What are you nuts. i just know how to add and subtract anything else i hire someone. ROTFLMAO Link to post Share on other sites More sharing options...
pemayeux Posted September 27, 2007 Share #24 Posted September 27, 2007 I have experienced the same thing as Jack - my favorite lenses on my film Ms are also my favorite on the M8, the most used being the 35mm. Link to post Share on other sites More sharing options...
Philippe D. Posted September 27, 2007 Share #25 Posted September 27, 2007 Hi, I would like to try to make it easy, but with my broken English, it could be hard. A lens have a certain Image Circle, the optical characteristics (depth of field, angle of view) are fixed, they don't change. What change with the crop is the Image Size. So take a picture on paper, which has been taken with a 21mm lens, then cut this picture with a scissors 1/3 smaller. You'll get a smaller picture which looks like taken with a 28mm lens. That's, in my mind, the crop factor. Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted September 27, 2007 Share #26 Posted September 27, 2007 Plain english here . Stick a camera on a tripod take a FF camera and stick a 28mm lens on it take a image than replace it with a M8 and a 28mm lens and not move a inch than the prespective does not change at all it still is a 28mm lens perspective. The only difference is the M8 image is cropped to a 35mm image size. Now on the M8 to equally the FF image of 28mm you would have to move back than the prespective would change along with DOF Link to post Share on other sites More sharing options...
sparkie Posted September 27, 2007 Author Share #27 Posted September 27, 2007 Advertisement (gone after registration) Hi, I would like to try to make it easy, but with my broken English, it could be hard. A lens have a certain Image Circle, the optical characteristics (depth of field, angle of view) are fixed, they don't change. What change with the crop is the Image Size. So take a picture on paper, which has been taken with a 21mm lens, then cut this picture with a scissors 1/3 smaller. You'll get a smaller picture which looks like taken with a 28mm lens. That's, in my mind, the crop factor. Yes. I agree 100%. Thanks for your well explained reply Link to post Share on other sites More sharing options...
sparkie Posted September 27, 2007 Author Share #28 Posted September 27, 2007 Plain english here . Stick a camera on a tripod take a FF camera and stick a 28mm lens on it take a image than replace it with a M8 and a 28mm lens and not move a inch than the prespective does not change at all it still is a 28mm lens perspective. The only difference is the M8 image is cropped to a 35mm image size. Now on the M8 to equally the FF image of 28mm you would have to move back than the prespective would change along with DOF Excellent explaination. So its a double-edged sword. 1. If you move 3 or X steps back to fit everything in on a cropped M8 then your perspective changes (slightly - depending if you have any up close subjects) 2. If you buy a wider lens it costs you thousands of $$$ and also a wider lens angle perspective and greater distortion. but this may be to your liking and shooting style I like 1. 'cos.. a. its cheaper and b. i have faster longer focal lengths. the wider lenses only max out to f2.8 (for the 21 & 24) and f2.0 for the 28. I have a 35/1.4 and I can step back. for my slower lenses like the 28/2.8 I just crank up the ISO. though given not every situation will be suitable. I figure a 28 or 24 f1.4 is in the works? Link to post Share on other sites More sharing options...
Jack_Flesher Posted September 27, 2007 Share #29 Posted September 27, 2007 2. If you buy a wider lens it costs you thousands of $$$ and also a wider lens angle perspective and greater distortion. but this may be to your liking and shooting style AND less DoF at the same aperture compared to the longer lens with full-frame... Link to post Share on other sites More sharing options...
luigi bertolotti Posted September 27, 2007 Share #30 Posted September 27, 2007 Since I'm not a mathematician, I tried something easier. I made two blank images in photoshop: a white one at 36x24mm (to replicate film size), and a black one at 27x18 (to replicate the M8 sensor). i multiplied the black 27x18mm frame by the 1.33 crop factor and pasted it on the white 35mm 'film' template. it was the exact same proportion but just a hair smaller. the shape was identical. or, perhaps, there was something i didn't take into account. Correct it's a hair smaller...you had to multiply by 1,3333333... and so on try to multiply by 4 and then reduce by 3.... so you test the precision of Intel (or AMD) math unit... Link to post Share on other sites More sharing options...
sparkie Posted September 27, 2007 Author Share #31 Posted September 27, 2007 AND less DoF at the same aperture compared to the longer lens with full-frame... Don't you mean MORE DoF Jack? ... as Wider focal lengths have a great depth of field ie. more range in focus than their longer brethren Link to post Share on other sites More sharing options...
