I like to use 3rd party manual focusing lenses on the 5D, their performance are sometimes way better than the Canon equivalents. I decided that i had to try the EE-S screen for the 5D since it was pretty tough to focus on the default screen. I got the screen a few days ago and it’s great, focus snaps in and out easily and I don’t have to guess where’s the exact point.
I did some critical testing yesterday and it turns out that even though the image looked sharp on screen, the actual image was not sharp. In fact, it turns out that the image need a 1degree focusing turn (towards infinity) to ensure critical sharp focus. AF focusing is NOT affected.
I was surprised and googled for some answers. I found this on www.fredmiranda.com:
“The 5D has manufacturing tolerance problems with the mirror box and the focusing screen tray. People have had problems with manual focusing, because the focusing screen may not sit in the exactly correct position. You may need to place shims under the focusing screen to correctly position the focusing screen in the image path.”
That makes sense. I tried adding shims (scotch tape) on the EE-S screen and it made the problem worse. This would mean that I would have to shave the screen to ensure correct focus. I am not going to do that, too much trouble, I’ll just compensate.
Now I know another reason why the EOS 1D series are more expensive – manufacturing tolerance. Well, I get what I pay for. Drats.
Wes
Update: Upon advice received on the forum, I took out the copper shim in between the focusing screen and the focus points. It was really dicey, didn’t want to scratch the focus points, now I know how a surgeon feels like :p. The shim came out, I tested it, put on 2 thin layers of Scotch 3M matt tape on the edge of the EE-S and the focus is 100% PERFECT finally. woohoo. Come to think of it, I spent 12-15 hours of DIYing vs spending 5k to 10k to upgrade to a 1D series for perfect manual focusing, I guess time IS money.
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