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| 送交者: 30D 2007年07月27日00:00:00 于 [茗香茶语] 发送悄悄话 |
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You can crop as much as you like. You can shoot with a portrait lens and crop down to the field of view of a spotting scope. There just won’t be much detail left.
If you crop a 5d to match the field of view of a 1.6 crop factor camera, you will have a 5 megapixel image. IIRC, the highest resolution 1.6 crop Canon is currently 10MP, so the equivalent cropped area of a full-frame, 12MP 5d will have noticeably less detail than the equivalent image from a 400d.
If the rumors are correct and Canon releases a 22MP, full frame DSLR, it will have better detail (even cropped) than an 8MP 1.6 factor camera, but just barely. It will still have less absolute resolution (after cropping, for a given lens) than a 400d. If you’re trying to photograph something that only fills a fraction of the frame with the longest lens you have, and you absolutely want the most detail possible when you crop the rest of the image out, you don’t want a 5D. That’s not what it’s designed for. (You really want a D2X – that is what it’s designed for – but there’s the issue of lens investment, etc…)
If you’re not trying to wring as much tele detail as possible out of your system, the 5d has a lot going for it. (Like… pretty much everything else.)
(I think this thread has pretty much run its course. I’m taking any additional follow-ups off the alias.)
Will
From: Glenn Wasserman
you're saying, even if we CROP the shots in photoshop to something like 5-6mp, we still won't have the angle of view we're used to?
Or, "can I crop a 5D image to compensate for the wider field of view and get back the 'reach' I lose by going full frame"???
From: Will Peterman (Volt) Nope. They’ll get shorter. If you’re (say) a birder and you want as many pixels as possible of something fast and far away, you might do better to put your lottery winnings into the new sports body (1.3 crop factor, 10mp, I forget the model but I’m sure every Canon shooter on the list can tell me J )
The 5d is a great camera (I want one in an F mount) but for sheer reach-out-and-touch-it-ness it’s not the top of the line.
From: Glenn Wasserman
So from a practical sense, for those of us who have crop sensor bodies and hope to win the state lottery and one day get a 5D, can we crop the image to make it the equivalent or better than the images we get now.. But maintain the "effective focal length" we have now with the 1.6x factor?
If you put a 5D on a tripod, lock the head, take a photograph, take the lens off the 5D, put it on a 30D, put the 30D on the same tripod, and take another photograph, and then view both photographs at 100% in Photoshop (which I think is equivalent to what you mean by ‘actual size’: each pixel on the screen corresponds to a pixel in the photograph), they will not be the same.
Objects in the 5D image will be smaller. If you have a 30D image that you like, you know exactly where and how it was taken, and you want to use a 5D to produce a pixel-by-pixel copy, you can’t do it by cropping. You have to change the focal length of the lens. Specifically, you have to zoom in: I think increasing the focal length by a third would be about right, but I won’t swear to the exact value. (Increasing it by a factor of 1.6 would be too much.)
Another way to phrase it (basically what Steve said in the first place) is that an image covers fewer pixels when it is projected on to the sensor of a 5D than when it is projected on to the sensor of a 30D with identical lenses. The pixels on the 5D sensor are physically larger and their centers are spaced farther apart.
From: Paul Cheng
I, however, believe Joshua and my hypothesis are correct. I know when we fit the images to the screen, the object in the 5D pic is smaller. I think that’s what has caused all kinds of confusion.
After reading all of your explanations, I can simplify problem more: · Take the same object from the same distance using the same lens but using 5D and 30D respectively. · Show both pictures in windows, but rather than fitting them to the screen, expend to the actual sizes. · The question is whether two objects now from those 2 pictures will be the same size?
According to my understanding from Wikipedia of crop factor, they should be the same size.
From: Caleb Pong (Echo Services Inc)
My maths corroborate with Will's. Cropping a 5D by 1.6 gets you almost exactly 5mp. Also, the object in the cropped-to-8mp image from the 5D will be about 20% smaller than the 30D. (20% by the x-dimension, not by area.)
Caleb
From: Will Peterman (Volt)
The math is easy enough. A 12mp 3:2 sensor is about 4200 pixels on the long side; an 8mp crop of the same sensor would be about 3500 pixels. 4200/3500 means the crop factor is about 1.2, so it has a wider angle of view than a sensor with a crop factor of 1.6. The hypothesis can be rejected. J
To get a crop factor of 1.6 (and the same angle of view as the 30D), you’d have to crop the 5D to less than 5mp.
From: Paul Cheng
Ok let me rephrase it. This is the hypothesis: 1. From the same distance with the same lens but different cameras 30D and 5D, I take a shot respectively of the same object. 2. The picture from 5D will be 4368x2912. I crop that down to 3504x2336 to match the one produced by 30D. 3. Now 2 pictures is identical in terms of the size of the object. |
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