Lens sharpness 28-135 f3.5 vs 24-105 f4 L

I have had a Canon kit lens 28-135 for a long time. Other Canon shooters looked down their nose at it and suggested that serious photographers used the 24-105 L lens. I finally gave in and bought a used 24-105.on eBay I photographed a magazine page with a studio camera stand and an electronic shutter release. The 28-135 kit lens produced a sharp image. The 24-105 L lens produced a soft image. (see Attach)Settings were .5 sec F8 ISO 100.

What now? I'm not going to sell a lens that I know is not sharp. Can Canon fix it.? Could it be a front or back focusing problem.?

 

 

Which camera are you using? You might have a bad copy of the 24-105, but it may just need Mirco Adjustment on the phase detection AF.

 

I would do more testing using manual focus or LiveView contrast detection AF to see if you can get sharper images.

 

1/2 second shutter speed is very slow. Sometimes Image Stabilization on a tripod can make things worse.

 

You will have to do lots more testing before you can say your lens is bad.

Mike,

You are right i would not make a good scientist. I will run more tests.I used a 5D Mark 3,but I also have a 7D

Have a read of this thread [LINK] - I have given some general pointers for 'Field Testing' which should be useful to you.

 

Field testing two lenses and have an A/B comparison for 'sharpness' - a general guide:

 

Good front light

Take off all filters

Hard contrast edges on test subject (newspaper is good),

Tripod - ( A 'serious' Tripod and rock solid Head)

Camera 'square on' to Test Subject (idea: Broadsheet Newspaper stuck on vertical outside wall of building)

Fill Frame with Subject (Subject distance will change with Focal Length changes)

Image Stabilization OFF

Manual Focus at centre with Live View

Use Mirror-up Technique

Use Remote Release (or use Timer Delayed Shutter Release)

Select a range of FL for testing (idea: 24/28; 35; 50; 85; 100/105; 135)

At each testing FL make three exposures at each Full F/Stop, beginning at wide open

(i.e. for the 28~135 the shots will be at: 3.5; 4; 5.6; 8; 11; 16; 22

for the 24 to 105 the shots will be at: 4; 5.6; 8; 11; 16; 22)

 

Have a procedure so you don’t get lost; sure you’ll have the EXIF but if you have a procedure you won’t need to waste time looking at the EXIF.

 

For testing I reset the camera’s numbering so I have an easy log reference.

 

e.g. Procedure –

28 to 135 tested first, frames at 28mm; 3x f/3.5; 3xf/4; 3xf/5.6 . . .etc the first 21 frames are at FL = 28mm …

The next 21 frames are at FL 35mm

Etc

Then the same for the 24 to 105L

 

***

 

That’s reasonably comprehensive for a ‘field test’.

 

If you’re not inclined to that effort and if you do summarize, I suggest you select three FL (hard wide angle, middle of zoom, hard telephoto) for each lens and trim the number of F/Stops to being three (Wide open; middle make it the same for both lenses f/8 is a good idea; extremely stopped down, e.g. f/22).

 

I suggest that you do not skimp on making three test shots for each FL at each Aperture.

 

There is a purpose for making multiple shots of the same FL and Aperture: It is to assist to rule out, or ferret out, any anomaly that you haven’t thought of.

 

WW

William

Thank you for your detailed testing procedure.My set up,subject, lighting, camera stand, remote release is what you recommend but I obviously did not go far enough with the test. I will do it properly.

I upgraded from the 28-135 to the 24-105 several years ago, back when I was using a 20D body (8 MP). I did not do formal testing so all I can report is my anecdotal experience. I found that the 24-105 was sharper than the 28-135. On my 7D (18 MP) I am still pleased with the 24-105. As both bodies use APS-C size sensors, I can't comment on how the two lenses would compare on a full-frame body.

Its a good day when you learn something. I reran the tests according to the suggestions of Mike and William. In fact my 24-105 is sharper than mu 28-135. I was careless and I learned, if you are going to do a test, do it at least a little scientifically and don,t jump to conclusions. Thanks so much for your help.

Many of us use the 24-105mm despite its sharpness or lack thereof because it is simply so darned handy. Its problems often can be fixed in post processing anyhow.

Many of us use the 24-105mm despite its sharpness or lack thereof because it is simply so darned handy. Its problems often can be fixed in post processing anyhow.

 

Indeed. I have considered optically superior 24-70 lenses more times than I would like to admit, but I have always stuck with the 24-105 because I use the 70-105 range a great deal, and I would be constantly swapping lenses if I had a 24-70.

Edited April 6, 2019 by William Michael