18-135 Sharpness

[GenXRailmedia]

I've had this lens for a while, using it on my 650D, and I'm not loving the results.  I'm finding that at almost all focal lengths, the edges are just plain blurry.  I know that few lenses are sharp throughout the frame, and I don't expect "L" quality but what I'm seeing doesn't seem acceptable.  Yes, you get what you pay for, but even my old 28-80 USM was better than this 18-135.  (Sometimes I wish I would have kept the 28, even though it's not really wide enough for a crop body.)

The middle of the frame consistently is very sharp. I've tried stopping down (usually to no more than f/8) turning the IS on and off, and try my best to avoid camera shake. My shutter speed rarely is less than my focal length. Could my AF method have something to do with it? I usually stay on AI Servo.  I've tried manual focusing, but with the Rebel's smaller viewfinder, it's not easy and all of the times that I've tried MF, the results have been equally disappointing.  

Could I have just gotten a bad copy?  Decentering issue?  Or is something that I'm doing wrong?

[GenXRailmedia]

I forgot to mention, in case it's not apparent, that the third pic is a 100% crop of the right side.  

[Waddizzle]

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@GenXRailmedia wrote:

I forgot to mention, in case it's not apparent, that the third pic is a 100% crop of the right side.  

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I don't think you need to use AI Servo for this type of shot.  One Shot mode should have been good enough.  Your shutter speed seems to have been high enough to freeze the train.  I suppose it was not moving at a cruising speed.    

http://www.dofmaster.com/doftable.html

What would you estimate the distance between the camera and the train to be?  According to the chart at the above link, you could be seeing the far edge of your DOF.  I wish your crop were a little larger, to include some of the dome in the background.  

If you say all shots are blurry around the edges, then I will take your word for it.  But, I suspect this particular shot is close to the edge of your DOF, or your hyperfocal distance.  It's hard to tell.  I'm comparing stuff to the left to the engine, to that to the right of the engine.

Try taking shooting in One Shot mode, both with and without IS active.

[GenXRailmedia]

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@Waddizzle wrote:

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 What would you estimate the distance between the camera and the train to be?  According to the chart at the above link, you could be seeing the far edge of your DOF.  I wish your crop were a little larger, to include some of the dome in the background.  

Wadizzle, I  can post another crop if you think it may help.  I would estimate that I was about 100 feet from the train, which was traveling 23-25 MPH, for what it's worth.  

For a while, I was using AI Servo for some sports work, and it seemed to work for moving trains, especially ones that were head-on shots where the the train was coming straight at me.  Maybe it works better in different situations.  

If you say all shots are blurry around the edges, then I will take your word for it.  

Well, maybe that statement was a bit of an exaggeration on my part.  I'll admit to becoming a pixel peeper lately.  It's just kind of frustrating because I've seen the work of a few of my friends who are using this exact same lens for the same type of (RR) photography and their stuff is completely sharp throughout the frame and I wonder why quite a few of my shots aren't.  I know that cropping the soft/blurry edges is an option, but I try to avoid it doing so wherever possible.   

 Try taking shooting in One Shot mode, both with and without IS active.

I've taken 400-500 shots with this lens since I got it last summer.  I may need to just take it on a day trip and take 400-500 shots just in a single day at a variety of settings and see what works best.  Maybe it is something in my technique.

Heres another that I took last week, this time at the long end, with a 100% crop of the right side.  I noticed that for this one, I  had switched over to One-Shot AF.  Maybe it's just me, but the right side doesn't just look soft, it looks blurry.  Again, I understand that the extreme edge isn't going to be as sharp as the middle,  and it's on the edge of the DOF, but I think it could be much clearer.  All of the detail just seems to run together.  

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[Waddizzle]

GenXRailmedia,

I am surprised to hear you say that you were 100 feet from the engine in the original shot you posted.  At a 35mm focal length, it looks more like 2 car lengths or less, or somewhat less than 50 feet, possibly close to 30 feet.  A distance of 100 feet is pretty far.  A basketball court is 90 feet.  Baseball bases are 90 feet apart.  Do you think that you were farther away than that?

How sharp is the front of the train, or wherever the focus point was established?  You will get your best results on most shots by using One Shot mode, and using the center AF point.  

What is the full model number of your lens?  The STM version of the lens is pretty good, but sharpness does fall off.  I still think most of your issue is related to depth of field.  These photos are not very good for evaluation as "test shots".  There are images that you can download and printout to use as test shots.  But, I have used the lines of a large empty parking lot to test super telephoto lenses.  The lines that define parking spaces are evenly spaced, and at known distances apart.

I think your lens is operating properly.  It is human nature to reject that which we do not understand.  But, it is quite possible that you are more likely seeing the limits of your photography skills, than the limits of your gear.  Your evidence that your lens is not performing well, raises more questions than resolving them.

[GenXRailmedia]

(I'm a little late getting back to this, it's been a busy week.)

Wadizzle, it was a bit remiss of me to not mention it in the original post, but this is the 18-135 IS STM lens.  

To answer your question about how close I was:  I went back and looked at it again.  100 feet may have been too much -- I was still a good 50 feet away.  

As far as as the focusing:  I looked at the raw file on DPP; the nose of the engine is sharp, the center AF point was just to the left of the nose of the engine.  

[kvbarkley]

Here is a site that gives a testing methodology and some test charts:

http://www.bobatkins.com/photography/technical/testing_lenses.html

[Peter]

You can use Live view and the focus box. Live view is slower but hasn´t any AF variance issues. Focus at something in the edges and upload a new picture.

I also have a question for you. Where did you get your camera, because your firmware version is 5.5.9. It feels like a service firmware. Do you have a factory menu?

[GenXRailmedia]

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@Peter wrote:

You can use Live view and the focus box. Live view is slower but hasn´t any AF variance issues. Focus at something in the edges and upload a new picture.

I have never been a huge fan of live view except for video and the occasional indoor shot of the kids, , but to be fair, I've never really used it for my action photography.  I've always preferred the viewfinder, because I may only have a few seconds to get the composition where I want it when my subject is approaching at 50MPH.  

I also have a question for you. Where did you get your camera, because your firmware version is 5.5.9. It feels like a service firmware. Do you have a factory menu?

Funny you mention that.  Yes, when i purchased the camera (used) it did have factory firmware on it.  It has since been removed.  If you are interested in the back story, you can go back and see my user posts from a few months ago about the whole debacle.    

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[ebiggs1]

I don't think there is anything wrong with the lens.  It is what it is.

I may point out, you took the worst part (right edge and behind) of your shot for IQ and enlarged it to pixel level.  Also an extreme condition.

Switch your shooting mode to One Shot.  There are few, very few, reasons to use AI-Servo certainly not this one.

The only way you can confirm the IQ of a lens is with a test target and a dedicated series of tests..