Focus is soft when using the EC-D screen and EOS3

greenspun.com : LUSENET : Canon EOS FAQ forum : One Thread

I have a problem that you may be able to help me with. I have two EOS3's, one bought in late 99, the other bought in May 01. I recently bought a couple of the Tilt Shift lenses intending to use them for various reasons. Considering that my horizons sometimes look like they are slanted I decided to replace my normal matte focusing screens with version EC-D, which has 3 horizontal and 5 vertical lines etched into it instead of the normal oval shape. Unfortunately the shop I was in only had one screen and said they would order me another one (lead time a few weeks). So I get home fit the screen in the older EOS3, change the custom function (CF0=1) so that it knows its a different screen when calculating the exposure. Practice using the camera and the picture looks "soft", focus seems to be about 6 inches in front/behind the object and needs to be adjusted, ftm shapens it up but I would rather it was right first time. I tried this with several lenses (28-70, 50, 100-400) and they all give out of focus results. So I undo everything and decide to try it in the newer EOS3. After resetting the required values it works perfectly and is nice and sharp. So my question is... has anyone else come across this problem, anyone know of a solution or a workaround as the "softness" is very noticeable. Thoughts and comments appreciated.

-- Bear Summer (bearsummer@hotmail.com), June 04, 2001

Answers

Sounds like the screen wasn't seating properly. The AF sensors don't use the screen, so AF should not be affected by changing the screen. So although the image in the viewfinder may look soft, my guess is that the actual images would not be.

-- Bob Atkins (bobatkins@hotmail.com), June 04, 2001.

Yeah, I think Bob's right. I had one that didn't seat properly in an EOS 630. It looked like it was in there right, but the viewfinder looked out of focus. I just took it out & put it back in & everything worked.

-- Jim Strutz (j.strutz@gci.net), June 04, 2001.

Hi Jim and Bob, I have tried seating it several times, but I'm willing to try it again. Would be nice if the answer was as simple as "you're a clumsy oaf". I must admit that I couldn't see how it would affect the AF as (if I remember correctly) the AF sensor is behind the semi-silvered mirror and does its work through the mirror without going via the pentaprism. I guess it could just be that I've been unlucky in getting a good seating for the screen. Ok will give that (and it) a bash when I get home tonight. Thanks for your suggestions.

-- Bear Summer (bearsummer@hotmail.com), June 05, 2001.

I have had the same problem with an EOS1, without ever being able to fix it. In my experience the focus by A/F was correct, just that it didn't look focussed in the viewfinder.

Keep in mind that the image you see in the viewfinder is not the same light path that reaches the film. If your screen is out of place then the image may not focus correctly on the screen even though it is focussed correctly on the film when you take the photo. As you mention, the A/F sensosrs are not affected by your screen.

I could never correctly reseat the screen in my EOS1. I suspect, in my case, that the rests for the mirror had become worn (well used ex- pro camera) and the mirror itself was not correctly aligned. I didn't persist, and replaced it eventually with a new EOS3 which doesn't exhibit the problem.

-- Paul McSweeney (paulmcs@clear.net.nz), June 05, 2001.


Thanks for all the suggestions and help, I have tried re-seating the screen several times but it still gives a soft image in the viewfinder. I do agree that the screen doesn't effect the autofocus and I expect that any pictures I take using AF will be fine. The only reason I was intending to use the grid screen was to help with getting lines parallel when using the Tilt Shift lenses. This would be fine so long as I am willing to totally trust the Autofocus. However, and this is the kicker, Tilt Shift lenses are fully manual, there is no autofocus.... Oh well fate sure has a wicked sense of humour.

-- Bear Summer (BearSummer@hotmail.com), June 07, 2001.


Moderation questions? read the FAQ