canon 24-85mm vs. 85mm f/1.8 test

[tonkabui]

i just got the 24-85mm so today, i tested it against my trusty 85mm prime. usually zoom lenses get quite a bit soft at the long end, so i figured it was a good starting point to see how well the new lens stacks up against one of canon's finest.

testing parameters:
camera: canon 20D
parameters: set2 with contrast and sharpness at +1
ISO setting: 800
WB setting: AWB
compression: JPEG LARGE
self timer: mirror lockup
tripod: bogen manfrotto 3221N with 3055 medium ball head
focus method: AF

first thing i noticed was that the zoom at 85mm is actually a little bit wider than the prime.

24-85mm
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf45resized.jpg


85mm f/1.8:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf4resized.jpg

as you can see, the prime is a tad tighter.

now on to the surprises:

85mm f/1.8
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf18crop.jpg

24-85mm f/4.5:
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf45crop.jpg

as you can see in the 100% crops, the zoom and the prime both wide open are almost equally as sharp. i must say, i got really lucky with my zoom! the prime barely edges out a win here.

and more comparisons at various apertures:

85mm f/2.8:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf28crop.jpg

85mm f/4:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf4crop.jpg

24-85mm f/4.5:
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf45crop.jpg

[tonkabui]

and more testing:

85mm f/5.6:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf56crop.jpg

24-85 f/5.6:
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf56crop.jpg

85mm f/8:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf8crop.jpg

24-85mm f/8:
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf8crop.jpg

85mm f/11:
http://www.msprotege.com/members/tonkabui/85mm%20test/85mmf11crop.jpg

24-85mm f/11:
http://www.msprotege.com/members/tonkabui/85mm%20test/2485mmf11crop.jpg

so as you can see, the 85mm is sharper throughout. it was a tad soft at 1.8, but nothing to write home about and nothing a little USM in PS won't fix. what really surprised me was how well the zoom held up in this unscientific test. i was expecting a dramatic decrease in sharpness compared to the prime, but it held its own quite well. the 85 was tacky tack sharp by f/2.8, razor sharp by f/4 and stayed sharp all the way up to f/11. the zoom did quite well at f/4.5, almost matching the prime at f/1.8. by f/5.6, it got pretty darn sharp and remained that way to f/11.

[ed rader]

i've owned both lenses. the 24-85 t'ain't bad but the 85 1.8 is superb.

ed rader

[wimg]

Hi, thank you for those shots. It shows what to expect from the 85 I currently have, including at F/1.8, so mine is going back to the dealer :).

Kind regards, Wim

[TimothyHughes]

If I read this correctly you are comparing the prime (wide open) at f/1.8 to the zoom at f/4.5 (wide open)? That's really not a valid comparison.



as you can see in the 100% crops, the zoom and the prime both wide open are almost equally as sharp. i must say, i got really lucky with my zoom! the prime barely edges out a win here.

[tonkabui]

If I read this correctly you are comparing the prime (wide open) at f/1.8 to the zoom at f/4.5 (wide open)? That's really not a valid comparison.


well, this whole comparison isn't really valid because one lens starts at 1.8 and the other starts at 4.5, so if i closed the prime down to f/4, i have to close the zoom down to f/8. the whole point of this comparison was to see how well the 24-85mm performed overall compared to a lens i knew was sharp. how else would i know if the 24-85mm i got was a good copy or not? i was just surprised by how well the zoom did (at least in the center of the image).

[rklepper]

I am not cinvinced that the 85 is soft wide open. Possibly. But, I think it is hard to tell due to the narrow DOF. It is so easy to hit focus on something you were not intending to hit.

[wimg]

Hi,
well, this whole comparison isn't really valid because one lens starts at 1.8 and the other starts at 4.5, so if i closed the prime down to f/4, i have to close the zoom down to f/8. the whole point of this comparison was to see how well the 24-85mm performed overall compared to a lens i knew was sharp. how else would i know if the 24-85mm i got was a good copy or not? i was just surprised by how well the zoom did (at least in the center of the image).
What Timothy was referring to is that comparing F/1.8 to F/4.5 is not a valid comparison, even if it is maximum aperture for each lens. In order to compare them properly, you would have to close down the F/1.8 lens to F/4.5, and then see what teh difference is.

From your pictures, it is very clear that the zoom lens is outclassed by the prime at the same apertures. And that it is at least as good at F/1.8 as the zoom at F/4.5, tells you a lot about the quality of the prime, and less so of the zoom. It is no less than 2 2/3 of a stop difference!

