canon rumors FORUM

Rumors => Lenses => Topic started by: Canon Rumors on September 27, 2010, 01:19:50 PM

Title: EF 24-70 f/2.8L Replacement [CR2]
Post by: Canon Rumors on September 27, 2010, 01:19:50 PM

Stop teasing me!

I know, I know. We keep talking about it and nothing happens. 99% of the stuff that comes in regarding this lens I put to the side.


However, a great source has finally spoken up in regards to a replacement. I’m not putting CR3 on it because I don’t have a specific date.


What I am told is the lens is coming “sooner rather than later”. There’s 2 possible announcement dates.


It sounds like it will be launched alone like the EF 70-200 f/2.8L IS II was. It’ll either be announced before the end of the year, OR just before WPPI which starts February 17, 2011.


It’s not confirmed it’s going to be an IS lens, though if it wasn’t. I’d be completely shocked.


This is officially the best confirmation I’ve received in regards to this lens.


You will know more the second I know more.


cr


Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: leptonsoup337 on September 27, 2010, 01:57:31 PM
I look forward to the specs on this lens...
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: weaponOfchoice on September 27, 2010, 03:24:52 PM
I was just about to pull the trigger on getting the "old" one...
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: AlleyB on September 27, 2010, 03:47:32 PM
I am dying for this one...  C'mon Canon!!
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Son of Daguerre on September 27, 2010, 03:54:42 PM
Better have IS... I've got shaky hands.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Etienne on September 27, 2010, 04:11:03 PM
This ain't gonna happen but, i wish they'd make it lighter and smaller, even if it was only 24-50, or 35-85, 2.8L IS
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Justin on September 27, 2010, 04:22:25 PM
Maybe an early Jan launch like the 70-200 then. How about a 14-24?

<p><strong>Stop teasing me!<br />

<span style=\"font-weight: normal;\">I know, I know. We keep talking about it and nothing happens. 99% of the stuff that comes in regarding this lens I put to the side.</span></strong></p>
<p>However, a great source has finally spoken up in regards to a replacement. I’m not putting CR3 on it because I don’t have a specific date.</p>
<p>What I am told is the lens is coming “sooner rather than later”. There’s 2 possible announcement dates.</p>
<p>It sounds like it will be launched alone like the EF 70-200 f/2.8L IS II was. It’ll either be announced before the end of the year, OR just before <a href=\"http://www.wppionline.com/\">WPPI which starts February 17, 2011</a>.</p>
<p>It’s not confirmed it’s going to be an IS lens, though if it wasn’t. I’d be completely shocked.</p>
<p>This is officially the best confirmation I’ve received in regards to this lens.</p>
<p>You will know more the second I know more.</p>
<p><strong><span style=\"color: #ff0000;\">c</span>r</strong></p>

Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: traveller on September 27, 2010, 05:59:52 PM
Strange, the price of the 24-70mm L seems to be falling recently in the UK (though this could simply be exchange rate fluctuations).  Warehouse Express are showing it on backorder (disclaimer #2: as they are with all of Canon's non-L wideangle primes and the 50mm L)...

Come to think of it, this probably means sweet F.A.  :)

Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: scalesusa on September 27, 2010, 07:21:47 PM
After waiting for some improved lenses, I have started collecting primes.  I can take just one or two on most shoots and find that I like the wider apertures better.  I bought the 70-200mm f/2.8 MKII and sent it back when I realized that I just preferred the primes.  I suppose it will be the same with the 24-70, but I'll probably try it anyway.  I went thru five of the current lenses. and none impressed me.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: off topic on September 28, 2010, 12:56:34 AM
If the sensors are going to increase in pixels (30+) the 24-70 is going to need to do a lot more resolving.

