24-70 2.8 L vs. kit lens...unexpected results?

Falxon wrote:

did you take both shots with the same aperture setting?

Yes Falxon, F11 on both of these...thanks d

Thanks Lemming51, and while I expected lenses to operate best in the mid-apertures I was surprised to hear that they more or less perform about the same around those apertures (within reason I'm sure).

The 24-70 is a great lens...I've been taking some wide open shots around the house and it's pretty sweet.  But the irony from the exercise is that I'm also appreciating my 18-200 a lot more for the things it does well.

I will open them up and try again...thanks D

Lemming51 wrote:

DaveEdmunds wrote:

...

I set up a very quick test...shot the same scene once with each lens both shots at 40/43mm (I eyeballed the zoom setting for the kit lens so it's off by 3mm), 1/160, f11, iso 100, studio flash with my 60D.

All lenses are virtually the same sharpness (or unsharp due to diffraction ) at f/11. Try it again at f/5.6 or whatever the 18-200 is wide-open at ~40mm and see if there's a difference. Center sharpness may still be similar, but the 24-70 should be better at the borders.

Other image differences between these that should be noticable (maybe with another subject) include vignetting, barrel/pincushion distortion, and CA.

Otherwise, yes the 18-200 is a good (or at least good enough) lens for general use. It's certainly a much better lens at 80mm - 200mm than the 24-70/2.8L

Advice will be taken, I'll shoot some wider apertures and come back to the thread.

I do mostly flash shooting so maybe, without fully realizing it, I've been producing nice and clean images all along with my kit lens.  Not to say I'm not loving the 24-70...been shooting tests fully opened up around the house and it's really nice.

thx d

diness wrote:

Actually the 24-70 looks better to me in these tests... but why are you testing them at f11? Do you shoot at that aperture much? I wouldn't expect to see much difference here. As someone else suggested, try it at f4.5 (or whatever the 18-200 can go down to when it's at 70mm and you will see a huge difference.

Thanks cb, I would say that my test was fairly casual so there's a ton of room for error...I'm also going to open up the apertures to try and expose more of the characteristics of each lens, just out of curiosity.

Thanks, D

cberry wrote:

Dave,

were both shots taken in live-view at the same ISO? Same focal length?

Curious. Seems the full scene shot is slightly front focused. I'm not sure that the scene itself is able to produce a sharpness comparison unless we're comparing the same object in perfect focus.

E.g. if 1 lens needs an MFA of +8 to be sharp and the other -8, the charts on the wall will be equally in-focus but foreground and background objects will be progressively sharper with one or other lens.

Another thought is to shoot both lenses where they are both performing at their best.

I went and compared the sharpness charts (the Mk 1) on DXO at all the ranges and there's a minor difference of 25% (yes that's minor) between them. Slight focus difference I think can account for that.

Copies also vary but you should see a difference - just not a major earth-shattering one.

cb

Dave -- thanks for doing the test.

Were these shot JPEG or RAW?  The reason I'm asking is that it appears that there's quite a bit of noise reduction in both sets, and this could have decreased any differences in sharpness that may exist between the two lenses.

Best,

Art

ArtMar wrote:

Dave -- thanks for doing the test.

Were these shot JPEG or RAW? The reason I'm asking is that it appears that there's quite a bit of noise reduction in both sets, and this could have decreased any differences in sharpness that may exist between the two lenses.

Best,

Art

Hi Art, and thanks...I still have to do a v2 of this test at wider apertures but these were JPG...when I shot this right after purchasing the 24-70 I was expecting a more obvious difference between the two lenses that I thought would be easily visible in JPG so didn't bother shooting RAW.  Although given that they were shot with the aperture closed way down, I now see in retrospect that it might have made more sense to shoot RAW. Will do next time. thx D

DaveEdmunds wrote:

Thanks Lemming51, and while I expected lenses to operate best in the mid-apertures I was surprised to hear that they more or less perform about the same around those apertures (within reason I'm sure).

I've seen the later posts but I still thought this was worth commenting on. The misunderstanding here is that f/11 is not a 'mid' aperture, it's a small aperture. Ok if you have a consumer zoom which starts at f/5.6 and can be set to f/22 then f/11 is half way along the scale, but that's because the consumer zoom is only giving you a medium aperture when wide open! I try to avoid using anything beyond f/13 because diffraction softening becomes so pronounced - regardless of the lens. Sometimes you have no choice of course.

The other point is that if you do choose the aperture at which the 18-200 is sharpest (it's often 2/3 or 1 stop down from wide open) you are inevitably skewing the results in favour of the cheaper lens. The point about better lenses is that they excel in more challenging tests as well, where cheaper lenses generally don't.