How important is auto focus and aperture control in a macro setup?

Question

I'm thinking of starting some amateur macro photography, and I'm not sure I want to go with macro lenses, due to their price.

I currently have the following lenses:

• Canon EF 50mm f/1.8 II
• Canon EF 24-85mm f/3.5-4.5 USM

And I was thinking of buying either:

• Macro Extension Tube
• Reverse Adapter

My questions are:

1. What is the difference between the tube and the reverse-ring if I want to use one of my lenses for macro?
2. How important is auto-focus in macro-photography?
3. How important is the ability to change the aperture macro-photography?

Answer 1

The answer to your first question is answered here. Both are good low-cost ways to get started in macro photography.

Autofocus is not very effective as you near 1:1 magnification. Most AF systems will struggle to find focus, you have such a narrow DOF anyway that holding focus is very hard. With anything that is not moving, you are far better to set up a tripod and use live view to focus, if you have it. Or manually focus, then move the camera to and fro to get the subject in focus.

If you have a macro lens, you may not use it at 1:1 as often as you think, in which case AF can be very handy. I use it when shooting bees - it's very hit and miss, but for me slightly more successful than manual focus.

If you use extension tubes or reversal ring, you will be forced to be a certain range of distance from your subject (you can no longer focus over a wide range of distances), so AF is not really useful at all.

Aperture is important. You have a very narrow DOF, so you will often want to stop down in order to get as much DOF as possible. Or if you are shooting hand-held you may need a wide open aperture to avoid blur. If you reverse a lens, or have manual extension tubes and aren't able to control aperture, it's not a killer blow, but it isn't ideal.

Answer 2

Extension tube (ET) versus reverse adaptor (RA):

A RA is cheaper, but you will probably have a "fixed focus" and therefore, fixed reproduction ratio -- at least on your 50mm. On some zoom lenses, the zoom ring can change the focus distance when reversed, but image quality may be poor. Reversed lenses often exhibit a notable lack of flatness of field. This may be important if you are shooting (for example) postage stamps, but a spherical focus field may actually be useful if shooting the insides of a flower, for example.

ETs are more expensive, but more versatile. You may even be able to get very expensive ones that will allow auto-focusing to work. But really, buy the cheap ones and plan to do manual focusing. Advantages: manual focus ring still works, and with your 50mm lens (at least) you can have a continuous range of reproduction ratios with three extension tubes.

Another consideration might be a bellows -- like having a continuously-variable-length extension tube. You can sometimes find these used for not much more than the cost of a set of tubes. Disadvantages: the generally don't communicate automatic aperture info, and at their thinnest setting, are still longer (smaller reproduction ratio) than the thinnest extension tube.

If you're a technical sort of person and especially if you want to do flat-field macro, go for the tubes or bellows. If you're an artsy person and saving money is really important, start off with the reverse adaptor, knowing its limitations.