Extension tubes with the Canon 5D

Can anyone tell me why Canon say only one extension tube should be used? With my Pentax SF7 I could use any combination of the three extension tubes I had and for close-ups got perfect results every time.

And also, is there any reason why Canon advise that AF should not be used when a tube is fitted? With a fully electronic tube you would think that it was capable of effectively driving the AF.

All advice and ideas welcome!!

Tony Whitaker said:

Can anyone tell me why Canon say only one extension tube should be used? With my Pentax SF7 I could use any combination of the three extension tubes I had and for close-ups got perfect results every time.

And also, is there any reason why Canon advise that AF should not be used when a tube is fitted? With a fully electronic tube you would think that it was capable of effectively driving the AF.

All advice and ideas welcome!!

Click to expand...

Where does Canon say this? I've not seen the advice for my 1Ds (or D60), and have used all three
of my Kenko tubes, witth AF. My only concern would be mechanical, especially with a long lens
and a heavy camera.

Having said that, internally focussing macro lenses (I have a 100 and a 180) make life very much
easier for macro photography in the field, so I tend to use extension tubes only on long telephotos,
and usually only one. (Once you have got to 1:1 on the lens, adding extension tubes makes only
a small difference.)

In the instruction sheet that came with the extension tubes it says "Do not use two or more extension tubes simultaneously". Good to know you can use two or more on the 1D as this would suggest it is also possible on the 5D.

I'm still starting with the 5D but certainly on my Pentax I used any combination of the three tubes I had with a 28-80 macro to great effect. With the telephoto lenses I only ever used one tube but they worked equally well.

Hi, Tony:

The main reason why Canon advises users not to stack extension tubes or other coupled lens accessories like extenders is the possibility that the camera's shutter may not release. Each extra accessory increases the level of electrical resistance. But, you are welcome to try; many users have reported successful results using 2 or 3 coupled extension tubes.

Autofocus performance with extension tubes is a separate issue. Assuming no problems with shutter release, there is still the possibility that the effective maximum aperture of your coupled lens with one or more extension tubes may become smaller than f/5.6. If so, the camera's AF system may not be getting enough information to determine an accurate focus. Additionally, extreme close-up photography results in extremely shallow depth-of-field. Even if the subject matter is reasonably contrasty and the effective maximum aperture isn't an issue, the focusing motor in the lens might be driven so fast that the AF sensors can't recognize the subject. This is not to say that AF with extension tubes is impossible, but it's important to realize that the odds are stacked against it.

Manual focus is often the only practical option, even when autofocus is technically available. Under such circumstances, you may find that focusing manually while pressing the shutter button halfway allows the circular green LED in-focus indicator in the camera's viewfinder data display to function as an effective focusing aid.

Hope this helps!

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

Thanks, Chuck

Your advice is much appreciated. I'll box on and experiment with tubes and autofocus to see what is possible, but it is at least reassurring to know that in doing so I'll not be putting any of the hardware at risk.

Cheers

Tony

PS: You will probably get my same enquiry on tubes/AF via a different website route so you can ignore it!

I am so Happy to see that Canon is looking at this. Having done Macro photography as a medical photographer, I found out that the only way to get professional repeatable quality photography is with manual exposure and focus. Making Test and then preset charts, make your setting and then move the camera in and out till you get the shot in focus then shoot.