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Focusing screen, not fine tuned
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PostPosted: Sun Oct 28, 2007 10:09 pm    Post subject: Focusing screen, not fine tuned Reply with quote
After more than one month of experience, I'm still thinking my focusing screen does need a finer tuning.
Today I've been shooting my dughter whilst she was playing the clarinet. I tried to focus the instrument, but I'm afraid I've got some back focus and what really got focused was the fabric behind.

This is the picture 100%:



Your opinions will be very welcome, as usual...
Best regards,
Jes.


PostPosted: Sun Oct 28, 2007 10:19 pm    Post subject: Reply with quote
Sorry to ear that.

But prior to any opinion based on rome real pictures, a kind of laboratory test should be done :

http://photo.net/learn/focustest/

There is also a well know problem with 350D: mis-trimed mirror :

http://www.bord-studio.com/article_01eng.php

What I may suggest is to re-fit the original focusing screen, check if the mirror is adjusted, then check with the new screen it this one needs adjustment.


PostPosted: Sun Oct 28, 2007 10:27 pm    Post subject: Reply with quote
Not noticed in the last article, but you need an imperial system 0.05" hex-key, available here for cheap for all of us in metric system countries :
http://www.dealextreme.com/details.dx/sku.5418


PostPosted: Sun Oct 28, 2007 10:29 pm    Post subject: Reply with quote
Flor27 wrote:
Sorry to ear that.

But prior to any opinion based on rome real pictures, a kind of laboratory test should be done :

http://photo.net/learn/focustest/

There is also a well know problem with 350D: mis-trimed mirror :

http://www.bord-studio.com/article_01eng.php

What I may suggest is to re-fit the original focusing screen, check if the mirror is adjusted, then check with the new screen it this one needs adjustment.

Thanks for this focus test article. I didn't mention I'm using a Virtual Village split focus screen replacement, and I got some (a lot of) troubles trying to adust it properly... Peter was so kind of driving me through the dark waters of focusing screen replacement and adjust, but I'm afraid it's still not perfect.
This shot was taken with the czj planar 50mm 1.7 (my sharpest lens) and I expected a better sharpness. On the instrument there are many artifacts, so I'm thinking the focusing screen is not well adjusted...
I don't suspect on the mirror, I didn't touch it and by putting back the Canon focus screen, everything seems ok (more difficult to focus).
I'll read the article and plan a new benchtest...
Best regards,
Jes.


PostPosted: Sun Oct 28, 2007 10:33 pm    Post subject: Reply with quote
Flor27 wrote:
Not noticed in the last article, but you need an imperial system 0.05" hex-key, available here for cheap for all of us in metric system countries :
http://www.dealextreme.com/details.dx/sku.5418


Hi Flor, thanks!. I think I got a similar one, blue plastic instead...
Best regards,
Jes.


PostPosted: Sun Oct 28, 2007 10:45 pm    Post subject: Reply with quote
BTW what about your Cosinon 28mm 2.8?. Have you had the opportunity of trying it?.
Best regards,
Jes.


PostPosted: Sun Oct 28, 2007 11:30 pm    Post subject: Reply with quote
About the Cosina, I made this shot, but no more showable actually :

http://forum.mflenses.com/viewtopic.php?p=22919#22919

I have also the Virtual Village focusing screen, but as all precision product, it may have a tiny adjustement difference between batch jobs (all the screen are re-worked on CNC machines from original SLR ones).

I have also read that , depending on the lens, AF doesn't make the focus the same way, so, on pro (d)SLR bodies, you can adjust lens by lens the film plan register distance... not difficult to understand why on a 350D you could have misfocus then !


PostPosted: Mon Oct 29, 2007 9:41 am    Post subject: Reply with quote
Happy birthday Jes

Mine is also backfocus a little and I also miss some shot.
I don't think we can have total precision by using tape or paper. Better to use what we have and wait for better days. I still don't know if katzeye is a solution.

p.s. Tell me for the clarinet shot, how many glass of champagne have you drink. You have to know that each glass is 2 more mm of backfocus Laughing


PostPosted: Mon Oct 29, 2007 3:12 pm    Post subject: Reply with quote
Flor27 wrote:
About the Cosina, I made this shot, but no more showable actually :

http://forum.mflenses.com/viewtopic.php?p=22919#22919

I have also the Virtual Village focusing screen, but as all precision product, it may have a tiny adjustement difference between batch jobs (all the screen are re-worked on CNC machines from original SLR ones).

I have also read that , depending on the lens, AF doesn't make the focus the same way, so, on pro (d)SLR bodies, you can adjust lens by lens the film plan register distance... not difficult to understand why on a 350D you could have misfocus then !


