What exactly is it that you could do with the 17-55 that you can't with the 24-105? The 24-105 on a full frame body is wider at the wide end and longer at the long end than the 17-55 on a 1.6 fovcf body. It is also faster: f/4 on a full frame body is like f/2.5 on a 1.6 fovcf body, both in terms of dof and light gathering.
Jon,
I don't thinkits true tosay it is faster. I agree with the DOF comment. But f4 is f4. Full frame has better high iso, but thats not the same thing.
Tom
To me it seems to be exactly the same thing. If sensor 1 is twice as big as sensor 2, iso 800 on sensor 1 has the same noise as iso 400 on sensor 2. So you can get the same shutter speed with the same noise with f/4 on the bigger sensor as f/2.8 on the smaller sensor.
You could say, "well, the difference is the sensor, not the lens. F/4 is f/4." But if the f/2.8 lens can't illuminate the bigger sensor, I think the terminology is appropriate. The 24-105 lens is actually capable of getting more light onto a ccd at f/4 than the 17-55 is at f/2.8. Similarly, I would call an f/4 medium format lens faster than an f/2.8 35mm one, because the medium format lens gets more light to the sensor (or film).
That's just terminology, though, and if you think I am crazy for using the word "faster" that is coolMy main point is that I don't see any major disadvantage of the 24-105 f/4 on a full frame as compared to 17-55 f/2.8 on a 1.6 fovcf camera.
Adding IS to the 24-70 f/2.8 is a very common request and I'm sure that Canon has heard a lot about it, but personally, IS doesn't interest me that much at that focal length. My subjects usually need 1/60 or faster, and I can handhold 1/60 at 70mm even on the 5D2. Of course, there's an entire world of subjects that would benefit greatly from it; however, my understanding is that IS is not quite as effective at short focal lengths. (I hear less than 2 stops improvement at 24mm on the 24-105.) Right now my preferred lenses are 24mm f/1.4, 50mm f/1.4, and 70-200 f/4 IS, so I don't even use a typical "walkaround zoom".
I agree with John Ruyle and Tom Alicoate: the 24-105 f/4 IS has a wider aperture and more light gathering power than the 17-55 f/2.8. The only thing that it doesn't do as well is activate the f/2.8-only autofocus sensors.Originally Posted by atticusdsf
I posted about this topic here:
http://community.the-digital-picture.../42/94.aspx#94
The 24-105 has a *wider* aperture than the 17-55 at every equivalent field of view and perspective. For example, the aperture on the 17mm at f/2.8 is 6mm. The L at 27mm f/4 is 7mm: 17% wider aperture. The larger front element of the L points toward this fact too.
The focal ratio (not aperture) is one stop narrower (f/4 vs f/2.8), so the light intensity per area is twice as dim. However, the total amount of light is more than double, thanks to the much larger area and wider aperture. So you can up the ISO or use -1 EC to get the same shutter speed as with f/2.8 and still collect a half-stop more light in total. The resulting image will be superior to the 17mm on the 30D, and only slightly better than on the 50D.
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.
There is one web page that explains all of this, and more, in excrutiating detail.
http://www.josephjamesphotography.com/equivalence/
Yes please .... I want one.
The 24-70 is most probably my most used lens. I use it especially indoors (churches etc) and would love IS.
It isn't that a 24-70 is wouldn't be great. It would be.
But the two lenses I would most like to have with IS are the 100mm macro and the 135mm f/2.
Macro because you never have enough light for macro, it seems, since one is always stopping down to very large effective f/ numbers, and because one often does a lot of cropping. And it isn't always convenient or possible to follow a bee or butterfly or whatever through the bushes with a tripod. Yes, you can use flash, but sometimes one wants natural light. Am I the only one that has this problem? I've taken to using my 70-200 IS with extension tubes at times for butterflies.
And the 135 f/2 because, even at f/2, the thing isn't that hand-holdable in low light due to the long fl. A 4-stop IS would be huge.
do you think canon will eventually make it though? I have a 1.6 crop camera and eventually want to upgrade to full frame, just worried about if i buy 17-55 for now to satisfy my current need i'll regret when 24-70 f2.8 comes out... if it does ...
you are where i was a year ago.. however i decided that the wide angle was important enough to me that i'd go ahead and get the 17-55.
i still don't regret it.. i upgraded to a 5dmkII, but i'm still keeping my old camera because it's good to have a backup, and the 17-55 is a great lens to just leave on that camera.
Current price of the EF 24-70 is arround 1200EURO with IS it would probably cost 1800EURO...
IfCanon makes a zoom wide angle/tele f2.8 L IS USM I'll buy it and a full frame camera on the next day. Serious.
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