17-55 ef-s + 24-105, or 24-70 2.8?

[Kayaker72]

I am actually working on deciding if it is worth keeping my 7D after upgrading to FF (5DIII) as well. I had planned on selling the 7D, but, at least for now, I am keeping the 7D. If what happened to Neuro happens to me, namely that the 7D isn't used, then it will be sold in a couple of months. The issue is that I often crop the images I take with the 7D. So, while all the above is true if you crop the 6D down to the 7D FoV, I will likely be cropping well beyond the 7D FoV for subjects, usually birds, but sometimes other subjects.

I posted the comparison of the 5DIII with the 100-400 L @ 400 mm with and without the 1.4 TC here. I took the same shots at the same time with the 7D. These shots were ~1:1 of the 5DIII image, so the 7D has some extra pixels. The 5DIII definitely was a "cleaner" image at even moderate ISO (400/800), as mentioned, but there is more detail to the shots I took with the 7D at ISO 100. Two quick examples (manual focus with live view; increased sharpening in post):
Tree at ~100 ft/30 m:
5DIII:

5DIII LR4 900 600-0092-2 by kayaker72, on Flickr

7D:

7D LR4 900 600-2203 by kayaker72, on Flickr

Tree at ~150 ft/45m:
5DIII:

5DIII LR4 900 600-0097 by kayaker72, on Flickr

7D:

7D LR4 900 600-2200 by kayaker72, on Flickr

First, let me say that I think the 5DIII is remarkably close to the 7D in this pixel peeping test. So there is definitely something to the pixel quality vs pixel quantity argument. The images are close enough, and this is an extreme enough crop, that the difference may not be noticeable in real world use. But, as there is more detail to the 7D shots and I am often cropping shots taken from my 7D, I decided to hold onto the 7D and let the real test will be when I am out shooting wildlife.

BTW, I am very impressed by the 5DIII thus far. Most of my shots are around the house (low light/high ISO). But it gets focus in low light where the 7D would just hunt and the noise performance is great.

Also, just to show how extreme of a crop this is, below is a similar full size image of the first (100 ft) tree (crop taken out of the center).

5DIII 900 600-0091 by kayaker72, on Flickr

[Kayaker72]

Looking for opinions- Currently have a 7D with the 17-55 2.8 EF-S lens, which I love. Didn't think I'd upgrade to full frame anytime soon, but the 6D is looking good, particularly for its low-light capabilities. I shoot mainly low light situations like concerts. So 2.8 is really about the slowest I can use for a lot of shows.
It seems a no-brainer to get the 6D bundled with the 24-105. Trying to decide if I should keep both lenses, and carry two bodies at shows, with fast primes on the 6D and the 17-55 on the 7D. OR sell both and buy the 24-70 2.8 (original). I think the 2.8 might be more important than IS. Anyone of experience with all these lenses?
Thanks!

More of a direct response to the original post, the focusing in low light of the 5DIII is much better than the 7D. Really, it is often the difference of getting focus in low light versus not getting focus in low light. And the 6D is supposed to be even better than the 5DIII in low light focusing (EV -3 sensitive vs EV -2 at the center point). Popular photography timed the 5DIII AF at EV -2 at 1.15 secs. I saw that the 6D review is on newstands, but it isn't online yet.

I have noticed better low light focusing on my 5DIII with the 50 f/1.4 compared to the 24-105 f/4. I assume this is because it activates the f/2.8 senstive AF points (I haven't checked the lists yet). So, if you already have the fast primes, I might go with that. Otherwise, I would probably be selling both lenses and getting f/2.8 (or better) glass on the 6D for your low light situations.

ISO performance will be the other thing that really impresses you. There is a thread over at CR posting high ISO photos taken with the 5DIII. If you believe DXO, the 6D should even be a bit better. From what I've seen, there is a 2-3 stop improvement over the 7D. I can clean up ISO 6400 images and I am beginning to think I can use ISO 12,800 images.

[gbc]

Thanks for the comparison shots. I'm definitely going to hang onto the 7D at least for a while for comparison. I also crop my 300mm shots quite a bit, especially birds in flight, and far away concert shots. So I'll be interested to see how they compare to the 6D shots.

[thekingb]

I recently upgraded to a 6D and have the 24-105 mounted. I am blown away by what I can capture in low light with an f/4 lens compared to the 7D. It's like I skipped many generations of technology.

But I am definitely keeping the 7D for now for those situations where I need AI servo mode. The 7D is still better in that department. It's also a bit more rugged.

[DavidEccleston]

Thanks for the mentions of AI servo on the 6D. I was hoping I could sell everything and get a 6D, but it looks like I'll have to wait for the 5DmkIII to have a massive price drop.

[gbc]

Is AI Servo mode that much worse on the 6D than the 7D? I'd say at least half my photography is concert shots, where there's usually low light or strobes or other quick and extreme lighting changes, and where the subjects tend to move around unpredictably. So the low-light capabilities are the main appeal of the 6D, but if the AF isn't great, especially at the non-center points, I'm starting to think I may be better off sticking with the 7D and waiting for a price drop on the 5D3. Though that leaves me without a general purpose zoom lens.

[neuroanatomist]

AI Servo attempts to predictively track subject movement. That is facilitated by having more AF points and/or more densely-packed AF points. The 5DIII/1D X are much better in that regard than the 6D, and the 7D is better as well.

[Kayaker72]

The current deal on a refurbished 5DIII is among the best I have seens since the 5DIII was released:

http://shop.usa.canon.com/webapp/wcs....mc_id=C126149

[gbc]

OK, finally got the 5DMIII. Now looking for the general purpose lens. As mentioned before, was using the 17-55 2.8 on the 7d. Considering the 24-105 now. I've read on a few forums that the f4 on the 5DMIII will be better or just as good in low light as the f2.8 on the crop sensor. Is this true? I'm pretty happy with the low light performance I've been getting with the 17-55/7D combo, so if I can get something close to that with the 24-100 without having to splurge for the 24-70 II (or the Tamron 24-70), I'd be satisfied with that.
Though I WILL be selling the 7D and 17-55...

[Busted Knuckles]

OK, finally got the 5DMIII. Now looking for the general purpose lens. As mentioned before, was using the 17-55 2.8 on the 7d. Considering the 24-105 now. I've read on a few forums that the f4 on the 5DMIII will be better or just as good in low light as the f2.8 on the crop sensor. Is this true? I'm pretty happy with the low light performance I've been getting with the 17-55/7D combo, so if I can get something close to that with the 24-100 without having to splurge for the 24-70 II (or the Tamron 24-70), I'd be satisfied with that.
Though I WILL be selling the 7D and 17-55...

I have the 24-105 on the 5dIII and am generally pleased... but.... I picked up the 40 2.8 pancake and it really points out how soft the corners of the 24-105 actually are.

I am toying with the idea of the 24-70 2.8 or perhaps going to primes - w/ the low light performance of the 5dIII it is an interesting question.