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Old Feb 28, 2007, 5:30 PM   #1
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If you use the same lens on a Canon 30D (which is 8.2megapixils) and a Canon 5D (which is 13megapixils) and are printing an 8x10 print lets say and you shot the same subject in raw and converted it to highest Jpeg, will the photo resolution quality be the same or will the 13meg camera be better? If it is better, that would mean a Rebel XTI at 10megs would be better quality also than the 30D if you used the same lens too. Right?
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Old Feb 28, 2007, 6:44 PM   #2
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Everything else being equal, more megapixels means higher resolution. In your case, the lens was the same, but the sensors were different.

The top quality images for the 3 cameras you chose were:

4368 x 2912 - 5D

3,888 x 2,592 - XTi

3504 x 2336 - 30D

Most printers top out at 300 DPI. All three of the cameras would be close to or over 300 DPI for an 8" X 10" print. Therefore, I think you wouldn't notice much if any difference between them. There was an article in the NY Times by a guy who tried to prove that most people couldn't tell the difference in prints made from cameras much more dissimilar than these three cameras are. I think the difference in price is due to differences in:

1. performance - How long does it take the camera to get ready to take the first picture. What is the lag between successive pictures? How many shots can you make in continuous mode without stopping?

2. build quality - magnesium alloyversus durable plastic

3. (maybe) slight differences in low light performance - both focusing speed and image quality (low noise)


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Old Mar 1, 2007, 1:42 AM   #3
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Things are always more complicated than just a single number.

The 5D has a pretty big difference with the 30D in that it uses a full frame sensor. This is why it is able to shoot at such a high resolution without any loss in quality or low light performance. However, this also means that the camera sees something different than the 30D.

If you shot the exact same scene from the exact same spot using the same settings and the same lens at the same focal length, the 5D would look like it was taken from farther away because of it's wider field of view due to it's larger sensor. This means you'd either need to crop the picture which would then be closer to the resolution of the 30D, take the picture closer which would change the scene and lower your depth of field, or increase the focal length which might not even be an option.

Also, in order to see a visible improvement with that higher megapixel, you need to use more expensive lenses which can resolve more detail. If you use some $50 zoom lens, you'd likely get the exact same actual resolution out of both cameras.

Now if what you're really trying to get down to is whether or not higher megapixel means higher quality, it can mean that if you need to print extremely large or if you need to crop a lot, AND you have enough light to get very clean exposures.

Otherwise, extra megapixels can actually be a drawback as your files will be larger, working with them will be slower, and when more megapixels are crammed on the same size sensor, you tend to increase noise levels and lose useable dynamic range. Personally, as long as I have enough resolution for whatever my output will be, I'd take extra dynamic range over megapixels any day.
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Old Mar 1, 2007, 6:51 PM   #4
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Thanks for the info. It sure gets confusing. I found it easier with film.... I'll probably get the 30D also for backup and its smaller files. Just shoot the wedding reception with that one and the portraits with the 5D. I have a feeling Canon is going to come out with a 10meg. 30D camera like the XTI Rebel wich is 10megs.
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Old Mar 2, 2007, 2:55 AM   #5
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I've worked with the 5D personally, but I haven't worked with the 30D or 20D so I don't really know all the differences between the cameras in-depth. I also haven't shot weddings before, so I'm just wondering, why you would choose the 30D over the 5D in that instance?

From what I've heard, the 5D is about as good as it gets for shooting in low light, and from my own experience I believe it. Does it have to do with the lenses you've budgeted for? I guess to get the most of the 5D, you'd want to use L series lenses. The only advantage I could think of is that the 30D would probably be a lot lighter since you could use EF-S lenses with it of shorter focal length. I used the 5D with an L series 28-105 and it got heavy fast.


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Old Mar 2, 2007, 8:30 AM   #6
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If you take the lens off of one camera and screw it onto another (DSLR) camera with a smaller sensor, the 35mm focal length equivalent becomes greater. Specifically you have to multiply by the crop factor which is the diagonal of the first camera's frame or sensor divided by the diagonal of the second camera's sensor. The crop factor for your lens on the second camera may or may not be published so you may have to do the calculation yourself. Meanwhile the absolute focal length and the size of the focused picture inside the camera remains the same. To get the same angle of view you have to adjust the zoom to get the same (final) 35mm equivalent focal length,or stand in a different place.

The lens' resolution in line pairs per millimeter at the focal planeof course stays the same. With the lens on the camera with the smaller sensor, the total number of line pairs resolvable across the picture height will be less.Since the resolution of the lens is better near the center, the resolution of the lens in terms of pixelsall the way across thesmaller sensorismore than suggested by the proportionately smaller size.

Digital camera hints: http://members.aol.com/ajaynejr/digicam.htm


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