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What are the optical advantages of MF over 35MM SLR - Found?
Hello, I posted this subject some time back, and since then have got
myself an old Box brownie to compare the image of the 35mm Film SLR and the Brownie for differences in ratio of FOV between the foreground and background. The differences are interesting, but can anybody with optical design experience tell me what is happening here? The Brownie: http://members.home.nl/brownies/six_20_brownie_d.htm f/11, 100mm, lens, 2 1/4 * 3 1/4 inch film size. Focused on Infinity. The SLR, a old body cobbled together (tight but good fit) with a Minolta 1:1.4 55mm lens. Rear focusing screen made of opaque plastic, and stuck on the back of both. I wanted to post images with the digital on the web, but the focus screen hot-spot on the Brownie is so bad, small and dim, that it was pointless to try. The Test: I used plastic bottles as markers. I put the markers around 30 feet from the camera to each side of the frame of one camera and with the peaks of a mountain range several kilometers away in the background. The cameras were mounted on top of each other (the brownie on it's side) on top of a short wooden step ladder. Result: Not much difference between the FOV of the mountain range above the markers in both cameras. With the very dim MF image (and I was under shade as well) it was very difficult to see the image clearly. I repeated the experiment with the markers now around 15 feet away, still no much difference. The overall Field of View was significantly better on the MF lens. So the experiment seemed to confirm that there is no difference in the ratio of foreground FOV to the background FOV, between the MF and the 35mm. But if there were differences they were too small to see clearly with the focus screens. But then I tried again. Another experiment: I originally was going to rig up two pieces of paper a few feet away to do the experiment, but it was very windy. It then occurred to me that I could use two bottles in front of the cameras to form a slit. With bottles set apart by 2 centimeters to make an slit opening, with the distance of the far opening of the slit the approx the same several centimeters from the lens glass openings on both cameras, there was substantial difference in the FOV of the mountain range through the slit. When the cameras backs were the same distance, instead, the FOV was a bigger difference with maybe double FOV through the slit in the 35mm then the MF. But, the closeup slit itself, on the 35mm, took up around 1/3rd of the image plane, and 1/6th of the plain of the MF. Does this imply that the MF Brownie has more closeup FOV that the 35mm. A bit confusing, I thought the long distance FOV might be smaller on the MF instead. What do you think, it is not the most accurate experiment, can anybody verify this? I am interested if MF FOV does anything to give a truer, to the eye, image. Thanks Wayne. On Sat, 15 Jan 2005 19:50:06 +1000, Wayne wrote: Hi If there is any optic technician/expert that can help me with affirmed knowledge, please reply, it will be most appreciated. I have spent time trying to research this on the web, but from what I can tell: - That the only advantages are professionalism, extreme narrow DOF and higher resolution. That the following does not improve compared to 35mm SLR: - The size ratio between foreground and back ground objects - Angle of view - convergent lines and shape distortion of receding objects - curvature from wide angles (i.e. producing normal looking images with straight lines) - That the only way to solve these problems is through, shift, tilt, swing lenses and altering distance/perspective? Also does it produce a flatter image or more out of focus effect simular to a 35mm zoom lens? Is all this true? Thanks Wayne -- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/ |
#2
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"Wayne" wrote in message
newspsoehv1jtkhyzh5@w... Hello, I posted this subject some time back, and since then have got myself an old Box brownie to compare the image of the 35mm Film SLR and the Brownie for differences in ratio of FOV between the foreground and background. The differences are interesting, but can anybody with optical design experience tell me what is happening here? It's a fairly straightforward principle, Wayne. The longer the focal length, the less the depth-of-field (DOF). The 100mm lens on either the 35mm or the MF camera produce the same DOF at the same aperture. Your observations were hindered by viewing difficulties. I suggest you make prints to see the differences. Earlier you asked if perspective controls (movements) were the only way to get around this and the answer is Yes - with movements such as swings and tilts you change the plane of focus so that it aligns better with the objects you wish to have in focus. I suspect you would truly enjoy using a large format view camera. |
#3
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"Wayne" wrote in message
newspsoehv1jtkhyzh5@w... Hello, I posted this subject some time back, and since then have got myself an old Box brownie to compare the image of the 35mm Film SLR and the Brownie for differences in ratio of FOV between the foreground and background. The differences are interesting, but can anybody with optical design experience tell me what is happening here? It's a fairly straightforward principle, Wayne. The longer the focal length, the less the depth-of-field (DOF). The 100mm lens on either the 35mm or the MF camera produce the same DOF at the same aperture. Your observations were hindered by viewing difficulties. I suggest you make prints to see the differences. Earlier you asked if perspective controls (movements) were the only way to get around this and the answer is Yes - with movements such as swings and tilts you change the plane of focus so that it aligns better with the objects you wish to have in focus. I suspect you would truly enjoy using a large format view camera. |
#4
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jjs wrote:
It's a fairly straightforward principle, Wayne. The longer the focal length, the less the depth-of-field (DOF). Only if the longer focal length results in higher magnification. Move away from you subject when changing to longer focal lengths, such that it still appears same size on film, DOF will remain constant too. The 100mm lens on either the 35mm or the MF camera produce the same DOF at the same aperture. .... and at the same magnification. Compare any lens used on MF with any lens on 35 mm format, both framing the subject the same way, the MF image will have to have higher magnification, thus shallower DOF. (Even when both lenses have the same focal length, and the same aperture is used.) But wasn't this test about FOV, not DOF? ;-) FOV also depends on lens diameter, not just focal length. The ratio of diameter of the lens to the subject size decreases such that for far away (i.e. large) subjects filling the FOV the difference is negligable, while for subjects smaller than the lens' diameter the difference is quite significant. |
