What are the differences between different types of focusing screens?

Question

I've seen some focusing screen questions, but I can't seem to find a general question, so I'll go ahead and ask.

Over the years, there have been different focusing screens and I'll list some below. However, what are the differences and advantages of each of them? Also, can some cameras switch out their focusing screen to a different one?

1. Split prism

2. Split image

3. Cross split image

4. Matte

And there are several others, but that'll be a good start.

I'm going to leave this for other people and future reference.

Answer 1

There are generally three main different types of focusing screens:

• Split circle with a prism collar
• Matte
• Gridded

And umpteen variants of each of these. But the first type was more common in film dSLRs and were to aid manual focus. The "split" in the middle would show you how far out of focus you were, and as you adjusted focus, the two sides of the image would align when when focus was achieved, and the prism collar would be evenly illuminated. These types of screens were mostly dropped when autofocus came into cameras, because mirrors in SLRs were no longer 100% efficient--some of the light had to be diverted to the autofocus sensors, and this was done by making the mirrors partially transparent, so that light could then be diverted to the AF sensors (typically in the "floor" of the camera body. Less light meant that the prism collar would be darker, and, well, you had autofocus now, so did you really need the split circle and collar to help you out?

Matte focus screens then became norm, and are in fact the default focus screens in most dSLRs today. The main differences you may find are "high-precision" matte screens, which simply make things a little darker and easier to judge DoF accurately.

Gridded focus screens are an aid in composition. They simply have a grid pattern on them to help the photographer align or position subjects in the composition by the grid.

Many older mid-range and pro end SLR/dSLR camera bodies have the ability to swap focus screens quickly and easily (e.g., my Canon 50D and 5DMkII do this), but these are mostly going the way of the dodo, because of a newer feature--the viewfinder LCD overlay (e.g., the Canon 5DMkIII, 7D, and 70D all have an LCD overlay and do not allow for interchangeable focus screens). Rather than having a physical focus screen that swaps out to do grid lines, an LCD panel is now in the viewfinder lightpath next to the focus screen, and can be used to turn grid lines and AF point displays on and off. Probably because of the possibility of damaging the wiring required for the LCD, most models of cameras that have an LCD overlay in the viewfinder do NOT offer the capability to interchange focus screens, although it's still physically possible to do so (i.e., the LCD overlay is usually physically separate from the focus screen, not integrated into it).

Answer 2

Most of the Canon EOS xD and xxD series (5D, 50D etc.) have user-exchangeable screens. The screens themselves are a matter of personal preference - I like the "architectural" screens with a grid pattern, handy for level horizons in landscapes and a must for working with tilt-shift lenses. Screens with splits are helpful for manual focusing, and fine-grain/precision screens are helpful for manual focusing in low light. It's all down to your dominant style of photography as to which will best suit your needs.