IS seems essential if canon is interested in selling this lens to the DSLR video shooters. I also saw an interview stating that the new big white lenses have new special motors for running prepragammed focus pulls but none of the current bodies have the controls to use this function. Which leads me to wild speculation, what about canon adding a motorized zoom to the 24-70? This would not help shave any weight off what is currently a 2lb lens.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: macfly on September 28, 2010, 03:31:30 AM
It certainly seems as though there is a place for Canon to go with its still glass that would take it closer to its cine glass, and that would take it closer to competing with the next gen Reds and the H3/H4 etc medium formats. This will certainly be the next major step up for those of us shooting for a living, with more and more clients demanding streaming content.  I've gathered that most folks here seem not to be too concerned with working gear, but since I work with mine that is what I'm most interested in.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Maldical on September 28, 2010, 09:00:24 AM
I'd be excited if it cost the same as the existing one.  I know this will probably sell at $2K so no go for me.  :(
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Justin on September 28, 2010, 09:45:26 AM
 There are other working folks here.  :) I take your point that Canon has stopped making still photo only dslrs, yet they keep making lenses omtimized for stills. Maybe another line of lens would do, but it seems to me hybrids like you suggest would be a good strategy for most users, weight concerns aside.

:)
It certainly seems as though there is a place for Canon to go with its still glass that would take it closer to its cine glass, and that would take it closer to competing with the next gen Reds and the H3/H4 etc medium formats. This will certainly be the next major step up for those of us shooting for a living, with more and more clients demanding streaming content.  I've gathered that most folks here seem not to be too concerned with working gear, but since I work with mine that is what I'm most interested in.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: CameraAddict on September 28, 2010, 12:28:35 PM
With any luck the ergonomics and sharpness will be at least as good as the Nikon lens.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: dmisita on September 28, 2010, 11:33:39 PM
It seems to me that a hybrid is typically a compromise at best.  It is my guess that they will eventually create a line of cine-optimized SLR lenses, and will just expect you to swap them out.   After all, it's not exactly outside the SLR users experience to swap lenses depending upon the needs of the situation.

If the concept cameras are anything to go by, we're all going to be shooting with a big ole' video camera and capturing our stills off of that anyway . . .

Personally, I'd just like to see a replacement with equal or improved IQ, and IS thrown in for good measure.  I, too, was just about to pull the trigger on the current model . . .

There are other working folks here.  :) I take your point that Canon has stopped making still photo only dslrs, yet they keep making lenses omtimized for stills. Maybe another line of lens would do, but it seems to me hybrids like you suggest would be a good strategy for most users, weight concerns aside.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Richard on September 29, 2010, 08:22:22 PM
I shutter to think of the price this will command. With the change in the exchange rate in the US Dollar vs. Yen, we are in for some sticker shock. My guess is we will be HAPPY for this to come in under 2K. Can't blame Canon, since they get profits in the end as Yen, and math is math. 
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Justin on September 30, 2010, 10:56:19 AM
I hear you but if it is stellar optic it will maintain its value well and will last for years and years. I don't mind paying 50% more for a lens that is 50% better. I think it's fair.

I shutter to think of the price this will command. With the change in the exchange rate in the US Dollar vs. Yen, we are in for some sticker shock. My guess is we will be HAPPY for this to come in under 2K. Can't blame Canon, since they get profits in the end as Yen, and math is math.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: pgabor on September 30, 2010, 04:55:15 PM
I hear you but if it is stellar optic it will maintain its value well and will last for years and years. I don't mind paying 50% more for a lens that is 50% better. I think it's fair.

+1
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: RogerC on September 30, 2010, 06:24:54 PM
This lens will be expensive. Canon has to make it very attractive to justify a purchase or upgrade. To a lot of people this lens is already perfectly adequate. So one asks what is it that is going to be the deal maker?
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: lotus on September 30, 2010, 08:31:16 PM
CR Guy

Any word or estimates of when the October rebates on Canon Gear will kick in? It has been 22,19,18 Oct in the past. Can we expect something similar?

I am thinking I can save some money on a 7D and some older L Lens.

