Much ado about nothing (or everything)

[mark_james]

Stupid title -- stupid post... Maybe. With a bit of caution and optimism I bought the 5D

and 24-105 IS. I have a Digital RebelXT and various rediculously expensive lenses. Like

many, I checked the sharpness of the 24-105 IS against my 24-70/2.8, which I consider

sharp. I was nit picking over this little difference vs that little difference. Then I tried my

28-105/3.5-4.5. At f8 is was surprisingly close to the other two with the 5D. Before I

packed up I tried all three on the Digital RebelXT. I adjusted the zoom for the same field

of view and upres'd the RebelXT image to the same resolution as the 5D. Wow! All this

worry about putting the best possible glass on a camera is, for me, a moot point. It's all

about the sensor and all the rest is in the fuzz. The 5D had a world more detail. Maybe

my 24-105 is a bit less sharp than my 24-70, but I don't care, because the whole setup

has so much more detail than the RebelXT as to be in, well, yes, a different league. No

more resolution/sharpness tests. I'm just going to shooooot.

[trothwell]

Mark: can you post some sample comparison photos? I also have a RebelXT, and have been

contemplating getting the 5D. I would like to see what kind of difference to expect.

[neild]

Excuse me, perhaps I'vbe mis-understood you... but surely, if you up-res images, the details will diminish? Perhaps for a comparison you should be down-resing your 5D files? No, that won't do either. You should not zoom to the same FOV - you should instead shoot the same focal length and treat the dRebel as a crop of the 5D (which it is). You should then compare the files without changing either of their sizes.

[shambrick007]

"but surely, if you up-res images, the details will diminish?"<p>Yep. I'm at a loss too with this comparison....

[PuppyDigs]

Who cares if the comparison is fair? The only thing that counts is if you're happy with the

results. And I bet most folks would be happier with a 5D than a Rebel fair comparison or

not.

[daniel_taylor]

"Then I tried my 28-105/3.5-4.5. At f8 is was surprisingly close to the other two with the 5D."

 

Sure...at f/8. If you always shoot at f/8 or above then you don't need the most expensive glass. Expensive glass is expensive because of its performance wide open. And often because of other subtle things like flare and bokeh. (While we're at it...the 28-105/3.5-4.5 is very good at the tele end and good at the wide end to. Many other low cost "consumer" zooms will get spanked even at f/8 by your L zoom or by the 28-105/3.5-4.5.)

 

"I adjusted the zoom for the same field of view and upres'd the RebelXT image to the same resolution as the 5D."

 

The real practical test is to produce prints at your most common size. For most serious amateurs this is 8x10. (For most snapshooters it's 4x6.) I bet you won't see too much, if any, difference in 8x10's at normal viewing distances, between bodies or lenses at f/8, all other things equal. It's at larger sizes that the 5D really starts to shine.

[John Crowe]

I agree with Mark's method. When I have directly compared 35mm to 6x6 to 4x5 I have used the closest focal lengths that I could to provide the same field of view of a particular landscape taken from the exact same spot. When I test 35mm lenses against 35mm lenses I adjust the shooting distance to provide the same field of view of a target. Comparing 35mm slides meant viewing them all at the same magnification of 10x. Ideally I would view the various transparency formats at the appropriate magnification to make the final image size identical ie 35mm at 10x, 6x6 at 5x, and the 4x5 at 2.5x. (just approximates). To compare various DSLR formats you would have to do the same thing. Compare them so the final image dimensions in inches is equal. Obviously one format will have more or less resolution within that physical size and that is what you want to compare.

 

 

If you are shooting something, like distant race cars, where you find the crop favourable in a smaller format DSLR then by all means crop the 5D image to the same view and compare resolution at equivalent image size to determine if it is worthwhile keeping a smaller format DSLR for telephoto shots, while using a full frame camera for wideangle shots.

 

 

By the way Mark you admittedly have too many lenses so please send me a couple. Thank-you, John.

[mark_james]

Thanks John. Yes, it was a crude attempt at comparing equivalent print sizes. I often print 11x17 and like to occasionally go larger. Thus the choice to use equivalent FOV and up-rez the RebelXT. Trevis, I realized afterwards that I had set default parameters on the 5D and lowest sharpening on the Rebel XT. I would have to redo the test properly with raw rather than JPEG to satisfy most people here. I'll see what I can do with the little time available. Daniel: As you point out,the 24-70/2.8 is probably significantly shaper than the 28-105/3.5-4.5 when testing with resolution charts and X Pan B&W film (or similar very high resolution film). But the pixel size for the 5D is not particularly high (compare for instance to the Nikon D2X or D200). To some of the others: The test was at 50 mm and f8. There are many other variables that I did not test. No doubt the best possible glass will improve many characteristics of the image (contrast, color, detail, just to name a few). I am still convinced that there is a world of difference between the cameras for my purposes. I also believe that if I only had the 28-105 and couldn't afford both a 5D and 24-105, my ability to print big would not be hampered significantly by the 28-105 on the 5D. Said another way, I would rather shoot with a 5D and 28-105 than the Rebel XT and 24-70. YMMV.