Depth-of-field preview button

[neuroanatomist]

Also when you talk about
turning your lens around and using the appropriate adapter to make a
makeshift macro lens have you done this before? What are some
of the lenses one could use to get the best results from the process
that you describe? Do the images look good?

I have not done it with a Canon dSLR, although I did many years ago with a Pentax SLR (in the completely manual lens days, so aperture was set by a ring on the lens - remember that?). The basic adapters are simple, such as this one from Adorama, which couples a reversed lens directly to the camera body. There is also anupscale version from Novoflexfor connecting areversedlens, which has a cable and second ring to transfer the control functions. In either case, these are best used with fast wide-angle lenses, and can provide substantial magnification (a reversed 28mm lens gives about 3:1 magnification). Compared to a dedicated macro lens, this comes at the cost of convenience (both in getting a proper exposure and in a very, very short minimum working distance).


An alternate manual approach is to use a stacking ring or step up/down ring adapter (as you'd use with lens filters) to reverse a second lens mounted onto a lens mounted 'normally' to the body. That's often done with a 50mm lens reversed, mounted on a standard zoom (the 50mm lens is acting as a close-up lens, similar to theCanon 500D Close up Lens). This ends up being optically similar to an actual macro lens, but suffers from significant vignetting.


All things considered, although this approach is technically possible, it's really quite inconvenient unless you're using the Novoflex, and if you are going to pay $400 for that, you might as well just get a dedicated macro lens. If you'd rather try out macro photography without springing for a dedicated macro lens, consider adding extension tubes to short focal length lenses (very short minimum working distances) or close up (diopter) lenses to longer focal length lenses. You won't get true 1:1 macro with those accessories, but you'll get a taste - and if you do later get a dedicated macro lens, the tubes (and the close-up lenses, if you are lucky/careful in your lens filter size selection) can be used on the macro lens for >1:1 magnification.

[apersson850]

On the 7D, the DOF button is included in the set of ten buttons that are programmable through C.Fn IV-1. Hence, it can have more uses than just DOF and flash preview.


Don't forget that you can use DOF with live view active. If you don't use exposure simulation, live view will increase the brightness of the rear LCD while stopping down. This makes the depth of field easier to see.