Thanks!  8)

Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: ablearcher on October 04, 2010, 11:37:41 AM
I might consider the new one for outdoor location shoots. However, at this point I prefer primes for low light and better background blur (and a better IQ in general). Also, 24-70 feels kinda short for studio work (I'm happy I went with 24-105L for that). But 24-70 will work well with 70-200 for weddings and location shoots on two bodies with good light...
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Justin on October 04, 2010, 06:53:48 PM
I have to say I am tired of waiting for this lens. I sold my aps-c camera for a 5D2 almost a year ago and had to sell my 17-55 2.8 IS, my favorite lens. At the time I expected that a 24-70 was imminent. Anyone would who followed camera rumors for a few years. Sure I was excited when the 70-200 2.8 successor was launched. Yes I shoot with it all the time, but I find myself making compromises all the time too. I pack the 35 1.4 but only get a clean shot with very careful setup and at anything under 2.8 it's not tack sharp. I have a 24-105 but it leaves something to be desired due to narrow max aperture. Maybe the thing to do is go buy a 7D or a 60D and get the 17-55 back. I really miss this range. I don't want to be without an image stabilized zoom lens any longer. Come on Canon. Release this lens already.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 04, 2010, 08:15:06 PM
I sold my aps-c camera for a 5D2 almost a year ago and had to sell my 17-55 2.8 IS, my favorite lens.

The 17-55/2.8 IS lens on APS-C @ iso 100 corresponds to 27-88/4.5 on FF @ iso 160 (same exposure, same depth of field, same photon noise), so if you were content with that lens I see no reason you would be less happy with 24-105/4L IS on 5d2.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Justin on October 05, 2010, 09:47:15 AM
I understand your point, but the qualities of these lenses are not equivalent. In terms of sharpness, I have to stop down to f11 on the 24-105 at 70mm to get even close to the 17-55 at the long end. So in other words, and to be fair because I didn't put it in my earlier comment, the wider maximum aperture is not he only thing I am looking for in a standard zoom lens. Yes I want 2.8, because as you suggest it produces very narrow DOF on a full frame camera. But I am looking for a sharp optic as well, in addition to contrasty, punchy, low CAs, minimal distortion, fast focusing output. 

I sold my aps-c camera for a 5D2 almost a year ago and had to sell my 17-55 2.8 IS, my favorite lens.

The 17-55/2.8 IS lens on APS-C @ iso 100 corresponds to 27-88/4.5 on FF @ iso 160 (same exposure, same depth of field, same photon noise), so if you were content with that lens I see no reason you would be less happy with 24-105/4L IS on 5d2.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 05, 2010, 05:06:33 PM
In terms of sharpness, I have to stop down to f11 on the 24-105 at 70mm to get even close to the 17-55 at the long end.

That is surprising, I haven't seen complaints on the sharpness of the 24-105/4L IS before (most complaints are about the strong barrel distortion at 24mm). Perhaps you have a bad copy/AF problems? According to MTF measurements by photozone.de, the 24-105/4L on 5D2 should be slightly sharper than 17-55/2.8 on 50D (although the latter is better than 24-105/4L on 50D; this is because of the APS-C 1.6x center resolution disadvantage compared to FF). It also seems the 24-105/4L is at its worst in the corners at 70mm (but still better than 17-55/2.8 at 55mm).

But yes, I'm very fond of my 17-55/2.8 IS lens and, just as you, I'm waiting for a normal F/2.8 zoom with IS to switch to FF (e.g., 24-70/2.8L IS). Even with a good calibrated copy, merely doing "slightly better" is not big enough incentive for me to switch.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 11, 2010, 07:24:42 PM
Just FYI Justin, I got access to exactly your setup (5D2+24-105/4L) and took the opportunity to compare it to my 7D+17-55/2.8. Tripod, no IS, with a boring bookshelf as the subject. Manual focusing of centre with live view, remote shutter release with mirror lock up. Focal plane parallel to bookshelf. 24-105/4L @ 70mm (supposedly its worst focal length), 17-55/2.8 @ 44mm (the equivalent). iso 160 and 1s exposure for 5D2, iso 100 and 1s exposure for 7D (gives the same exposure level).

Result: Sharpness about equal in corners, 24-105/4L better in centre.

Then I stepped down the aperture 2 steps (i.e. to 8.0 and 5.6, respectively) and increased exposure time to 4s.

