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12/16/2005 06:17:41 PM · #76 |
Originally posted by AJAger:
Originally posted by nsbca7:
If it is the same lens the compression will be the same regardless of the body it is mounted on or the "crop factor". If the lens is a different focal length the compression will change. |
Quite simply, the compression depends upon the ratio of the camera to subject and the camera to background. If the camera, the subject and the background are kept in the same positions, then the compression will be exactly the same, no matter what lens is used to take the photograph. |
Quite simply, BS. Take some pictures with your lenses and look at them. You can't just make up theories like that and call it fact.
A wide angle lens will make things close up appear larger then objects in the background and a telephoto will cause subjects that are back further in the background to appear closer to objects in the foreground. This is basic Photography 101 stuff. C'mon. |
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12/16/2005 06:41:29 PM · #77 |
Quite simply not BS and absolutely not made up and very definitely a fact. This is very basic mathematics. The only reason that a wide angle lens makes objects in the background appear smaller in relation to the subject is that the photographer gets closer to the subject. The converse is true with a telephoto lens. This is the subject of an extremely widespread mis conception in photography, even amongst people as experienced as you. Let me give an example:
If you have two people of equal height, one standing 100 feet away from the photographer and the other standing a further 100 feet away, then the ratio of distances is 100:200, so that the person in the foreground looks twice as large as the person in the background. If the photographer moves fifty feet closer, then the person closest to the camera is fifty feet away and the second person is 150 feet away. The ratio is now 50:150 or 1:3, so the person in the forground looks to be three times larger than the person in the background. If the photographer now moves so that he is 1 foot away from the first person, then the second person is 101 feet away. The ratio is 1:101, so the person in the foreground appears to be abou 100 times larger than the person in the background.
Following this, I urge you, if not convinced to take some photos and see for yourself. Try, for example, mounting a camera on a tripod and taking some shots of a scene with suitable depth using various lenses. When you get the shots into Photoshop, overlay them and rescale (obviously, those shot with shorter lenses will need to be enlarged), so that the sizes of the elements within the frame are equal. The photos will match.
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12/16/2005 07:07:20 PM · #78 |
Here's a quick test, as I'm unable to get to sleep. Not great shots, I freely admit, but I feel that they illustrate my point.
This one was taken at 16mm.
This one was taken at 35mm.
Both of these shots were taken with the camera resting on the table and the only alteration made between taking the two shots was to zoom in.
The first one was cropped to match (albeit loosely, it's nearly midnight here, you know) the framing of the second. If you look at the tin in the foreground and the bottle in the background (overlooking the fact that the bottle is somewhat out of focus in the second shot), you can see that there appears to be no difference. As I said, it's not the focal length that compresses a scene, it's the distance from the camera. DOF, however obviously changes with focal length and I'm not disputing that.
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12/16/2005 07:07:38 PM · #79 |
| I've always understood that lenses that are longer compress and wide angles expand. Wide angles do this far more than long lenses. If you take a 14mm lens on FF it's going to be very heavyily stretched due to perspective (and distortion). The perspective of the lens is going to be the same as the crop of the FF on a 1.6x camera. If that's true, then you can't change the rules for long lenses. putting a 200mm lens on a 1.6x crop camera surely doesn't make it a 320mm lens. |
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12/16/2005 07:13:51 PM · #80 |
Originally posted by kyebosh:
I've always understood that lenses that are longer compress and wide angles expand. Wide angles do this far more than long lenses. If you take a 14mm lens on FF it's going to be very heavyily stretched due to perspective (and distortion). The perspective of the lens is going to be the same as the crop of the FF on a 1.6x camera. If that's true, then you can't change the rules for long lenses. putting a 200mm lens on a 1.6x crop camera surely doesn't make it a 320mm lens. |
Ultimately, the point I'm making is that a lens does not have a 'perspective'. It's a matter of where the photographer stands. It's very difficult to make a comparison between an ultra-wide angle lens and a telephoto as in my previous post, as two objects framed in a telephoto lens would only appear as specks when photographed at wide angle.
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12/16/2005 07:18:11 PM · #81 |
| i'll perhaps try a test later tonight at 17mm and 50mm and 100mm if i can get all my focal lengths to agree on a subject. From what i've noticed looking through the lenses, there is a difference. |
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12/16/2005 07:20:27 PM · #82 |
Originally posted by kyebosh:
i'll perhaps try a test later tonight at 17mm and 50mm and 100mm if i can get all my focal lengths to agree on a subject. From what i've noticed looking through the lenses, there is a difference. |
I'm absolutely confident that your results will agree with the test above. Have fun.
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12/16/2005 07:58:28 PM · #83 |
Originally posted by kyebosh:
i'll perhaps try a test later tonight at 17mm and 50mm and 100mm if i can get all my focal lengths to agree on a subject. |
Perhaps you could post your results in this thread ?
I for one am curious as I have a link to page which demonstrates the compression effect but the distance to subject was changed for each shot.
bazz.