I've found that on mine (10D) the focus isn't consistent as lens focal length changes. Only a couple of mm at a time, but it's slightly annoying on macro shots. The wider the lens, the more slightly front-focused it gets.
I must do a proper series of tests with it and see exactly where the problem lies, but I've a feeling it's probably now as good as it's going to get.
I've reached a compromise position with it and it suits most of the lenses most of the time.
Part of the problem, of course, is the pixel-peeping I can do now where before slight focus errors would have passed largely unnoticed if all I was doing was printing out 6x4s or shooting at smaller apertures where the error would have been hidden. Of course, it simply might have been my previous film cameras were better made Smile


PostPosted: Mon Oct 29, 2007 4:11 pm    Post subject: Reply with quote
poilu wrote:
Happy birthday Jes....

p.s. Tell me for the clarinet shot, how many glass of champagne have you drink. You have to know that each glass is 2 more mm of backfocus Laughing


Laughing Laughing Laughing Laughing

I've got a couple of meters of backfocusing then....
Thanks!.
Best regards,
Jes.


PostPosted: Thu Jan 17, 2008 6:10 pm    Post subject: Reply with quote
I've finally given up with the VV screen and re-fitted the original standard Canon screen. Funny thing is, after all the hassle with the VV screen it's actually a relief to use the uncluttered bog-standard screen again. With all the taking out and putting back in, the little securing bracket was getting a bit fragile, so I think I'll be leaving it untouched from now on.


PostPosted: Thu Jan 17, 2008 6:33 pm    Post subject: Reply with quote
Farside wrote:
I've finally given up with the VV screen and re-fitted the original standard Canon screen. Funny thing is, after all the hassle with the VV screen it's actually a relief to use the uncluttered bog-standard screen again. With all the taking out and putting back in, the little securing bracket was getting a bit fragile, so I think I'll be leaving it untouched from now on.


That's why I have never tried it. You also could say that I am not brave enough. Wink


PostPosted: Mon Feb 25, 2008 5:11 pm    Post subject: Reply with quote
Farside wrote:
I've finally given up with the VV screen and re-fitted the original standard Canon screen.

Dave, could you update me on this. Were the problems solved when you replaced the original screen? Cheers


PostPosted: Tue Feb 26, 2008 12:47 am    Post subject: Reply with quote
peterqd wrote:
Farside wrote:
I've finally given up with the VV screen and re-fitted the original standard Canon screen.

Dave, could you update me on this. Were the problems solved when you replaced the original screen? Cheers


It's ok, but sometimes it's a little imprecise with wider angles. Overall it's better than the VV experience and I don't know that I'd be bothered trying another third party screen, especially now I've got the first of my focus-confirm adapters. Even if the VV screen had been spot-on, it was still annoyingly dark in the middle a lot of the time and just hindered more than helped.


PostPosted: Tue Feb 26, 2008 1:23 am    Post subject: Reply with quote
I've also noticed that some lenses are prone to cheat the AF sensors and do front or back focus all the times. It's clearly visible with the SMC Takumar 50/1.4. I've tested 2 samples on the 5D with the same behavior. Indeed, focus was just fine with the Ee-s focus screen.


PostPosted: Wed Feb 27, 2008 1:17 am    Post subject: Reply with quote
Flor, do you mean the screen was telling the truth and the FC was lying?
There's definitely a focus issue with some of my lenses, even if the standard screen is back in place - I must work my way through them and try to put some figures on it. At the moment the FC on the Tamrons seem to agree with the screen, I'll be interested to see what a FC M42 adapter shows, when I get one.


PostPosted: Wed Feb 27, 2008 1:30 am    Post subject: Reply with quote
The focus confirmation does not give a precise point, rather a range that is comprised between two trigger points.
It was suggested by someone that for each lens and adapter you have, you need to make tests to find out if you get better focusing by approaching the focus confirmation threshold rotating LtoR or RtoL
As for screen, you need to find out that your sight settings are correct. Cameras like EOS have this weak point, that the dioptric correction wheel can be easily misplaced by having the camera rub against your bag or pocket.
Once you are sure your sight setting is correct, if you have enough light through the lens to ensure a proper reading of the scene, the screen should never lie, unless your focusing screen was mounted in an incorrect way that is not respecting the correct distance, but this event is quite unlikely unless you messed around with the default position.


PostPosted: Tue Aug 19, 2008 7:10 am    Post subject: Reply with quote
The dioptric correction has nothing to do with the image _already_formed_ on the viewfinder ground glass. It just lets or does not let you view it sharp.