Result: 24-105/4L@8.0 improved corners significantly, and center somewhat, clearly out-resolving the 17-55/2.8@5.6, which didn't improve as much compared to wide open.

Conclusion: The resolution of the 5D2+24-105/4L is no worse than 7D+17-55/2.8, so have no remorse for selling your EF-S lens.

(NB, I can't guarantee that my results are typical, maybe I received a good 24-105/4L copy and a poor 17-55/2.8, but what I find is in line with expectations from MTF measurements)

If you're interested I can find a way to post relevant crops of the images.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: neuroanatomist on October 12, 2010, 08:26:56 AM
But yes, I'm very fond of my 17-55/2.8 IS lens and, just as you, I'm waiting for a normal F/2.8 zoom with IS to switch to FF (e.g., 24-70/2.8L IS).

I also really like my EF-S 17-55mm f/2.8 IS.  But, keep in mind that with the difference between a 1.6x and FF sensor, the 24-105mm f/4L IS actually specs out better on FF than the 17-55mm on 1.6x crop.  With the crop factor applied to aperture (as it does in terms of DoF for the same framing), the FF equivalent of the 17-55mm f/2.8 is 27-88mm f/4.5, so you can see that the 24-105mm f/4 on FF is 3mm wider, 17mm longer, and 1/3-stop faster.  Granted, shutter speed is faster with f/2.8, but since the ISO performance is also improved by 1.33 stops on FF vs. crop, you can get equivalent noise performance and bump to a higher ISO on FF f/4 to maintain the shutter speed you'd have on crop at f/2.8.

So, bottom line, if you are waiting for a 24-70mm f/2.8L IS because you want a FF-equivalent of your 17-55mm IS, you can have that right now as the 24-105mm f/4L IS.   
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 12, 2010, 05:00:46 PM
While the effective field of view on a crop camera may be the same as a longer lens on a 35mm, the focal length does not change and therefore neither does the aperture.  A 17 - 55mm lens may give the same FOV as a 27 -88mm but it's still a 17 - 55mm and the relationship between the first element and the focal length remains unchanged as does the aperture.

Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Macadameane on October 12, 2010, 05:19:56 PM
While the effective field of view on a crop camera may be the same as a longer lens on a 35mm, the focal length does not change and therefore neither does the aperture.  A 17 - 55mm lens may give the same FOV as a 27 -88mm but it's still a 17 - 55mm and the relationship between the first element and the focal length remains unchanged as does the aperture.

You are right, but a FF camera also utilizes more overall light and is more suited for low-light photography and video shooting.  Depth of field also can become thinner on a full frame.  I don't know the technicalities, though, does someone want to shed some light?  It probably is a matter of pixel size and spacing rather than "light gathering".
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 12, 2010, 05:37:51 PM
DOF becomes less because in filling the frame for a portrait the magnification increases therefore lessening the DOF.

In terms of FF working better in lower light the issue is not as simple as some would have us believe, put simply bigger pixel sites.  Unfortunately a larger site does not mean a larger sensitive area or pixel, and then there is the isolation of one pixel from the next which is the cause of some noise.  It is possible to have a large sensor with a small number of MP which is worse in low light than a small one with a higher pixel density.

However if you imagine a light source with a constant brightness (white) a lens with a given aperture will project uniform brightness over all the sensor, hence there is no difference between a FF camera and a crop one.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 12, 2010, 06:09:31 PM
So, bottom line, if you are waiting for a 24-70mm f/2.8L IS because you want a FF-equivalent of your 17-55mm IS, you can have that right now as the 24-105mm f/4L IS.

You're right, and that was exactly my point :) Jason was complaining that his 24-105/4L wasn't as good on his 5D2 as his 17-55/2.8 had been on his 50D, and I was surprised, because I thought the 24-105/4L would be similar but slightly better, if anything. I then went on and tested a 17-55/2.8  on a 7D and a  24-105/4L on a 5D2, and found that the latter was indeed very similar, but slightly better performer (for my copies).

