Technical Question on Lens Sharpness 24-70 v. 200m

[dwdallam]

I shot the same object, a tree trunk, at relatively the same lens length, but using different lenses.

Canon 24-70 L @ 2.8 at 67mm
Canon 70-200 L @ 2.8 at 75mm

The 70-200 produced a very noticeably sharper image. I shot 30 images with the 24-70 and never matched the 70-200 in sharpness, not only at the focal point, but also as the image radiates outward on the trunk.  When I used f10 on the 24-70, I matched the 70-200 @ f2.8 in sharpness. But the 200 was shot at 2.8, not f10!

What's going on here? I thought for sure the 24-70 would deliver a sharper image hands down than the bigger lens just due light having to pass through more glass.

[francois]

I shot the same object, a tree trunk, at relatively the same lens length, but using different lenses.

Canon 24-70 L @ 2.8 at 67mm
Canon 70-200 L @ 2.8 at 75mm

The 70-200 produced a very noticeably sharper image. I shot 30 images with the 24-70 and never matched the 70-200 in sharpness, not only at the focal point, but also as the image radiates outward on the trunk.  When I used f10 on the 24-70, I matched the 70-200 @ f2.8 in sharpness. But the 200 was shot at 2.8, not f10!

What's going on here? I thought for sure the 24-70 would deliver a sharper image hands down than the bigger lens just due light having to pass through more glass.
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FWIW, my 24-70 is softer at the longer end (70mm). I've seen the same with a couple of other 24-70s.

[Phuong]

you didnt say at which speed you shoot the pictures and wether they're on tripod or handhold. i'm assuming it's handhold. it could be the IS on the 70-200 though. also, like francois' , my 24-70 tends to be softer at the longer end as well.

ultimately can you show the photos? without photos it's hard to say anything

[dwdallam]

you didnt say at which speed you shoot the pictures and wether they're on tripod or handhold. i'm assuming it's handhold. it could be the IS on the 70-200 though. also, like francois' , my 24-70 tends to be softer at the longer end as well.

ultimately can you show the photos? without photos it's hard to say anything
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Tripod for both. In order for you to see the photos I'd have to up load the RAW files, which are about 6 megs each.

If the 24-70 is softer at the long end, then that probably explaines it. The 70 to 200 was at its short end. As for the shutter speed, tehy were both shot in midish daylight, so I suspect the shutter was about the same for both--probably so close as to not matter. I so remeber that the 70-200 was more overcast, so it could have been a little slower even.

Anyone else want to chime in?

[Ray]

You've got two factors here working to produce a softer image from the 24-70. First, it is true that generally telephoto lenses tend to be softest at their longest end. But it's also true that a 67mm shot will not produce as sharp a result as a 75mm shot even assuming both lenses are of equal quality.

[dwdallam]

You've got two factors here working to produce a softer image from the 24-70. First, it is true that generally telephoto lenses tend to be softest at their longest end. But it's also true that a 67mm shot will not produce as sharp a result as a 75mm shot even assuming both lenses are of equal quality.
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OK, would you mind elaborating on this? As you have left it, I'm not getting any useful information here, but it sounds important.

[Ray]

OK, would you mind elaborating on this? As you have left it, I'm not getting any useful information here, but it sounds important.
[a href=\"index.php?act=findpost&pid=69496\"][{POST_SNAPBACK}][/a]

When comparing the quality of 2 lenses, it's necessary to reduce as many variables as possible, which means you should use a tripod, remote cord, MLU if shutter is likely to be slow. You should also make sure that focussing is the same for both lenses, and in the case of zoom lenses it's particularly important that the focal length is the same.  

You haven't done that in this test. You've compared 2 lenses of different focal length shooting a tartget from the same distance. In such circumstances the shorter focal length is at an inherent disadvantage as regards sharpness. An 8mm difference in this range of focal lengths would be noticeable even if the lenses were of the same quality.

People some times forget this factor when they drool over the superior performance of prime lenses. Any sharpness advantage over a zoom is only apparent if the scene requires close to the exact focal length of the prime lens. If you have to crop the image in the final editing, because you couldn't get a little bit closer to fill the frame, or didn't have time to change lenses, then you've lost that sharpness edge which was perhaps the main reason for using the prime in the first instance (although not necessarily the only reason).

[dwdallam]

Well it wasn't a test really, just an observation. Do you have any verifiable information on sharpness and focal lengths of the two lenses?

I guess the real question here is this: At their entire range from 24-70 and from 70-200 under equal conditions (shutter speed and aperture, among other variables), which lens will be sharper and why?

Does anyone know of a test where the sharpness of the two lenses here have been compared?

[DarkPenguin]

From 24-69 the 24-70 crushes the 70-200.  From 71 up tho, the 70-200 is king.

