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Wow, those are some great shots, @abigailblackstone. If you can do the tests that @nasa suggested then I think you’ll be able to narrow down where the problem lies. I wonder now if the lens doesn’t have a back- or front-focusing problem that would need micro-adjusting. If you have a friend with a camera that would allow that . . . I love @thefarmhand’s idea there.
@nasa, your comments are very logical and helpful; thanks so much for taking the time to share you experience with us!I will give that a try, I have 2 L lenses and friends that have cameras that should allow me to experiment. Do any of you have a list of the Canon bodies that allow for micro-adjustments?
@abigailblackstone the canon xxD series – except the 60d, the 7d’s, the 5d’s, and the 1d’s I’m 99% percent sure of this list, but, obviously, do confirm all your features before deciding on any purchase.
I might stress though, that if you have lens problem that is not afma-related a new body isn’t going to help you… could be disappointing.I might add to @nasa ‘s warning about a new camera body, just because a friend has a body that allows micro-adjusting doesn’t really help @alaskabirder any, as far as making the lens usable with her current camera. Micro-adjustments are saved in the camera body, not the lens. (Maybe you already realized that, I just wanted to make sure!)
BTW, that article that @nasa linked to is really interesting! That’s definitely a recommended read!
I did read through most of the article that @nasa posted, I agree that it was very interesting. One thing that I though of, my lens no longer fits snugly to my camera body, it used to, but now I can turn the lens on the camera some even when it is locked in. I did try the suggestion of switching camera/lens combos to try to pin point the problem. I need to look through the results.
I just put some of the pictures from my experiment into my google drive. Here is the link: https://drive.google.com/folderview?id=0B7m8TLTp62IafkxGcTdLNGQ2NlU3aExUMjczNDM3OGcxbnZHUDNrY1hyU2NiT2ZvWk5udVk&usp=sharing
I cannot tell too much from them. All of the pictures were taken from a tripod with IS off. The pictures named whatever 100mm were taken with my 100-400mm lens, the others were taken with the Canon 24-105mm L f/4.0 Lens. I also named the pictures with the camera I used. Let me know what you think.
my lens no longer fits snugly to my camera body, it used to, but now I can turn the lens on the camera some even when it is locked in
That’s very likely your problem right there! To quote that article…
The end result is the discovery that on high resolution cameras, with high-quality wide-angle lens (because side to side variation is much more apparent with a wide angle lens) a very small difference in alignment between the lens mount and the sensor will cause this kind of problem.
How small of a variation? One of his sources said as little as 20 microns (0.02mm or 0.0008 inches) is sufficient to cause side to side variation. You can only detect that amount of variation with laboratory grade laser equipment, I’m told. Medical-grade machine parts (used in arthroscopes, etc.) are expected to have tolerances of about 50 microns, (3) and it would seem unlikely that a camera lens mount would be made more than twice as accurately as a medical arthroscope. In other words, with a top quality wide-angle lens on a high resolution sensor, we can perceive a 20 micron difference, but the manufacturer probably can’t make the part more accurately than +/- 50 microns at a reasonable cost.
Of course, this is talking about wide-angle lenses, but the same principles apply. If it turns far enough in the mount, maybe the electrical contacts aren’t even lining up properly, thereby causing the AF to malfunction!
Is it loose on another camera body, or is it just on your own? I know the T3 is very cheap and plasticky, so the weight of that large lens may have “broken” the mount.
I checked when it was mounted on the 70D and it fit very snugly, it did not move at all. I don’t know if you had a chance to look at the pictures I put up, but the difference in image quality is very slight between the different combinations. If the lens mount is my problem, what would you recommend changing or replacing? Should I buy a new camera body or send mine in for repairs?
Yes, I did take a look at the pictures you sent, and it’s kind of hard to really “read” anything into them. They both look about equally sharp to me. On the other hand, the 70D has almost double the megapixels, so that makes it a lot harder for a direct comparison. Were the pictures taken using AF?
As far as broken mounts are concerned, unless your T3 is still covered under warranty, I wouldn’t bother sending it in for repairs. It’s a 4 year old entry level camera, and it would probably cost more than it’s worth to have it repaired. If you’re interested in upgrading, save your money and put it towards the new camera.
If you mount a different lens on your T3, does it have the same problems with looseness? If it is indeed a camera mount issue, then I would imagine that it would affect the way all of your lenses fit on the camera.
BTW, if you’re looking at buying another DSLR, Canon is having a Memorial Day sale…
The samples are very interesting.
Before drawing any conclusions, let me ask, what exactly were you focusing on, the top bud of the two in the middle, the lower bud, or the stone background? Were you using Automatic or Manual focus?
But here are some observations. Assuming you were trying to focus on the top bud:
70D 100mm is by far the most sharp and clear of them all.
70D 105mm is sharp, but not as clear, probably because of the glass.
Rebel T3 100mm is definitely out of focus. It appears to be focused on the background rock. The bud higher up on the stem is more in focus than the two in the center of the frame.
Rebel T3 100mm is not too bad. I would say it was in focus for the glass.Could you run tests on a subject that would allow us to precisely see the plane of focus? Like http://www.the-digital-picture.com/Photography-Tips/af-microadjustment-tips.aspx or http://contrastly.com/autofocus-microadjustment/
Ah, I see. It may be good to do the tests on a smaller subject, preferably a marked, flat surface angled away from the camera, for precision.
I guess this new information voids my previous observations. Here’s a revised version:
70D 100mm the only portion of the rock that is in focus is the bottom right section. (I assume this is not where you were intending it to focus.)
70D 105mm softer focus, and again, it appears that only the bottom right portion of the rock is in focus.
Rebel T3 100mm appears to be in focus, in the center of the rock.
Rebel T3 105mm softer focus, but appears to be in correct focus, in the center of the rock.
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