Kind regards, Wim

[tonkabui]

I am not cinvinced that the 85 is soft wide open. Possibly. But, I think it is hard to tell due to the narrow DOF. It is so easy to hit focus on something you were not intending to hit.

i'm sure user error was part of its perceived softness. there have been countless times when the slightest adjustment in focus made the biggest difference in sharpness. i tried to minimize the shallow depth of field by having the target at about 10 meters away.

[wimg]

I am not cinvinced that the 85 is soft wide open. Possibly. But, I think it is hard to tell due to the narrow DOF. It is so easy to hit focus on something you were not intending to hit.
Well, my copy is soft, at the corners. And it vignets horribly until F/4, to the degree that it needs underexposing by 2/3 stop just trying not to overexpose the centre too badly. But I did establish that it has a centering defect, right bottom corner is still unsharp at F/11, and the other corners do not get sharp until F/5.6. I did take > 200 controlled test shots when I noticed this.

Compared to that tonkabui's 85 F/1.8 looks incredibly sharp. :)

Kind regards, Wim

[tonkabui]

Hi,

What Timothy was referring to is that comparing F/1.8 to F/4.5 is not a valid comparison, even if it is maximum aperture for each lens. In order to compare them properly, you would have to close down the F/1.8 lens to F/4.5, and then see what teh difference is.

From your pictures, it is very clear that the zoom lens is outclassed by the prime at the same apertures. And that it is at least as good at F/1.8 as the zoom at F/4.5, tells you a lot about the quality of the prime, and less so of the zoom. It is no less than 2 2/3 of a stop difference!

Kind regards, Wim


yeah, but closing down a lens by two stops to compare it to a lens that is wide open isn't necessarily "valid" either, is it? i'm not trying to be a smarty pants, just curious as to methodology of testing procedures.

[ed rader]

yeah, but closing down a lens by two stops to compare it to a lens that is wide open isn't necessarily "valid" either, is it? i'm not trying to be a smarty pants, just curious as to methodology of testing procedures.


i think the problem here is you are trying to compare an apple to an orange.

ed rader

[grimreaper]

Impressed with how well the prime looks wide open.

[tonkabui]

i think the problem here is you are trying to compare an apple to an orange.

ed rader


yes, i think you might be on to something here, ed. my square peg won't fit in the round hole too well. i guess all i can really say is i was able to confirm that my copy of the 24-85mm is quite sharp for what it is (a variable ap zoom that is notorious for variations in quality). and at $180, i think i got a great deal on a decently sharp walk-around lens.

[kitacanon]

The 24-85 was my first choice after I got the d30/50F1.8 and I got great shots with it...I got the 10D and feel it's a perfect fit...and then I found this PR photo...

http://img265.imageshack.us/img265/8910/10dfmb2.jpg

[ShotByTom]

As a rookie....I find this helpful. It helps me to see how a less expensive lens performs when I can see the same image taken by a lens that I know is great..

[kidpower]

For those who rely on PhotoZone MTF charts.

The 24-85mm at (F4.5) is "supposed" to be sharper than the 85 1.8 (1.8) wide open at 85mm.

http://www.photozone.de/8Reviews/lenses/canon_85_18/index.htm
http://www.photozone.de/8Reviews/lenses/canon_2485_3545/index.htm

It's also supposed to be sharper than a 85 1.2 wide open at 85 mm according to Photozone.

All score nicely, but it's an apples to oranges comparison.

[AngryCorgi]

For those who rely on PhotoZone MTF charts.

The 24-85mm at (F4.5) is "supposed" to be sharper than the 85 1.8 (1.8) wide open at 85mm.

http://www.photozone.de/8Reviews/lenses/canon_85_18/index.htm
http://www.photozone.de/8Reviews/lenses/canon_2485_3545/index.htm

It's also supposed to be sharper than a 85 1.2 wide open at 85 mm according to Photozone.

All score nicely, but it's an apples to oranges comparison.

Good point. In this case the unfair comparison is compunded by what also appears to be a "bad apple"! ;)

I would have expected the 24-85 to sharpen up at f/5.6 from many of the pbase samples I've seen. The sample used here seems a tad softer than most. While they should have much tighter results, there is no doubt that the 85mm prime is a better lens on pretty much any day.

[kitacanon]

Here's a 24-85 at 85mm...100% crop...iso 200, 1/400 @ F:9

http://img402.imageshack.us/img402/6264/2kidsccrga4.jpg