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08/07/2006 02:23:47 AM · #1 |
I used to shoot 35mm, though I was never a "photographer" in the knowledge sense of the word.
I've heard this brought up numerous times, and my dad (who was solely a 35mm photographer for years) keeps telling me I'm full of it.
Can *someone* explain this mythical "35mm vs. digital" focal length difference?
I'm really missing something, here. |
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08/07/2006 02:37:20 AM · #2 |
| I found this site very helpful in learning aboout crop factors, FoV and AoV |
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08/07/2006 02:41:14 AM · #3 |
as a quick summary:
digital cameras with smaller-sized sensors need only a shorter focal length lens to achieve the equivalent focal length effect of 35mm film cameras
did I just make you more confused? :p
Message edited by author 2006-08-07 02:42:11. |
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08/07/2006 02:44:34 AM · #4 |
Basically: (I think)
A digital camera's image sensor is smaller than a piece of 35mm film, but the image coming in through the lens is the same.
This means only the centre part of that image is captured by the sensor.
This means it looks more zoomed in because the edges are missing.
This means you need a much wider lens to get the same result as a less-wide lens in 35mm.
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08/07/2006 02:45:12 AM · #5 |
Multiply your lens by 1.6X (Rebel XT crop factor) and you get the 35mm equivalent if you put it onto a your Rebel XT.
Message edited by author 2006-08-07 02:56:36. |
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08/07/2006 02:46:33 AM · #6 |
| Look up APS-C sensor and you will find some more info. |
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08/07/2006 02:47:12 AM · #7 |
Originally posted by faidoi:
Multiply your lens by 1.6X (Rebel XT crop factor) and you get the 35mm equivalent if you put it onto a 35mm camera. |
I think the 1.6x figure is actually the equivilent that you get when you put it on your Rebel XT. The number on the lens is correct for a 35mm. |
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08/07/2006 02:55:39 AM · #8 |
Thank you... very helpful. Just in the first page I went "OH!" |
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08/07/2006 02:56:17 AM · #9 |
Originally posted by Konador:
Originally posted by faidoi:
Multiply your lens by 1.6X (Rebel XT crop factor) and you get the 35mm equivalent if you put it onto a 35mm camera. |
I think the 1.6x figure is actually the equivilent that you get when you put it on your Rebel XT. The number on the lens is correct for a 35mm. |
Changed. |
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08/07/2006 06:00:59 AM · #10 |
Originally posted by Konador:
Originally posted by faidoi:
Multiply your lens by 1.6X (Rebel XT crop factor) and you get the 35mm equivalent if you put it onto a 35mm camera. |
I think the 1.6x figure is actually the equivilent that you get when you put it on your Rebel XT. The number on the lens is correct for a 35mm. |
The number on the lens is always correct (except for some p&s models). A 200mm is always a 200mm, doesn't matter if you put it on a medium format, a 35mm camera or an APS-C camera. You just get a diffent field of view and need to be aware that you use the right design for your camera (using a Canon EF 200 on your 6x4 will cause a massive amount of vignetting, just like using an EF-S on you 35mm camera, while using a mf 200mm on you APS-C -when it fits- should be possible without any vignetting).
All P&S manufactures use it because it looks marketingtechnically silly to use the real focal lenghts of those lenses. Look on the barrel or on the front, usually there are some odd numbers like 13-34mm or something like that. On the other hand is is not silly, because there are so many different sizes of sensors in this segment that a buyer has no clue how to compare them. For dSLR this is less of a point because there are basically 2 formats, APS-C and full-frame (the 1.3x 1D is not a big market for consumers).
For dSLR users this 35mm equivalent stuff is way overblown. When you use APS-C and think APS-C you just work with the numbers on the lens. I seldomly read from MF shooters that they quote their lens length in 35mm equiv, nor 35mm shooters recalculating to MF for example. IMHO of course.
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08/07/2006 03:15:22 PM · #11 |
| Ok I understand the whole 1.6 crop factor bit on DsLRs with APS-C size sensors. But i'm confused about one thing. On my Fuji S602z the lens has written on it: f=7.8-46.8mm, yet on DPreview it says 35-210mm. Does that mean if I want the equivalent of this lens in a DSLR I'll need about 22-131mm lens given that 1.6 crop factor? |
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08/07/2006 03:29:27 PM · #12 |
yes if by DSLR you mean a 1.6 crop factor sensor like the XT ..
