Is marking a focusing screen a bad ida?

I have a spare stock focusing screen for my 5d2.

I have a problem leveling it, too many shots are angled. I want rules of thirds in the viewfinder. Screens with rules-of-thirds cost between $60 an $100.

Is there is a reason why I wouldn't take a sharpies to the spare focusing screen and make my own lines? If it's a good idea, what would be the best way to mark it? Anybody done it?

You have nothing to lose.

I have never done it but I have thought about it many times. My plan was to use dial calipers, strait edge, and a X-Acto knife, (a sharpie will be to wide)

I agree that scribing would be a better line than a Sharpie, which would be too wide. The issue might be HOW does one scribe a line without wrecking the texture of the focusing screen, which is very fragile plastic.

A very thin bladed xacto would do the trick. Or a ultra fine point sharpie, though that will likely block out alooot of light where used.... so make sure the point is suuuuper fine.

One other technique I'll mention is to use your edge of frame as a guide. If you have a vertical subject without any z axis movement, you can use your vertical edge of frame to match up with the subject, then just simply pan over to compose your shot.

If you have the spare focusing screen, are comfortable with changing one out and replacing one, then it probably doesn't hurt to try. Just be careful. Also do your best to entirely clean the area of any dust particles, hairs, etc as you're going deep into the camera and it will be open and exposed for quite some time to do the swap.

best of luck

uOpt wrote in post #16263827
I have a spare stock focusing screen for my 5d2.

I have a problem leveling it, too many shots are angled. I want rules of thirds in the viewfinder. Screens with rules-of-thirds cost between $60 an $100.

Is there is a reason why I wouldn't take a sharpies to the spare focusing screen and make my own lines? If it's a good idea, what would be the best way to mark it? Anybody done it?

Personally it's a waste of time trying to modify a stock screen, the eg-D screen is the only real way to get the grid the screens Have such a soft coating chances are you will mark/scratch it, I think I paid £29 for my D screen and 30 seconds to change it (5d2 has quick change screens) save the headaches just pick one up ��

If its just an issue levelling shots try a hotshoe spirit level, a lot cheaper than a new screen?

The D isn't rules of thirds.

uOpt wrote in post #16297807
The D isn't rules of thirds.

Marking a focusing screen for the "rule of thirds" is rather silly in my opinion. The reason is that you may be shooting for a different final aspect ratio then 3:2. If you're shooting for an 8x10 print, for example, the scribed "rule of thirds" lines would be way off.

If you really want to scribe helpful lines on the focusing screen, what could be useful would be two lines that demarcate an 8x10 aspect ratio so you don't need to guess when setting up for a portait, for example, that will be printed as an 8x10.

The "rule of thirds" is only a rough guideline and is a rule that often should be broken in my opinion. Think about it, but you certainly don't need to have a viewfinder marred with lines for it.

uOpt wrote in post #16297807
The D isn't rules of thirds.

That's correct and in theory you can't have rule of thirds due to the aspect ratio as SkipD mentions, but the D screen has the grid to help align your subject before taking the shot without using a hot-shoe level or using a head with a built in level.
Also Hopelessdfilms made a good suggestion using the edge of frame technique, good to see old school techniques being suggested.

SkipD wrote in post #16297824
Marking a focusing screen for the "rule of thirds" is rather silly in my opinion. The reason is that you may be shooting for a different final aspect ratio then 3:2. If you're shooting for an 8x10 print, for example, the scribed "rule of thirds" lines would be way off.

If you really want to scribe helpful lines on the focusing screen, what could be useful would be two lines that demarcate an 8x10 aspect ratio so you don't need to guess when setting up for a portait, for example, that will be printed as an 8x10.

The "rule of thirds" is only a rough guideline and is a rule that often should be broken in my opinion. Think about it, but you certainly don't need to have a viewfinder marred with lines for it.

I've done this on focusing screens before--though those were medium format screens. And, yes, I used an X-Acto with a very light touch. It doesn't take a deep mark to be visible. In fact, the lines on the marked screens are inscriptions themselves, not painted markings.

Don't try to use a marker. Any marker is just too wide and will be too obtrusive.

I agree that scribing an alternate format is more useful than trying a rule of thirds or other compositional concept.