SOLVED!!! Focus Screen installed- problems with fast lenses.

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

Hello,

I recently installed a focusscreen in my Eos 1000D.
The first tests indicated that I had a big front focus problem and needed to remove the original canon shim.
So I did and then I had a back focus problem so I adjusted with shims I made out of very thin plastic.
Checked again and it seemed to be well adjusted.
So far so good but I still have shots out of focus with fast lenses. Especially my Tak 50/1.4
I use also focus confirmation in combination with the focus screen and the screen indicates correct focus, the focus confirmation confirms this and when I take the shot the focus is not spot on.
When I use the lens @ F2 or higher things improve.
Could this be micro-movement? Or is the focusscreen nok?

vulko · Posted: Thu Aug 12, 2010 9:01 am Post subject:

I'd say its the screen problem you have. You shouldn't get front or back focus with manual focus lens.

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

actually you can have front and back focus.
if the focusscreen is a little closer or further from the prism, you can see the image as sharp, but the image recorded is not in focus.

visualopsins · Expire: 2025-04-11

The focus screen is too 'slow' to show dof changes below f/2; the fresnel lines are not fine enough to bend light rays from the outer perimeter of the lens front element through to eye; the perimeter light rays do get to sensor so out-of-focus is recorded.

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

And are there any screens out there that can do this? katz eye?

Regards,

kuuan · Expire: 2014-12-26

hm, though I do not have any of the technical knowledge of visualopsins, I'd say that yes I can focus my 1.4/50 Tak at @f1.4 correctly, both with a cheap chinese split focus screen in one, and a Katz Eye in the other camera.

I had needed a long time to calibrate the focus screens correctly though.

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

I checked again and see clearly that when object is in focus, i can still turn the focus ring without any apparent change in the viewfinder. When i take pictures at the different stages of being in focus, i can see the dof change. Above f2 this problem is gone. I think i will have to look out for a katz eye.

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

I have rechecked everything and decided to start all over again.
After putting the original screen and shim back everything was ok.
I removed the standard screen and put in the split screen and left the original shim.
Results were very good.
Seems i had removed the shim the first time and put it back the wrong way. this was causing the frontfocus the first time. (stupid I know)

While i was having good results I tried to test my homemade focus screen for my EOS D30. I removed the orginal shim and put my homemade screen in. The focus was spot on with my Tak50/1.4.
Next project will be an F3 or K3 screen from nikon for my 1000D.

Thanks for the input eveybody.

Regards,

Jurgen

torbod · Joined: 31 Jan 2010 Posts: 379 Location: Sweden

Glad you fixed it finally.

Just a question, how do you make DIY focusing screens?

BR
T

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

Just find a broken slr or buy a nikon f3 or k3 focus screen and then measure your original screen and cut /sand the second screen to the required size. You might have a small problem when the screens thickness is different, but that can be solved by shims or sanding the sides of the screen to make it flatter. I used an old slr screen, cut it to size installed it without a shim and it works perfect. Will post pictures soon.

LucisPictor · Expire: 2013-12-03

vulko · Posted: Thu Aug 12, 2010 9:28 pm Post subject:

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

Yes, i found out the hard way.
But nog i am able to focus within a margin of about 1 mm when I do a ruler test @ 45�. So it accurate enough now for me.
I find it even more accurate then my focus confirmation adapters.

And much more visual. You can see the prisms disappear when focus is achieved. so you also see the DOF change when you focus. very good indeed.

Next camera I will need to spend some more money and buy a FF. Smile

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

Yes I know, but once you know the impact, you can adjust accordingly.

But for now I used an old russian focus screen. Metering is perfect with this screen. No split image just a BIG circle of micropisms. No Black out of the prisms even at F11. And the viewfinder of the D30 is bigger then the 1000D. So it is very easy to achieve correct focus on my D30 now.

Where do you buy the F3 or K3 screens from?
Is the thickness of the nikon screens a problem?

vulko · Posted: Fri Aug 13, 2010 7:48 am Post subject:

my_photography · Expire: 2016-12-25

zippie · Joined: 11 May 2009 Posts: 80 Location: Belgium

Hello,

As promised some pictures of my homemade focus screen.
The screen comes from a Zenit TTL.
This is normally a focus screen in 2 parts.
1 part with the micropisms and the second screen is a milky white screen with a clear circle in the middle.
I only used the microprism part because the image is so much brighter.
Metering is not affected as far as I could test.

I tried to take some picture trough the viewfinder ofthe D30 with a P&S camera. so the picture quality is not great.
Image out of focus.

Image in focus. (focus on top of the chair)
If you look closely you can the parts out of focus trough the chair.

And finally the focus screen installled in the D30

And offcourse the picture taken with the D30