Do Canon (and Maybe Others Too) Zoom Lenses Go Soft?

In general, primes produce better IQ than zooms. Having said that, I used a Nikon zoom (17-55) for a while and it yielded very nice results. It was expensive though, and heavy. I also use a zoom on my Fuji which delivers a nice IQ. But my (relatively cheap) Nikkor 35/f2 prime beats both in terms of rendering, sharpness and contrast.

Not all zooms are created equal. What may help is finding out the sweet spot of your zooms (the focal range that offers the best optical performace) and try to stick to that as much as possible. Also google for 'lens creep' maybe this is what you are experiencing?

I'd guess it might be creeping.

Hey Adam, did you switch bodies by any chance? I've read that more megapixels is prone to expose certain weak points of a lens. What looked good on 16MP might not look so good anymore on 36.

Adam, do you see this happening with different apertures on the zooms? Or is it just at a particular aperture? Also are you using auto focus or manual focus?

Cheers!

It would help to know how you use your lenses. Make a few tests at the wide end, long end, and in the middle, using F8 aperture.
The other factor is the aperture used. Quite often the apertures between F6.3 and F11 (depending on the lens) will yield much better image quality than the other apertures. If you are shooting at F16 or higher, you will experience softer images because of the diffraction.

Is the image soft just at the outside edges or also in the center? If one side is softer than the others, Canon service can realign it.

I'd have to go back and look at specific settings for various photos. I'm often in the f14 - f22 range. Sometimes shooting with live view and manual focus and other times auto focus.

The thing that really made me notice was after stitching a big panorama shot with the 70-200 II at f18 at 70mm on manual focus and seeing a stunningly sharp result when viewing at full size and thinking that lately shots with the 24-105 recently haven't been anywhere near that sharp.

The zoom is softer all over but tends to be pretty sharp in the middle and fade a bit around the edges though sometimes the edges may be 10 feet from the camera while the center is hundreds.

Haven't switched bodies all, the landscape stuff which is what the 24-105 is used for is on the 5D Mark II and always has been.

all lenses do have to be recalibrated over time. if you have an up to date camera you can do a micro adjustment to fix back or front focus. also make sure the rear lens is nice and clean i had issues with that once.

---Mike Savad

I don't like my "L" 24-105 IS zoom that was the kit lens with my Canon 6D. Too soft for my tastes. Even on a tripod. What's the point of a zoom if you shoot at the far end and its soft? If the lower end is the only usable part then you are better off with shorter focal length.

I swear by primes. I have the Canon 35mm f/2 IS and the Canon 85mm f/1.8 which are both excellent and reasonably priced. I also have the Canon 50mm macro which hunts on auto focus but is outstanding for manual focus still life and food photos.

These primes are shorter and lighter. They balance the camera weight nicely and don't pump dust on to the sensor.

Suggestion - take a look at bunch of your images and see what the most common focal length used was - the result might just be your next prime purchase.

I have heard from more than a few that the 24-105 gets soft especially at the far end. ALL of my lenses have their sweet spots and sweet areas. The 100mm macro was tack sharp wide open but became soft above f16 and was unuseable at f32. My 50mm macro on the flip side is tack sharp at the higher f numbers up to and including f32.

Long exposures may lead to lens creep if you have it pointing up or down at all and this is especially true with the larger glass.

To be technical btw, the 24-105 is not a prime. Primes are fixed focal lengths.

I've been noticing the same thing, Adam. My main lens is a 100-400 but I usually only go up to 350 because it's always been a little soft at 400. I'll have to send it in soon anyway because I can't even tighten it up at all anymore...it just hangs out at 400, fully extended. I've heard that's a problem with this particular lens.

One reason for my lens problems might be due to the dunk I took in a river awhile back though! I was pinned under my bike for a few seconds before I could get my camera out of the water.

Adam,

I try and find a few images that you're not happy with and "reconstruct the crime scene". Were you using a tripod? Was it windy,was it a very long exposure or a short exposure that could have been affected by the mirror slapping up? Are the f-stops on the images all around the same f-stop on the lens(f22) or something. When you panned the tripod head, did the center of gravity change? Were you using MLU and a release cable?

Here's a pretty good tutorial on "micro-adjusting" your Canon lenses(which I haven't done yet!):

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

Rich

Hey Dean, I am not Adam, but "did you switch bodies by any chance?"
I do switch bodies between film and digital, if that will help. I do not really see the difference, except my film gives me better natural resolution. My Digital is an older one, and a bit on the slow, my film is even older, and can out shoot the Digital in speed and quality. But as far as the lenses go, all but the 500mm work equally on both bodies. And I shoot Nikon also.

Another one for micro-adjustments:

http://www.ophrysphotography.co.uk/pages/tutoriallensmicroadjustment.htm

I don't know if this is helpful or not but I read somewhere that all zoom lenses are softer at the zoomed in end. For example I have a 70 -200 lens but I always shoot just shy of that when using the zoom at around 180 or so and the image is a little sharper than it would be at 200 (I've tested this and it is sharper pulled back a little). This may be different than what you are referring to though. It sounds like you are saying throught all the focal lengths it is off in which case its something in your lens that as the others say above you should get recalibrated.

Also, make sure you have the latest firmware for your camera in case they have updated it.