Try photozone.  They will not directly compare them but the tests should give you an idea.

[dwdallam]

From 24-69 the 24-70 crushes the 70-200.  From 71 up tho, the 70-200 is king.

Try photozone.  They will not directly compare them but the tests should give you an idea.
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Very funny. hahaha. I'll try the site you have here also. Thanks

[dwdallam]

From 24-69 the 24-70 crushes the 70-200.  From 71 up tho, the 70-200 is king.

Try photozone.  They will not directly compare them but the tests should give you an idea.
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Photozone says that the old 28-70 L is a better lens than teh replacement 24-70. That's not what Luminous Landscape says, nor other reviews. So what's up with that? They seem like the odd man out on this one. All of the reviews I've read on the "new" 24-70L prefer its performance over the old 28-70.

[ErikKaffehr]

Photozone tests individual lenses lent by owners. Also Photozone's tesing is based on measurements, so it's not including subjective factors or factors outside the scope of the testing.

There is a significant variations between individual samples of lenses.

Best Regards

Erik

Photozone says that the old 28-70 L is a better lens than teh replacement 24-70. That's not what Luminous Landscape says, nor other reviews. So what's up with that? They seem like the odd man out on this one. All of the reviews I've read on the "new" 24-70L prefer its performance over the old 28-70.
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[ErikKaffehr]

Wide to tele zoom lenses are very hard to build to a high quality, a telephoto lens or tele zoom is much simpler. I have never seen really good MTF plots of any wide angle zoom, they all loose plenty of sharpness close to the edge.

The Canon 70-200/2.8 L is one of the finest telezoom lenses ever built. Zoom lenses are always a compromise, to replace the 24-70 you would need something like three lenses.

For most picture taking I would still say that any decent zoom lens is good enough. Loking at "actual pixels or 1:1" exposes any inherent problem in a lens without mercy.

Erik

I shot the same object, a tree trunk, at relatively the same lens length, but using different lenses.

Canon 24-70 L @ 2.8 at 67mm
Canon 70-200 L @ 2.8 at 75mm

The 70-200 produced a very noticeably sharper image. I shot 30 images with the 24-70 and never matched the 70-200 in sharpness, not only at the focal point, but also as the image radiates outward on the trunk.  When I used f10 on the 24-70, I matched the 70-200 @ f2.8 in sharpness. But the 200 was shot at 2.8, not f10!

What's going on here? I thought for sure the 24-70 would deliver a sharper image hands down than the bigger lens just due light having to pass through more glass.
[a href=\"index.php?act=findpost&pid=69135\"][{POST_SNAPBACK}][/a]

[thompsonkirk]

You can send the lens to Canon for re-calibration.  They re-set the "best focus point," which seems to equalize sharpness at longer & shorter focal lengths.  My 17-40 turned from a dog @40mm into a very sharp lens overall, as a result of this sort of 'therapy.'  

(BTW, don't use PhotoZone as a reference point for lens sharpness unless you have a 1.6 sensor.  They don't shoot their tests with a full-frame camera.)

[dwdallam]

You can send the lens to Canon for re-calibration.  They re-set the "best focus point," which seems to equalize sharpness at longer & shorter focal lengths.  My 17-40 turned from a dog @40mm into a very sharp lens overall, as a result of this sort of 'therapy.' 

(BTW, don't use PhotoZone as a reference point for lens sharpness unless you have a 1.6 sensor.  They don't shoot their tests with a full-frame camera.)
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The lens is still under warranty. Would this be covered under the warranty? Also, how can I tell if the lens needs calibration? Is tehre a test I can do and then link to the RAW file for one of you to look at? If so, let me know the paramters of the shot and I'll do it.

[SMGreenfield]

Photozone says that the old 28-70 L is a better lens than teh replacement 24-70. That's not what Luminous Landscape says, nor other reviews. So what's up with that? They seem like the odd man out on this one. All of the reviews I've read on the "new" 24-70L prefer its performance over the old 28-70.
[a href=\"index.php?act=findpost&pid=69788\"][{POST_SNAPBACK}][/a]

That was exactly my experience.  I returned a new 24-70 2.8L and kept my 28-70 2.8L.

Of course, I could've had a "bad copy".  I'm thinking of bringing every one of my "L" lenses down to Canon to be calibrated.  Bummer is, it takes two weeks...

Stephen

[dwdallam]

That was exactly my experience.  I returned a new 24-70 2.8L and kept my 28-70 2.8L.

Of course, I could've had a "bad copy".  I'm thinking of bringing every one of my "L" lenses down to Canon to be calibrated.  Bummer is, it takes two weeks...

Stephen
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If anyone has anymore information about how to test your lens for calibration, let us know. I think I'll write canon and ask them.