If the picture is sharp in the viewfinder, but the shot is not sharp, or the sharpness in the viewfinder is not consistent with camera AF results - it is definitely focusing screen alignment problem in the camera. Can be solved by adding/removing shims under focusing screen.


PostPosted: Tue Aug 19, 2008 12:04 pm    Post subject: Reply with quote
Are you sure you have the view finder diopter control set properly for your eye? I had that issue and finally went to my left eye because I was against the diopter control stop with my right eye. Getting the diopter adjusted properly and using my left eye was like getting a new camera..
(Nikon D50 and D200)

Maybe it isn't supposed to make a difference but it surely did for my macro shots. Every time I thought I had the eye in focus I got the back of the head. Went to the left eye, adjusted diopter and now I'm spot on..


PostPosted: Tue Aug 19, 2008 3:25 pm    Post subject: Reply with quote
Stan wrote:
The dioptric correction has nothing to do with the image _already_formed_ on the viewfinder ground glass. It just lets or does not let you view it sharp.

If the picture is sharp in the viewfinder, but the shot is not sharp, or the sharpness in the viewfinder is not consistent with camera AF results - it is definitely focusing screen alignment problem in the camera. Can be solved by adding/removing shims under focusing screen.


It was definitely a bit of both in my 10D. With the factory screen in place, things improved, but weren't quite right, then I found my method of diopter control was wrong - I was focusing it on the screen image. When I focused it on the etched screen squares it suddenly improved that extra bit - enough to make a difference.


PostPosted: Tue Aug 19, 2008 3:32 pm    Post subject: Reply with quote
My suggestion would be to use a split-circle focusing screen (aftermarket or original, if available). After I got mine and have it properly adjusted - focusing became a piece of cake. AF confirm becomes a supplementary function, as you do not need it.


PostPosted: Tue Aug 19, 2008 3:46 pm    Post subject: Reply with quote
Stan wrote:
My suggestion would be to use a split-circle focusing screen (aftermarket or original, if available). After I got mine and have it properly adjusted - focusing became a piece of cake. AF confirm becomes a supplementary function, as you do not need it.


I did.
(edit)
Perhaps I should elaborate that a bit - it reads a bit short.
I had the Virtual Village screen and at first it seemed ok, but the shimming issue became a pain in the bum - never could get it quite right and the retaining clip was showing signs of fatigue, so I took the VV screen out and re-installed the factory screen permanently.


PostPosted: Tue Aug 19, 2008 4:52 pm    Post subject: Reply with quote
Shimming can be a challenge... Sad I've done this on my 400D. Perhaps, I was lucky to be done within 3 or 4 iterations.


PostPosted: Thu Aug 28, 2008 9:45 pm    Post subject: Reply with quote
I had bought a Split-image Focusing Screen from GI with Cactus triggers. I wan't sure about these 30$ things but I can't justify if it's good or bad because I couln't understand how to use the circles and the split circle on the center.

I've made the diopty adjustment. Is there a guide about how we use this for focusing. I'm thinking of switching back to the original screen.

Mine has some issues:
- Beginning from something like f:4 the half center begins to darken. At f:16 half of the circle is black.
- While looking at my notebook's screen at f.16 the viewfinder is really ugly, I mean it loooks like there are lot's of dust on the surface or it's not a flat surface. Does this mean that it's just a crap Smile

http://www.gadgetinfinity.com/product.php?productid=16976&cat=0&page=1


PostPosted: Thu Aug 28, 2008 10:38 pm    Post subject: Reply with quote
yalcinaydin wrote:
I had bought a Split-image Focusing Screen from GI with Cactus triggers. I wan't sure about these 30$ things but I can't justify if it's good or bad because I couln't understand how to use the circles and the split circle on the center.

I've made the diopty adjustment. Is there a guide about how we use this for focusing.

What I found worked was to set the dioptre wheel so the auto-focus marks on the screen are pin-sharp. Where I'd been going wrong was trying to get the image sharp and it was misleading. If there are any markings on your replacement screen, try to get them sharp.

Quote:

Mine has some issues:
- Beginning from something like f:4 the half center begins to darken. At f:16 half of the circle is black.

That's normal for a split screen - some of them darken later than others, but in the original film cameras most of these screens were made for you wouldn't have noticed it because you would have been metering wide open most of the time.
Quote:

- While looking at my notebook's screen at f.16 the viewfinder is really ugly, I mean it loooks like there are lot's of dust on the surface or it's not a flat surface. Does this mean that it's just a crap Smile

The slightest bit of dust will show up like a rock Smile
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