luigi bertolotti Posted September 27, 2007 Share #32 Posted September 27, 2007 No need to be a mathemetician, just ask any middle-schooler. 27=0.75x36 and 18=0.75x24. Each dimension is reduced by 25%. There is no way, unless a)the sensor dimensions are incorrect, or b)Mr. Shootist lives in a different dimension, that there is more vertically and less horizontally on an M8 shot than a simple crop from full-frame. Well, to be honest I don't think Mr. Shootist lives in another dimension... math is math and the 25% reduction is out of discussion... but I think Shootist intended that when one is taking a specific picture, he is prone to think about what simply "fits in" the framing... reasoning on ABSOLUTE values, not on proportions; and in THIS sense is not at all wrong to say that cropping is different in horizontal and vertical: suppose you take a pic with a 1:10 repro ratio, camera horizontal: if your subject is 8 cm too wide to fit in the M8 frame, it fits in the M4 frame (same lens, same distance) ; if your subject is 8 cm too high to fit in the M8 frame... well it doesn't fit even in the M4 frame... This is not math, but I can understand that a shooter (of course Shootist is ) can reason like this. Link to post Share on other sites More sharing options...
Jack_Flesher Posted September 27, 2007 Share #33 Posted September 27, 2007 Don't you mean MORE DoF Jack? ... as Wider focal lengths have a great depth of field ie. more range in focus than their longer brethren Yes of course I did --- how stupid of me --- and thanks for pointing it out! , Link to post Share on other sites More sharing options...
sparkie Posted September 27, 2007 Author Share #34 Posted September 27, 2007 no worries Jack easy to slip when you're drinking and at the keyboard i remember you from photo.net leica forum. but you left for canon, but came back. are you still shooting canon as well? Link to post Share on other sites More sharing options...
Jack_Flesher Posted September 28, 2007 Share #35 Posted September 28, 2007 no worries Jack easy to slip when you're drinking and at the keyboard i remember you from photo.net leica forum. but you left for canon, but came back. are you still shooting canon as well? To be specific, I left for Canon digital... And yes, I am still shooting Canon digital too --- in fact I just did a job with it today. And yes, I came back too --- the digital M was just too tempting a mistress Cheers, Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted September 28, 2007 Share #36 Posted September 28, 2007 Plus i am in his ear daily and I'm a pest. ROTFLMAO Link to post Share on other sites More sharing options...
lars_bergquist Posted September 28, 2007 Share #37 Posted September 28, 2007 I think you missed my point. A 35mm lens on a M8 would capture less horizontally and more vertically then a equivalent 47mm lens would on a film 35mm camera. Your reference that the Leica 50mm really being 52mm has no real baring on this. It is the size of the sensor, see my above post.This is one reason the wide lenses, or any focal length lens, just don't seem the same on a M8, or any cropped digital camera, compared to a film 35mm camera when taking the crop factor into account. I have seen the development of this thread with mounting horror. It is clear that people do not listen to argument, they KNOW, like any other fundamentalist. And they see what they believe. Reason is simply not operative. I'm out of this. The old man from the Age of Reason Link to post Share on other sites More sharing options...
t024484 Posted September 28, 2007 Share #38 Posted September 28, 2007 At last, someone who can 1. agree with my thinking and 2. explain in simple plain english! Thanks Blakley. I can sleep now:D Having a smaller sensor, means that nothing else but cropping happens. A lens does not care that it has a full frame or a cropped frame behind its rear end. It is true that because of the cropping factor of 1.33, a 35mm on a M8 gives you roughly the same picture as a 50mm on a M7, if taken from exactly the same place. But there is one essential difference, both pictures taken with the same lens opening will show quite different DOF's. Of course the 35mm has quite a larger DOF than the 50mm. The crop factor does also change the viewing angle but not the DOF of a lens. Link to post Share on other sites More sharing options...
michael_b_elmer Posted September 28, 2007 Share #39 Posted September 28, 2007 What is the consensus on this.. Does a 28mm lens on an M8 for instance produce a 37mm 'perspective' or is it still a 28mm perspective with the edges cropped? would like to hear people's thoughts and conclusions.. I think the discussion has become rather chaotic. Sparkies question has not been answered. Since the distance between the film and the lens on a m7 is the same as between the sensor and the lens on the m8, the perspective of a given lens must remain the same - although the sensor only records a smaller part of the picture produced by the lens on the film/sensor plane than the film. Link to post Share on other sites More sharing options...
jaapv Posted September 28, 2007 Share #40 Posted September 28, 2007 It is very simple: as long as you, your subject and the background stay at the same distance the perspective will stay unchanged, irrespective of the lens or the sensor used. The focal length of the lens and the size of the sensor determine the field of view. Link to post Share on other sites More sharing options...
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