Message edited by author 2005-12-16 20:05:03. |
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12/16/2005 08:31:05 PM · #84 |
| working on it now... 17, 35, 50, 100mm |
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12/16/2005 08:38:33 PM · #85 |
Here they are shot from the same place with the FF (1.25x) resized. the center of the frame is always the top of the further lens of the glasses. These are all F8, 1/500, iso 400, and underexposed (i blame my flash, and myself for not looking at the histo).
I'll work on resizing them all to fit the size of the 100mm example there.
forgot the link lol
//photobucket.com/albums/v494/kyebosh/perspective/
Message edited by author 2005-12-16 20:38:54. |
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12/16/2005 09:01:16 PM · #86 |
| done! check out the link in my last post. Overlay them in PS if you want. They might not be exactly scaled the same size but they're very close. |
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12/17/2005 12:25:21 AM · #87 |
Good job Kyebosh. Lotta work to prove what's a simple and irrefutable fact: a lens changes NOTHING in the relationship between objects.
The "compression myth" originates because people mistakenly "test" it by moving the camera so the "subject" has a fixed size as the lenses are changed. You'll definitely see a change in "compression" (if you want to call it that) if you move closer and mount a wider lens.
But if you mount a camera on a tripod and shoot the same scene with different lenses, if you crop all the resultant shots to show the same area of the image, you'll get precisely identical images. Your test is the proof of that.
Robt. |
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12/17/2005 01:25:07 AM · #88 |
So this is definitely not BS, then?
As Bear says, a lotta work to prove an irrefutable fact. I suppose that this myth is so widely and easily accepted that nobody wants to give it up easily.
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12/17/2005 01:31:00 AM · #89 |
Originally posted by chafer:
I was curious if/why Canon does not come out with any major overhauls of their lens series. The 70-200 has been around for years...will they ever come out with something new? Do they NEED to? I would like to buy a 70-200 (non IS version...for cost reasons), but I was curious if anything comparable is on the way any time soon...something new? Maybe a new lens of that focal length would drive the current IS price down. |
If they improved it any, we woudln't be able to afford it :)
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12/17/2005 11:37:56 AM · #90 |
| gonna have to agree, i find that it's not BS. Thanks for the info AJ. |
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12/17/2005 11:50:13 AM · #91 |
Originally posted by AJAger:
So this is definitely not BS, then?
As Bear says, a lotta work to prove an irrefutable fact. I suppose that this myth is so widely and easily accepted that nobody wants to give it up easily. |
It's the single, most widely-accepted "myth" in photography, at least as far as "significant" myths go. When I was teaching, every single student would come into my beginner's class believing this myth ΓΆ€” there were no exceptions.
There's another "myth" that I've only just become aware that I was wrong on myself, all these years, but it's a more subtle one: one of the reasons I bought the 60mm macro instead of the 100mm macro is that I'd get more DOF, right?
Wrong.
At a given reproduction ratio, DOF is identical. No matter what lenses we compare. I still have a hard time believing that, but it's true.
Robt. |
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12/17/2005 12:05:10 PM · #92 |
Originally posted by nsbca7:
Originally posted by AJAger:
Originally posted by nsbca7:
If it is the same lens the compression will be the same regardless of the body it is mounted on or the "crop factor". If the lens is a different focal length the compression will change. |
Quite simply, the compression depends upon the ratio of the camera to subject and the camera to background. If the camera, the subject and the background are kept in the same positions, then the compression will be exactly the same, no matter what lens is used to take the photograph. |
Quite simply, BS. Take some pictures with your lenses and look at them. You can't just make up theories like that and call it fact.
A wide angle lens will make things close up appear larger then objects in the background and a telephoto will cause subjects that are back further in the background to appear closer to objects in the foreground. This is basic Photography 101 stuff. C'mon. |
It might be helpful for me to interject here WHY most people believe the "myth" so well-expressed by nsbca:
Suppose you are trying to take a head-and-shoulders portrait of your son standing on a pier with a large-city skyline behind him. You start out shooting him with a 200mm lens, and the buildings really LOOM behind him. You wonder if this is optimum, so you decide to move down the pier and zoom out to 100mm. This looks better, so you move in even further and zoom out to 70mm. Since, each step of the way, you've filled the same portion of the frame with his head-and-shoulders, and each step of the way the buildings get smaller and smaller in the background, you decide to mount a WA lens and move in even closer. It's no surprise to you that the buildings virtually disappear in this shot; it's exactly what you expected.
So, obviously, telephoto lenses compress more than wide angle lenses, right?
Actually, NO. What's changing here is the physical relationship of the camera to the subject. When you want more "compression" you need to step further back, and when you step further back you have two choices: you can zoom up to telephoto range or you can crop in on the wider shot to emulate that zoom. Each produces the same visual relationships between subject and ground, although obviously zooming in to eliminate cropping produces a "better" image detail-wise.
You can actually USE a 200mm lens as a 400mm lens, for example, if you're willing to accept the quality tradeoff that comes from such cropping. In DPC, at 640 pixels, there's essentially no falloff in quality if you use the "crop zoom" to turn your 200 into a 400, although you'll see some degradation in, say, an 8x10 print, and quite a lot in a 16x20.
Robt.
Message edited by author 2005-12-17 12:05:45. |
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