#5
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jjs wrote:
It's a fairly straightforward principle, Wayne. The longer the focal length, the less the depth-of-field (DOF). Only if the longer focal length results in higher magnification. Move away from you subject when changing to longer focal lengths, such that it still appears same size on film, DOF will remain constant too. The 100mm lens on either the 35mm or the MF camera produce the same DOF at the same aperture. .... and at the same magnification. Compare any lens used on MF with any lens on 35 mm format, both framing the subject the same way, the MF image will have to have higher magnification, thus shallower DOF. (Even when both lenses have the same focal length, and the same aperture is used.) But wasn't this test about FOV, not DOF? ;-) FOV also depends on lens diameter, not just focal length. The ratio of diameter of the lens to the subject size decreases such that for far away (i.e. large) subjects filling the FOV the difference is negligable, while for subjects smaller than the lens' diameter the difference is quite significant. |
#6
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Q.G. de Bakker wrote:
FOV also depends on lens diameter, not just focal length. The ratio of diameter of the lens to the subject size decreases such that for far away (i.e. large) subjects filling the FOV the difference is negligable, while for subjects smaller than the lens' diameter the difference is quite significant. Uhm... "The diference" being that between two lenses having different diameters. Compare a lens with an 2 cm diameter to a lens with a 8 cm diameter. Both are very small compared to the far away mountain range, kilometers of which span across the horizon in the field of view of both. But put a subject, say a cube, of 4 cm width in front of both lenses, and focus on that and the larger lens will not only see the side of it facing the lens, but its sides too. The smaller lens will only see the side facing it. A similar difference will show in the field of view too. |
#7
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Q.G. de Bakker wrote:
FOV also depends on lens diameter, not just focal length. The ratio of diameter of the lens to the subject size decreases such that for far away (i.e. large) subjects filling the FOV the difference is negligable, while for subjects smaller than the lens' diameter the difference is quite significant. Uhm... "The diference" being that between two lenses having different diameters. Compare a lens with an 2 cm diameter to a lens with a 8 cm diameter. Both are very small compared to the far away mountain range, kilometers of which span across the horizon in the field of view of both. But put a subject, say a cube, of 4 cm width in front of both lenses, and focus on that and the larger lens will not only see the side of it facing the lens, but its sides too. The smaller lens will only see the side facing it. A similar difference will show in the field of view too. |
#8
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Yes, I am talking about a FOV tests here.
So are you suggesting that because the MF lens is smaller that it gets greater FOV at small distances then the larger Minolta SLR lens? So you are saying that if the SLY had a smaller lens than the MF, then the results would be reversed? I will have to test. Thanks Q.G. I wonder if anybody has anymore? Wayne On Tue, 29 Mar 2005 23:13:27 +0200, Q.G. de Bakker wrote: Q.G. de Bakker wrote: FOV also depends on lens diameter, not just focal length. The ratio of diameter of the lens to the subject size decreases such that for far away (i.e. large) subjects filling the FOV the difference is negligable, while for subjects smaller than the lens' diameter the difference is quite significant. Uhm... "The diference" being that between two lenses having different diameters. Compare a lens with an 2 cm diameter to a lens with a 8 cm diameter. Both are very small compared to the far away mountain range, kilometers of which span across the horizon in the field of view of both. But put a subject, say a cube, of 4 cm width in front of both lenses, and focus on that and the larger lens will not only see the side of it facing the lens, but its sides too. The smaller lens will only see the side facing it. A similar difference will show in the field of view too. -- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/ |
#9
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"Wayne" wrote in message
newspsoftwciikhyzh5@w... Yes, I am talking about a FOV tests here. So are you suggesting that because the MF lens is smaller that it gets greater FOV at small distances then the larger Minolta SLR lens? So you are saying that if the SLY had a smaller lens than the MF, then the results would be reversed? I will have to test. This whole thread is beginning to read like Dark Ages mythology. (then someone else said) But put a subject, say a cube, of 4 cm width in front of both lenses, and focus on that and the larger lens will not only see the side of it facing the lens, but its sides too. The smaller lens will only see the side facing it. So if I use a large enough lens, I should be able to see all six sides, right? Man, this is getting stranger and stranger. |
#10
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"Wayne" wrote in message
newspsoftwciikhyzh5@w... Yes, I am talking about a FOV tests here. So are you suggesting that because the MF lens is smaller that it gets greater FOV at small distances then the larger Minolta SLR lens? So you are saying that if the SLY had a smaller lens than the MF, then the results would be reversed? I will have to test. This whole thread is beginning to read like Dark Ages mythology. (then someone else said) But put a subject, say a cube, of 4 cm width in front of both lenses, and focus on that and the larger lens will not only see the side of it facing the lens, but its sides too. The smaller lens will only see the side facing it. So if I use a large enough lens, I should be able to see all six sides, right? Man, this is getting stranger and stranger. |
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