Lens quality deterioration

Do lenses lose sharpness as they age?

Several years ago, I had purchased a EF 75-300mm f/4.5-5.6 IS USM.
(That was before I joined this forum and knew better).

When the lens was new, I did some test shots at 300mm and was happy with the results -- I was able to see good feather detail on the ducks! I had also gotten some nice shots of my kids playing soccer and little league.

But now it seems that unless I am shooting at about 90mm and f/8 -- I cannot get any sharp images with this lens. I have never dropped this lens or abused it. The glass is clean. About the worst incidents that I can think of is a few times, when pulling it from the bag, the lens extended as I pulled it out.

It has gotten to the point that I don't even want to use this lens. Upgrading to one of the Ls is not currently an option.

I had this lens too. After a few years, a fungus or lubricant migrated from the edges of some of the inner elements toward the middle.

On the other hand, experience may be giving you a more critical eye.

This lens is known to be soft beyond 200mm.

In my view, it wasn't worth the cost of sending it to Canon to clean. I got the 70-200L and never looked back.

Well, maybe it is more because you now have a few lenses that are distinctly better?

The 60 macro and 17-55 IS, both regarded as excellent lenses, run rings around the 75-300, which is considered to be a mediocre lens.

Time to replace it with a 70-300 IS, or a 70-200L .

Kind regards, Wim

To your first question, the answer is generally no (except, perhaps, for lenses with elements made of ice or sugar). There are lenses a hundred years old that are as sharp as they ever were.

There are some possible mechanical issues. Lubricants can congeal or migrate (which affects poorly designed lenses more than well-designed lenses). Some really shoddy lenses with poor-quality cement may suffer separating elements or a clouding of the cement.

In an electronic lens, components such as capacitors and even insulation do age and deteriorate.

I think I have some lenses that are older than I am. Optically they are fine. I'll also bet it is mostly a change in your standards.

How are you testing the sharpness? One thought is that you originally tested with a different camera body, and now are testing with the 50D.

If you are looking at individual pixels you'd have to keep the 50D a lot more still than a lower resolution camera to make it look sharp (at the pixel level).

Thanks for the comments. I don't think it is just a change in my expectations. I had recently found an e-mail, that I sent to someone that was considering the same lens, with my test shot. I have enclosed the result. This shot was one of several taken the first day I tried the lens; the quality was pretty good.

The first is full frame on a 300D, the second is a crop at full resolution.

I don't recall if I used a tripod for this shot or not. I am going to try again with one. But basically, I have not been able to get anything nearly this crisp the last several times that I have used it.

hairy_moth wrote in post #7970050
Thanks for the comments. I don't think it is just a change in my expectations. I had recently found an e-mail, that I sent to someone that was considering the same lens, with my test shot. I have enclosed the result. This shot was one of several taken the first day I tried the lens; the quality was pretty good.

The first is full frame on a 300D, the second is a crop at full resolution.

I don't recall if I used a tripod for this shot or not. I am going to try again with one. But basically, I have not been able to get anything nearly this crisp the last several times that I have used it.

I'd suggest you try and compare this lens using both bodies, and see if there is a big difference between the two or not. The 300D is much less demanding of a lens than the 50D is, so I think you should really try and look at the same magnification rather than at 100 %.

Kind regards, Wim

wimg wrote in post #7970108
I'd suggest you try and compare this lens using both bodies, and see if there is a big difference between the two or not. The 300D is much less demanding of a lens than the 50D is, so I think you should really try and look at the same magnification rather than at 100 %.

Kind regards, Wim

That's a good point. In fact, I purchased the better lenses with the 50D for that reason (though right now, the difference seems more dramatic than I imagined).

I should do a controlled test using a tripod and both cameras.

hairy_moth wrote in post #7970259
That's a good point. In fact, I purchased the better lenses with the 50D for that reason (though right now, the difference seems more dramatic than I imagined).

I should do a controlled test using a tripod and both cameras.

Great!

Eagerly awaiting your results ...

Kind regards, Wim

If you are comparing 100% crops between a 6MP camera and a 15MP camera then you are looking at photographs of wildly different sizes.

What you are doing is like making an 8x12 print from the lens when it was new and then comparing it to a 12x18 print from the lens now and concluding that the lens has gotten worse over time.

Try making real prints from your old files and then make a print from something very similar you shoot now and compare them. Try to control for (or sort to avoid) possible issues your old shots may have had like slow shutter speeds or high ISO.

Lenses can and do lose image quality over a period of time especially with hard use.. I had both my Canon 70-200mm F/2.8 non IS and Canon 17-35mm F/2.8 sent in for a service when I worked for a newspaper..When I got them back the difference in sharpness was very noticable..

Mechanical wear and misalignment would certainly be expected with hard use.

RDKirk wrote in post #7972462
Mechanical wear and misalignment would certainly be expected with hard use.

That's what I am thinking...

The same lens on two different camera bodies of the same type (ie to XTs) can show significant differences in calibration and sharpness, much less two camera bodies of different types. Bodies are made within a range of tolerances just like lenses.