But the bottom line is that I do not find slightly better compelling enough to go FF. A good 24-70mm f/2.8L IS on the other hand would convert me in an instant.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 12, 2010, 06:41:37 PM
While the effective field of view on a crop camera may be the same as a longer lens on a 35mm, the focal length does not change and therefore neither does the aperture.  A 17 - 55mm lens may give the same FOV as a 27 -88mm but it's still a 17 - 55mm and the relationship between the first element and the focal length remains unchanged as does the aperture.

You're right, but what is your point? The focal length just gives the image scale. 50mm/2.8 on FF gives exactly the same field (solid angle) as 80mm/4.5 on 1.6x APS-C (barring lens distortion). The flux of incoming photons per solid angle will be the same. The DOF will be the same. If the detectors have the same number of pixels with the same sensitivity (say fraction of photons actually detected, also called quantum efficiency) and read-out noise, dark current etc, then the resulting image will be statistically identical in all respects.

The lens is just an optical system to capture photons and compress them to a small image. The advantage of FF sensors is not that they are inherently more sensitive. The advantage is that it's easier to make optics that produce larger image scales (e.g., it's easier to produce a good EF 80mm/1.2 lens than an EF-S 50mm/0.75 lens).
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 12, 2010, 06:57:56 PM
[You're right, but what is your point? The focal length just gives the image scale. 50mm/2.8 on FF gives exactly the same field (solid angle) as 80mm/4.5 on 1.6x APS-C (barring lens distortion).

The point was in response to the previous post!
aperture does not affect FOV, as you appear to be quoting however, and f/2.8 is important on Canon cameras because of the more sensitive focus centre spot.

Perhaps you would explain the change in focal length in the wrong direction?  50mm on FF is the same FOV as a 30mm (nearest equivalent) on a 1.6 crop, the aperture values would not change, DOF might depending on conditions
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 12, 2010, 07:46:24 PM
Perhaps you would explain the change in focal length in the wrong direction?  50mm on FF is the same FOV as a 30mm (nearest equivalent) on a 1.6 crop, the aperture values would not change, DOF might depending on conditions

I don't think I understand. Yes, 50mm on FF shows approximately the same field as 30mm on 1.6x APS-C. You didn't state the aperture values, so I don't know what you mean when you write that they don't change. In relation to what? Focal length and aperture (as in entrance pupil) are independent quantities, and the f-number is their ratio.

Let's put it this (trivial) way. 50mm/2.8 on 1.6x APS-C is exactly the same as 50mm/2.8 on FF, where only the central 1/1.6 = 62.5% (in linear dimension) of the frame is used.

With shorter focal length, you compress solid angle onto a smaller part of the detector; so with 31.25mm you compress the same field on the APS-C as the 50mm does on the FF. If we assume that the entrance pupil is the same, that is, the same number of photons per solid angle is captured for both lenses, then that implies that the photon density at the detector must be higher for the 30mm lens (because the same number of photons were compressed onto a 1.6^2 smaller area). That is, the f-number is sqrt(1.6^2) = 1.6 smaller.

I'm sorry if my explanations are confusing, I'm sure there is a good web page somewhere which explains things better.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 13, 2010, 03:13:56 AM
Unfortunately that's not so epsiloneri, you're counting the crop factor twice.
the final element of a 50mm f2.8 is 18mm on a 30mm 11mm (rounded out), but the ratio between these two is 1.6 (surprise!).  If you then make allowance for the crop in a further calculation you count it twicw which makes the result wrong.

f/2.8 is a constant regardless of the focal length if the lens is pointed at a uniform light source the light reaching the sensor should be constant across its surface.  Therefore the size of the sensor is unimiportant, as is the crop factor.  A slightly more meaningful figure would be to use the pixel density, but even then as sensors peform differently it's difficult to make the test accurate enough to make any sense.

A FF camera and a crop camera pointed at the uniform light source with say a 50mm & 30mm both at f/2.8 and the same ISO should return the same shutter speed for correct exposure.

Just to make it more complicated though, not all cameras share the same bayer matrix, they can be stronger or weaker, then there's the anti aliasing filter, and they're not all the same either, not the microlenses.  It's very difficult to compare like with like.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 13, 2010, 04:46:24 AM
Unfortunately that's not so epsiloneri, you're counting the crop factor twice.