Message edited by author 2006-08-07 15:29:50. |
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08/07/2006 03:32:29 PM · #13 |
Originally posted by ionyou:
Ok I understand the whole 1.6 crop factor bit on DsLRs with APS-C size sensors. But i'm confused about one thing. On my Fuji S602z the lens has written on it: f=7.8-46.8mm, yet on DPreview it says 35-210mm. Does that mean if I want the equivalent of this lens in a DSLR I'll need about 22-131mm lens given that 1.6 crop factor? |
Yes.
The actual lens focal length is 8-46.8mm, that's the zoom range. DPreview has calculated the 35mm equivalent for this lens on that camera.
35mm equivalent is 35mm, divided by 1.6 = 22mm.
Fuji S60 8mm, APS-C 22mm, full frame 35mm, these lenses all cover the same field of view at their respective sensors. Incidentally, this shows you why DOF is so extreme on the point-n-shoot cams...
R.
Message edited by author 2006-08-07 15:33:32.
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08/07/2006 03:40:10 PM · #14 |
Originally posted by Bear_Music:
Incidentally, this shows you why DOF is so extreme on the point-n-shoot cams...
R. |
Ok I don't see what that has to do with DOF. My Fuji s602z for example has DOF selectable from 2.8-11. Is this different than a 2.8 aperture lens on a DSLR with an APS-C sensor? |
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08/07/2006 03:42:42 PM · #15 |
Originally posted by ionyou:
Originally posted by Bear_Music:
Incidentally, this shows you why DOF is so extreme on the point-n-shoot cams...
R. |
Ok I don't see what that has to do with DOF. My Fuji s602z for example has DOF selectable from 2.8-11. Is this different than a 2.8 aperture lens on a DSLR with an APS-C sensor? |
Aperture is a ratio, so the smaller size of the Fuji's sensor and lens and whatnot will still be the same ratio equalling F/2.8 as a dSLR with a F/2.8 lens.
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08/07/2006 03:43:47 PM · #16 |
Originally posted by ionyou:
Originally posted by Bear_Music:
Incidentally, this shows you why DOF is so extreme on the point-n-shoot cams...
R. |
Ok I don't see what that has to do with DOF. My Fuji s602z for example has DOF selectable from 2.8-11. Is this different than a 2.8 aperture lens on a DSLR with an APS-C sensor? |
DOF is a function of the physical size of the aperture. F/stop is a ratio of the aperture diameter to the focal length of the lens. In other words, a 25mm aperture on a 50mm lens is f/2.0, while a 25mm aperture on a 200mm lens is f/8.0.
Accordingly, f/2.8 on an 8mm lens is a LOT smaller in physical size than f/2.8 on a 35mm lens, and it therefore has much more DOF.
R.
Incidentally, this is why many people are bitterly disappointed in their macro shots when they move from a point 'n shoot to a dSLR: DOF at macro range on a dSLR requires stopping down MUCH further, which means in anything but very bright lighting handholding becomes problematical.
Message edited by author 2006-08-07 15:45:59.
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08/07/2006 04:21:27 PM · #17 |
| on the other side, you cannot get the nice bokeh ( shallow DOF ) with a point and shoot unless you place your object 10 mm away from the lens and the background at infinity... |
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08/07/2006 04:29:30 PM · #18 |
Ah I see now. Thanks for answering all my questions. I was unaware fstop was a ratio. I just knew f2.8 meant shallow DOF and more light gathering ability but now I see aperture is not the same as fstop, just related (by the lens focal length) Oh on second thought I did know that! I just forgot it, I just remembered my 2032mm focal length telescope with 203.2 mm aperture (8") is an f/10 scope! Doh. How quickly we forget sometimes.
So does this mean P&S small sensor sized cameras are better for macrophotography than DSLRs? Or is there a way around this with the right lens on a dslr? |
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08/08/2006 03:45:09 AM · #19 |
| i wouldnt say better... stopping down with IS and good light should do well... |
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08/08/2006 03:54:19 AM · #20 |
Originally posted by ionyou:
So does this mean P&S small sensor sized cameras are better for macrophotography than DSLRs? Or is there a way around this with the right lens on a dslr? |
If "better" means more DOF when handheld, then the answer is basically yes.
R.
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