My first L glass (front focus/short focal length).

Canon EF 24-105mm f/4.0L IS

11/11/2009 11:59:16 AM · #1

I just bought an EF 24-105 f/4 L IS.

I was very glad to open the box and mount the lens on my camera (450d), but when I started to shoot I felt the imagens were a little soft and blurry.

I made some tests and noticed that the lens is front focusing... I will do some more tests with two other camera bodies from my friends (500D and 7D) to check the compatibility (and also the capability of micro focus adjustments on the 7D).

The reason for this post is: I compared the 24-105 (at 105) with my 100mm 2.8 macro (shooting the same still object from a tripod).

The macro lens (besides this shorter focal length) is magnifying the objects more than the 24-105 at 105 (the tripod and the subject were at the same place).

Is this normal? Am I missing something here?

edit for clarification

Message edited by author 2009-11-11 12:05:11.

kirbic

Canon EOS R5

Canon RF 24-70 f2.8 L IS

11/11/2009 01:27:31 PM · #2

It's possible that at closer focusing distances, the macro lens changes focal length. This is not uncommon at all. Make sure when you do this test that your subject is at least a few feet away. I haven't heard anything about the 42-105 not actually reaching 105mm, but that doesn't mean it isn't also a possibility.

franktheyank

Canon EOS-5D Mark IV

11/11/2009 02:44:46 PM · #3

Make sure you have your Image Stabilization turned off when mounted on the tripod.

Photologist

Apple iPhone 14 Pro Max

Canon EF 70-200mm f/2.8L IS USM

11/11/2009 03:56:03 PM · #4

There are a few ways to test your front-focus/back-focus issue.

- Focus Testing article

- Use the focus charts at the end of this document to test your front-focus/back-focus issue.

- Another article on focus testing.

Canon EF 24-105mm f/4.0L IS

11/11/2009 08:17:44 PM · #5

Hey guys,

Thanks for the help!

I did turn off the IS when on the tripod... and made one shot at manual focus (with live view magnification) versus another shot with autofocus...

I will read the articles posted here, and also try to make some shots from a litte bit far (because of the strange focal length issues with my 100mm vs 105mm, as I told on the OP).

After the weekend tests I will try to post some results here.

Thanks again!

franktheyank

Canon EOS-5D Mark IV

11/11/2009 08:38:48 PM · #6

Jose,
When you use Live View and Manual focus it really helps to zoom in on the viewfinder.

Canon EF-S 18-135mm f/3.5-5.6 IS USM

11/12/2009 06:45:32 AM · #7

Originally posted by franktheyank:

Jose,
When you use Live View and Manual focus it really helps to zoom in on the viewfinder.

I did it! 10x zoom!

Anyway, thanks for the tip Frank!

jent

Canon EOS-90D

11/13/2009 01:54:33 AM · #8

Originally posted by franktheyank:

Make sure you have your Image Stabilization turned off when mounted on the tripod.

Sorry for my ignorance, but what is the reasoning for this?

franktheyank

Canon EOS-5D Mark IV

Canon EF 24-105mm f/4.0L IS

11/13/2009 02:10:57 AM · #9

Originally posted by jent:

Originally posted by franktheyank:
Make sure you have your Image Stabilization turned off when mounted on the tripod.

Sorry for my ignorance, but what is the reasoning for this?

I'll quote Scott Kelby in "The Digital Photography Book Volume 1" ..."The non-technical explanation why is, these VR(Nikon)or IS(Canon) lenses look for vibration. If they don't find any, they'll go looking for it, and that looking for vibration when there is absolutely none can cause (you guessed it) some small vibration.

jent

Canon EOS-90D

Canon EF-S 18-135mm f/3.5-5.6 IS USM

11/13/2009 10:51:29 AM · #10

Interesting, makes sense. Thanks for the explanation, it might explain a few bad photos I have had on my tripod.

Canon EF 24-70mm f/2.8L USM

11/13/2009 08:38:27 PM · #11

So...

I did some test shots... real life ones and with some test charts... always with the feeling of front focus...

Today I went to a friend´s house and tried with his camera (T1i). Same results...

The lense is definitely showing front focus...

The shot below is a crop of a picture of my tie. I oversharpened it and used find edges to show off the DOF. The black dot is where i focused.

For me, the focus point is on the edge of the DOF. I dont think that this is acceptable (mainly on a $$ 1100 glass)

What do you think? Should I return the lens to the dealer? Do you think that they would give me another glass?

violinist123

Canon EOS-6D

11/13/2009 10:29:34 PM · #12

What's with the black dot, did you draw that on? Use the canon software, it will show exactly where the focus was.