Thanks for your comment, but you're not being very clear. What is not so? Please be very precise and refer to the exact statement you don't agree with, otherwise I have no hope in following you.

So you don't agree that 50mm/2.8 on a FF is identical to 31.25mm/1.75 on 1.6 APS-C? Or is it something else?

Just to make it more complicated though, not all cameras share the same bayer matrix, they can be stronger or weaker, then there's the anti aliasing filter, and they're not all the same either, not the microlenses.  It's very difficult to compare like with like.

Yes, there are other effects, but they are less significant by comparison ("second order corrections") and more about engineering than fundamental physics.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 13, 2010, 05:09:35 AM
So you don't agree that 50mm/2.8 on a FF is identical to 31.25mm/1.75 on 1.6 APS-C? Or is it something else?

Yes I don't agree with that, f/2.8 is f/2.8 regardless of the crop factor
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 13, 2010, 05:23:37 AM
So you don't agree that 50mm/2.8 on a FF is identical to 31.25mm/1.75 on 1.6 APS-C? Or is it something else?

Yes I don't agree with that, f/2.8 is f/2.8 regardless of the crop factor

Ok, good, then I understand. You are right, that for the same lens the aperture doesn't change when you go from FF to crop. That would be weird. But now think of two different lenses that both share the same entrance pupil - say 18mm in both cases - but where the focal length is different, namely 50mm in one case and 31.25mm in the other. Then the image on a FF with the 50mm lens would be identical to the image of the 31.25mm on the 1.6x APS-C. And, also note, since the entrance pupil is the same, the f/#-number changes: 50/18 = 2.8 while 30/18 = 1.75. Which is what I stated in the quote above.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: neuroanatomist on October 13, 2010, 05:48:08 AM
While the effective field of view on a crop camera may be the same as a longer lens on a 35mm, the focal length does not change and therefore neither does the aperture.  A 17 - 55mm lens may give the same FOV as a 27 -88mm but it's still a 17 - 55mm and the relationship between the first element and the focal length remains unchanged as does the aperture.

True.  But not really the point I am making...  55mm on a crop body is equivalent to 88mm on FF, and f/2.8 is f/2.8 regardless.  But for the same framing, you'd be closer to the subject with a FF body, meaning shallower DoF.  It also means the perspective is different, so it's not really the same shot.  But from a technical standpoint, on FF DoF is effectively shallower, and when comparing current FF sensors to current crop sensors, ISO performance is improved so one can increase ISO by a stop to 'make up the difference' between f/2.8 and f/4 (in terms of shutter speed) with no noise penalty. 

What that means, and my main point, is that functionally the 24-105mm f/4 on FF is approximately equivalent to the 17-55mm f/2.8 on a crop body (from a DoF and exposure standpoint, plus it has a broader focal range).  So the "I'm not going FF yet because there's no FF equivalent to the 17-55mm f/2.8 IS" argument is a fallacy, since on FF, f/4 + better ISO performance is comparable to 1.6x f/2.8, and both lenses have IS. 

Now, if someone is waiting for f/2.8 IS on FF because the whole point of moving to FF is to achieve better performance, rather than comparable performance (from a technical standpoint), I can't argue with that - so, if that's the case, keep on waiting for the 24-70mm f/2.8L IS. 
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: Flake on October 13, 2010, 08:08:47 AM
One of the problems is that f/2.8 is a magic number for Canon cameras and gives a brighter viewfinder, and more accurate autofocus.
The current f/2.8 24 -70mm is a far better lens than the 24 - 105mm f/4 IS and I'm speaking from experience owning both of them, just sold the f/2.8 in anticipation of a new one before values fall.
Photozones test of the 24 - 105mm f/4 IS on FF wasn't what I wanted to see, it has problems with edge softness vignetting, distortion, and its minimum focus distance and magnification leave a lot to be desired.  It's useless for close up work, the 17 - 55mm is much closer to the 24 - 70mm here.
The saving grace of the 24 - 105mm is the IS which the 24 - 70mm doesn't have, when it finally gets it I think the 24 - 105mm will be going on Ebay!
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: neuroanatomist on October 13, 2010, 09:52:44 AM
So you don't agree that 50mm/2.8 on a FF is identical to 31.25mm/1.75 on 1.6 APS-C? Or is it something else?

