topic Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem in EF & RF Lenses

Canon ef 100mm f/2.8L macro IS lens - close focus problem

Photo-Nature — Mon, 19 Aug 2024 16:30:55 GMT

Hi,

I have a Canon ef 100mm f/2.8L macro IS lens.

The "autofocus" mode does not allow to focus as close as in manual mode.

Is this normal ?

Al,

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

p4pictures — Mon, 19 Aug 2024 17:06:27 GMT

It might be normal depending on where the lens focus limit switch is.

I have the EF 100mm f/2.8L Macro IS USM myself. If the limit switch is in the central position 0.5m to infinity then autofocus will only work between 0.5m and infinity, yet in manual focus the whole range from infinity to 0.3m is usable.

The focus limit switch is not a hard limit on the lens, but a limit for the AF system.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

normadel — Mon, 19 Aug 2024 19:15:10 GMT

Do you have the manual/user guide for the lens? Here it is.

https://gdlp01.c-wss.com/gds/2/0300003522/02/ef100f28l-macroisusm-im2-eng.pdf

It discusses minimum focus distance for closeup shooting.

Are you too close for AF to work?

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

Photo-Nature — Mon, 19 Aug 2024 23:51:34 GMT

Whether I select "Full" or 0.3m to 0.5m I have always been able to focus a little closer when the autofocus is off.

As Brian mentioned, this may be normal.

Thanks to both of you

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

p4pictures — Tue, 20 Aug 2024 07:48:53 GMT

It's not possible to focus closer than 0.3m with this lens even with manual focus. The subject distance is measured from the sensor plane, not the front of the lens. On each EOS camera there is a small circle with a line through it on the body that is the indicator of the focal plane. On some cameras the icon is painted white others it is just a mark in the body, it is usually next to the hotshoe.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

Photo-Nature — Tue, 20 Aug 2024 15:54:07 GMT

I can actually focus closer manually than with autofocus.

This situation may be caused by the adapter I have to use with my mirrorless camera.

Al,

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

normadel — Tue, 20 Aug 2024 18:48:46 GMT

The manual indicates minimum distance from the sensor plane AND from the front of the lens surface.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

shadowsports — Tue, 20 Aug 2024 20:27:46 GMT

Greetings,

I have the RF version so I haven't seen how an adapted lens behaves. If you aren't using a Canon adapter, results and consistency may vary.

With both RF and EF versions of the lens, there are some conditions where manual focus works more reliably depending on settings and shooting conditions.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

Photo-Nature — Wed, 21 Aug 2024 17:31:14 GMT

Hello,

I think I found out why the autofocus doesn't seem to be able to focus as close as in manual mode.

I did a real test bench with a tripod, a focus rail, a lens test sheet and in perfect light conditions. I tested with a mirrorless camera and with a mirrored camera.

The results show that the minimum focusing distance of 0.3m is reached whether in "autofocus" mode or in "manual" mode, and this with both types of camera.

That said, with the type of photography that I practice it is difficult in the field to reproduce these perfect conditions.

I mainly use this lens at night for moth photography and small insects. I attract insects with Compact Fluorescent Lamps (CFL) positioned in front of a backdrop.

When I shoot very small insects, I am very close to my subject and often my body, the camera and the lens partially block the light. The autofocus then has difficulty capturing the texture of the subject. This is obviously not the case when I switch to "manual" mode.

There is also another factor that contributes to the problem. In the case of very small insects, the size of the collimator can be twice as large as the insect. If the background is even slightly textured, the autofocus is on the background.

So this is why it often happens to me that the autofocus is not able to focus as close as in "Manual" mode. It is simply a lack of light and the very small size of some subjects.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

normadel — Thu, 22 Aug 2024 04:18:06 GMT

With extreme closeups and the extreme magnification, the depth of field is extremely thin, so focusing moving insects would be nearly impossible.

Re: Canon ef 100mm f/2.8L macro IS lens - close focus problem

shadowsports — Thu, 22 Aug 2024 05:02:35 GMT

Agree. This is stated in the manial as mentioned previously.