How much are you dying to get your hands on a 5D Mark II?

[Daniel Browning]

Thanks for the additional info.

It's my pleasure. One day I learn something from you, the next it's vice-versa, sharing knowledge is fun.

The point of having wide apertures (for me, at least) is enabling a small depth-of-field, lowing the ISO needed, or permitting to use faster shutter speeds.

Agreed.

If I take a picture using the 17-55mm on a 50D, at 20mm and f/2.8, won't I be letting in twice the amount of light than if I take the same picture with the 24-105mm, at 32mm and f/4 (at these settings, the 1.6 multiplier means the subject is framed exactly the same for both shots)?

Kind of. Yes, at f/2.8 you will be letting in twice the amount of light *per area*, but the total amount of light captured will be much smaller. For example, the lens on a very tiny 1/1.7" Digicam with a 7mm f/2.8 lens also has the same perspective/FOV as your 20mm, and it also captures the same amount of light per area, but the total amount of light falling on the sensor is much less. In fact, f/2.8 on a digicam is the same amount of light as f/14 on your 50D! (And f/19 on the 5D2.) It's no wonder digicams struggle in low light. The reason is sensor area.

In the same way, a full-frame f/4 lens focuses more light than an f/2.8 APS-C lens: it's just spread out over a wider area. So the full-frame camera has about a 1/3 stop advantage in low light at f/4: you could upgrade to the 5D2 and 24-105 f/4 and still get all the same DOF, noise level, and shutter speed. In fact, it's more than a 1/3rd stop better at f/4.

Of course, if you take it even further, and go with f/2.8 on the 5D2, then you'll have a 1.4 stops thinner DOF, and that much more low light power.

Are you saying that because I'm using a 1.6 crop sensor, the equivalent aperture on the 50D would be narrower on a full-frame sensor?

Yes. To get the same depth of field on a full frame sensor, one must stop down approximately 1.4 stops. Since f/4 is only 1 stop, shooting the 24-105 wide open will give you less depth of field (and more total light).

You also said that the front element of the 24-105mm is larger, but I'm not quite sure what you mean and how that's relevant?

I shouldn't have mentioned it: the front element just confuses things. But since I did, I should explain. The front element is the entrance pupil, i.e. the big piece of glass that your brides see on the front of your lens. Generally, the aperture (not focal ratio) determines the size of the front element. A 400mm f/5.6 has an aperture of 71mm (400/5.6=71), just like the 80mm f/1.2 (80/1.2=70), so the front element of both lenses will be a certain size. Sometimes they are larger for higher quality (less vignetting) or other optical design reasons. If you compare the front elements of the 17-55 and 24-105, you'll see that the L has a bigger one. Generally, this means that it is longer, faster, or has a bigger image circle. In the case of the L compared to the 17-55, it is longer, slower, and a bigger image circle. Clear as mud?

I'm really lost on this one. Do you have a site that I can check out that maybe goes a little more in-depth?

Yes! I'm glad you asked. There is one web page that explains all of this, and more, in excrutiating detail.

http://www.josephjamesphotography.com/equivalence/

But I would be happy to answer any additional questions about this topic.

--
Daniel

[Robert Fronckowiak]

By pure dumb luck, K&S Photo in Palo Alto, CA had one on the shelf when I stopped by before Xmas. I actually went in looking for the 5D, only to have the sales guy tell me all they was the mark II. Needless to say I jumped on it, and have been very pleased with it. I am not a pixel peeper, so I couldn't tell you if my 5D suffers the same ills as others have demonstrated on other forums. I do have some pictures up, if your curious in seeing what the 5D MkII & the 24-105L lens are capable of. I use a program called SandVox on the Mac that makes it easy to post pics, but I do not know what type of image compression they do when building html and web pages. So that said, any compression or other nasties you see in the picture are not the 5D's fault, as once you see the images on your computer, I have no doubt you'll be impressed with the image quality.





http://www.rjfimage.com/featured_gallery/

[David Selby]

after seeing how every Canon rebel and 50d etc.. has tanked in price within a few months of release - I can not in good concious purchase until i see some discounts

[Dawei Ye]

I really want this for the AF microadjust (my lenses are really annoying me with front focusing)and FF sensor, but I'll wait for Bryan's review and DPR's reviews first