Yes I don't agree with that, f/2.8 is f/2.8 regardless of the crop factor

Ok, good, then I understand. You are right, that for the same lens the aperture doesn't change when you go from FF to crop. That would be weird. But now think of two different lenses that both share the same entrance pupil - say 18mm in both cases - but where the focal length is different, namely 50mm in one case and 31.25mm in the other.

Yes, f/2.8 is f/2.8 and the light per unit area of the sensor is the same, independent of sensor size.  Likewise, the focal length of a lens doesn't change on crop vs. FF, just the angle of view (i.e. the magnification is the same).  The effect on DoF is an apparent one, seen in practice, even with the same lens.  If I frame a head shot with an 85mm f/1.2 @ f/1.2 on my 7D, then I say 'whoops, what am I thinking' and move the 85/1.2 onto a 5DII without moving my feet or the subject, instead of a nice, tight head shot I'll have a lot of background around the subject.  So, I'll take a few steps forward to get that nice tight framing again, and that decreased distance-to-subject translates to a shallower DoF - by a factor of 1.6x.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: neuroanatomist on October 13, 2010, 09:57:30 AM
The saving grace of the 24 - 105mm is the IS which the 24 - 70mm doesn't have, when it finally gets it I think the 24 - 105mm will be going on Ebay!

With this, I agree.  If Canon ever gets around to releasing the 24-70mm f/2.8L IS, my 24-105mm f/4L IS will go on the auction block...
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 13, 2010, 02:30:59 PM
Photozones test of the 24 - 105mm f/4 IS on FF wasn't what I wanted to see, it has problems with edge softness vignetting, distortion, and its minimum focus distance and magnification leave a lot to be desired.  It's useless for close up work, the 17 - 55mm is much closer to the 24 - 70mm here.

As I already wrote, according to the photozone tests themselves, 24-105mm/4.0L on 5D2 is at least as good as 17-55mm/2.8 on 7D, at least if we're talking IQ (7D has other advantages). I confirmed it with my own tests. In other words, the 17-55mm/2.8 on 7D is just as useless as 24-105mm/4.0L on 5D2.

f/2.8 on APS-C gives about the same viewfinder brightness as f/4.5 on FF. Why is that? Because in order to view the full field of view in the same solid angle, the FF viewfinder needs to compress the image (almost) 1.6x more than the APS-C viewfinder -> increasing the surface brightness. This is easy to test yourself: mount the 17-55/f2.8 on a 7D and the 24-105/4L on a 5D2. Which viewfinder is brightest? They're about the same (the 5D2 has a slightly larger apparent field in the viewfinder, but it's compensated by the lens being 4.0 instead of 4.5). If you don't believe me try it! (Of course, your 24-70mm/2.8L lens will be much brighter on the 5D2.)
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: epsiloneri on October 13, 2010, 02:42:13 PM
So, I'll take a few steps forward to get that nice tight framing again, and that decreased distance-to-subject translates to a shallower DoF - by a factor of 1.6x.

Yes, but the perspective will have all changed, so it's not equivalent. I think we both agree that, in contrast, the imaged formed by a 50mm/2.8 lens on a FF sensor is actually equivalent to the image formed by a 31.25mm/1.75 lens on a 1.6x APS-C sensor. Actually equivalent (identical!), in terms field of view, photon collection rate per solid angle, depth of field. No difference.
Title: Re: EF 24-70 f/2.8L Replacement [CR2]
Post by: kubelik on October 19, 2010, 07:10:04 AM
dilbert, the guys over at luminous landscape would have to disagree:

http://www.luminous-landscape.com/reviews/lenses/24-70-review.shtml

at least to me, I value the opinion of actual in-the-field shooters a heck of a lot more than I value DXOmark scores, which, to put it politely, I consider a bunch of hogwash