300mm f/4 image quality issue

I have not been happy with the image quality from my 300 f/4 IS lens lately and thought a focus micro-adjustment would help out, so I rented a Lens Align pro from lensrentals.com and am not happy at all with what I'm seeing. Posted below is a 1:1 crop where I focused manually using the maximum magnification in live view. I don't see any place at all that has sharp focus which leads me to believe that I may have some optical issues as opposed to focus issues. The target was 25' away from my camera (50D) and I used a wireless remote to trigger the shutter, had mirror lock enabled to minimize vibrations and also had IS turned off. I also have no filter on the lens for this test.

I figured that even if I missed the manual focus at all, then I should at least see some part of the ruler in focus, but there is no part at all that is as sharp as I would expect from this lens. Anyone have any thoughts on this? Is it time to ship if off to Canon for an inspection? This is bad timing since I have a trip down to the Florida Keys planned in about 10 days and was going to use this lens for wildlife photography while there.

You know, it's funny that you brought this up. I've been having problems with mine too all of a sudden. Looks about the same. I'm using it on a 40D and a 1Dmk3.

j.

JohnJ80 wrote in post #8801378
You know, it's funny that you brought this up. I've been having problems with mine too all of a sudden. Looks about the same. I'm using it on a 40D and a 1Dmk3.

j.

Strange. Maybe I'm just too much of a pixel-peeper, but I do notice the lower image quality in "real life" situations. I shoot mainly sports action and have been favoring my 70-200 2.8 IS lately because I can rely on the great images I get from it. I really hate leaving the 300 in the bag as much as I do.

1/60 shutter speed. Was your tripod on carpet by any chance?

You need much better lighting for this test also.

Edit: Just noticed that it's a 1:1 crop also. I think your expectations are just a bit too high here....

Cesium wrote in post #8801441
1/60 shutter speed. Was your tripod on carpet by any chance?

You need much better lighting for this test also.

Edit: Just noticed that it's a 1:1 crop also. I think your expectations are just a bit too high here....

Yep, the tripod is on carpet, but I did use the mirror lock and waited a few seconds after the mirror was up before I tripped the shutter. I'll adjust the light and try some more.

You're right about my expectations, maybe they are a bit too high. I'll test my other lenses (see my sig) and do a relative comparison, maybe that'll help put things in perspective.

I agree with Cesium.

Also, if you were indeed trying to do the MA with the LensAlign, I think you were much too close to it.

How much of a crop is this?

kb9tdj wrote in post #8801488
Yep, the tripod is on carpet, but I did use the mirror lock and waited a few seconds after the mirror was up before I tripped the shutter.

Remote shutter release?
If not, use the 10sec timer. I just tried mine and even 2 seconds weren't enough to stop shake on carpet.

I missed the lighting and shutter speed. You need to be doing this with good light (like sunlight). I've seen huge variation in AF that goes away in good light with most cameras.

j.

It looks like there's maybe a tiny bit of backfocus (easily adjusted) but I don't think focus calibration is the problem (the "0" line area is sharper than the rest). The image does look soft and I agree with improving your lighting to check if that helps, but I think you may be right: I'd expect the 300 f4 to be as sharp as anything else in your bag and better than this.

One thing that may be of interest: at Lensrentals we got a large number of 300 f4 IS in Jan - Feb that were really soft and had to go back to the mother ship to be tuned up. On our Lens repair data base that lens basically went from 'never needs repair' to the top of the chart for a 6 months period ( http://www.lensrentals​.com …05.17/lens-repair-data-30 ). After that we've never had trouble again, but it makes me wonder if perhaps there was a bad batch out there.

A couple of things that jump out at me. The 300 F/4 IS is 2 stops. If you figure 1/320 is the minimum for a 300mm then 2 stops would be 1/80 and your shot was at 1/60. Also at 25' your DOF is about 4 inches so any kind of mirror shake or even manually pressing the shutter can put your focus point outside the DOF. How does it perform in real life? I love mine and the focus seem to be right on.

Michael

mspringfield wrote in post #8805749
A couple of things that jump out at me. The 300 F/4 IS is 2 stops. If you figure 1/320 is the minimum for a 300mm then 2 stops would be 1/80 and your shot was at 1/60. Also at 25' your DOF is about 4 inches so any kind of mirror shake or even manually pressing the shutter can put your focus point outside the DOF. How does it perform in real life? I love mine and the focus seem to be right on.

Michael

Seems like 1/60 should have been ok given the camera was on a tripod and and I used a wireless remote along with mirror lock to minimize vibration. Note also that the IS was turned off since the camera/lens were tripod-mounted. I have since tried the setup again outside for better lighting and higher shutter speeds and am still analyzing the results.

In real life the images do seem a bit soft. I'll see if I can dig through my collection and post a few examples when I get a chance.

kb9tdj wrote in post #8805822
Seems like 1/60 should have been ok given the camera was on a tripod and and I used a wireless remote along with mirror lock to minimize vibration. Note also that the IS was turned off since the camera/lens were tripod-mounted. I have since tried the setup again outside for better lighting and higher shutter speeds and am still analyzing the results.

In real life the images do seem a bit soft. I'll see if I can dig through my collection and post a few examples when I get a chance.

True. A tripod should have helped. I have seen a lot of people saying the the 300 F4 IS is not as sharp as the older non-IS. I may be lucky and have a good one.