Auto-focus Usage <moved>

As I'm new to AF, just wondering if you guys always use it for 1:1 and greater. I found with my crystal shots that the AF on the 100mm L Macro was not as accurate as I had expected.

And I'm correct to switch the IS off for all tripod shots, right?

Manual focus for all my macro shots.

Yep, turn off IS when on a tripod or you will get blurred shots.

Worcester Lad wrote in post #15058107
Manual focus for all my macro shots.

Yep, turn off IS when on a tripod or you will get blurred shots.

Thanks, George. That's what I thought. Onward and upward

I'll move you to talk about.

Generally over 0.5X I use manual focus. Handheld the classic technique is to use the focus ring to set magnification move the whole rig back and forth to place the plane of focus. On a tripod this can be achieved using a focus slide.

Lester Wareham wrote in post #15060253
I'll move you to talk about.

Generally over 0.5X I use manual focus. Handheld the classic technique is to use the focus ring to set magnification move the whole rig back and forth to place the plane of focus. On a tripod this can be achieved using a focus slide.

Thanks, my bad.

Great info about the 0.5x. I just needed some confirmation it wasn't my lens. I know it's asking a lot to auto-focus at these magnifications.

AnnieMacD wrote in post #15060341
Thanks, my bad.

Great info about the 0.5x. I just needed some confirmation it wasn't my lens. I know it's asking a lot to auto-focus at these magnifications.

I have the 100 classic and that does AF fine in reasonable light to 1:1. However, the AF accuracy is generally not specific enough to ensure the focus is placed where you want.

If you are working on a tripod and have a camera with live view you can use that set to 10X magnification to get the MF set exactly where you want it.

The modern IS systems are ment to detect a tripod and turn themselves off (the older ones go into a oscillation on tripod and mess the shot). I would not trust the automatics however and just turn it off.

For best results use a cable release or timer release and mirror lockup or live view to eliminate vibration. Don't use too small an apature else the image will be softened by difraction; f/11 is a good compromise for crop cameras and f/16 for full frame.

I am also new to macro, having just got my 100L macro last week. I have learned to turn off AF, and use foot zoom to focus. I have only taken a few shots on a tripod, but I didn't know to turn off IS. -rick

There should be a switch on the side of the lens Rick, check the lens manual if having trouble.

You can't get 1:1, or any specific, magnification while using AF. You only get those magnifications when the focus is set so that the yellow/orange numbers are lined up in the focus window. As soon as you hit AF, focus tries to run and spins off of that magnification.

If you're trying to get that specific magnification, you have to set that manually and focus my moving either your camera or subject back and forth to achieve focus.

Thanks everyone for all the advice. I've just ordered a macro focusing rail which should help.

I have another question. I know the 100mmL Macro goes to 1:1 magnification. If I add extension tubes, how can I work out what the various magnifications are with the different combinations? I have as set of the Kenko tubes.

I don't think there's a generic formula for computing that. Ext tubes don't actually magnify anything, they just allow your lens to focus on object closer that it could otherwise. So, how much closer you can focus depends on how much focus travel is already built into your lens.

AnnieMacD wrote in post #15078072
Thanks everyone for all the advice. I've just ordered a macro focusing rail which should help.

I have another question. I know the 100mmL Macro goes to 1:1 magnification. If I add extension tubes, how can I work out what the various magnifications are with the different combinations? I have as set of the Kenko tubes.

It's east to work out for infinity focus, just Extension over focal length, you can work it out for close focus too but it's a bit more trouble. A full stack of tubes should get you up to about 2:1.