Canon EF 24-105 f/4L IS USM lens - macro performance

Today I did some measurements of the basic optical performance parameters of the Canon EF 24-105 f/4L IS USM lens in various macro configurations.

The test included:

1. The lens alone.

2. The lens with a Canon 500D closeup lens (2 diopter)

3. The lens with 12 mm and 20 mm extension tubes (Kenko).

The results are given here:

http://doug.kerr.home.att.net/pumpkin/24-105_macro.pdf

Of interest was the geometric distortion performance. With no closeup accessories, but the lens at closest focus at "24 mm", there was substantial barrel distortion (I did not quantify it). With the 500D closeup lens in place and the lens at "24 mm", there was perceptible barrel distortion. In all other situations tested (including the lens naked at "105 mm"), the geometric distortion was negligible.

Maximum magnification available with the 500D closeup lens (at "105 mm") was 0.36. In that situation, the working distance is 6.0 inches.

Maximum magnification available with the 20 mm extension tube (at "105 mm") was 0.5. In that situation, the working distance is 3.8 inches.

The lens manual gives data for the use of the two Canon extension tubes. With the EF 12 II extension tube (12.3 mm), the maximum magnification at "105 mm" is stated as 0.40. With the EF 25 II extension tube (27.3 mm), the maximum magnification at "105 mm" is stated at 0.61.

A side result of these tests is that the actual focal length of the lens at closest focus in the "105 mm" setting is about 78 mm.

I did no explicit testing for flatness of object field, but a cursory examination of the focus across the test grid suggests that it it pretty good.

It is unlikely that the Image Stabilization feature would work properly with either of these closeup aids in place, but I have no defionitive information on that.

The lens is not too far from parfocal in this regime, which allows us to use the zoom ring to "fine tune" magnification without serious disruption of focus.

[Will Thompson]

Originally Posted by Doug Kerr

It is unlikely that the Image Stabilization feature would work properly with either of these closeup aids in place, but I have no defionitive information on that.

Hi Doug,

What would factors would bring You to assume this?

Hi, WIll,

What would factors would bring You to assume this?

Well, it was based on an intial intuition that may well not be warranted.

Actully, I really just don't know.

I may do some tests on just that.

Best regards,

Doug

I did some quick testing to give me some idea as to the benefits of IS on the 24-105 f/4 IS in the macro regime.

I tested both with the lens itself at closest focus, and also with the lens at closest focus assisted by a Canon 500D 2-dipoter supplemental closeup lens.
Contrary to my intial intuition, the effect of the IS is very substantial.

Here are crops from two sample test shots, both with the lens at "105 mm" and with the 500D in place, closest focus, f/8, 1/15 sec. In each case, I took several shots in the same situation, and selected here the ones that were most representative. (For example, I had one "no IS" shot that was perfectly sharp.)

The images here are 45% x 58% crops, presented at original camera resolution. There was no postptocessing other than the cropping.
IS off:

http://images.dak.home.att.net/camer...ff_E16867C.jpg

IS on:

http://images.dak.home.att.net/camer...on_E16870C.jpg

My original thought is that, with a very close subject, translational movement of the camera (movement from side-to-side, not angular) might predominate over the angular movement of the pointing axis. (The Canon IS system provides no remediation of translational movement, so far as I know.)
Evdiently (happily) such as not typically the case.

So watch out, all you little bumblebees!

Best regards,

Doug