Focusing with Haoda split screen

[STFM]

There's a lot of talk on the Canon forums about focus issues. I myself have found the 350D to be quite poor at focusing with most lenses at times. Especially in low light. I decided to try out Haoda's split screen.
http://groups.yahoo.com/group/screen4dslr/

First I got a screen that quite simply didn't fit. Haoda was very friendly about it, but seemed genuinely surprised by the fact a screen was bad. After double checking my installation via email, I got another in the mail.

It makes a big difference to be able to verify focus. My sigma 30/1.4 was off at times, and without split focus it was impossible to tell. Also, I use a couple of old Nikkor lenses that were really hard to focus manually before. Now it's spot-on every time. I find manual focus to be about as fast as auto focus, and much more reliable.

I highly recommend that everyone with focus issues try this out, as it's really cheap and quite easy to install/uninstall.

 

[Shane Pope]

Hi there can you give us some indication of cost and the time invioved in the installation.

Thanks in advance

Shane

 

[Arjen van Andel]

Why don't you need the shim for this screen? Is is made to the specs of YOUR camerabody?

The original shim is there for a good reason, it cancels out any production and assembly tolerances. By removing it you loose the calibrated state of the body!

Arjen.

 

[kenw]

I don't have the screen, but this has been discussed a few times in the past in threads I've read. Haoda has found that the vast majority of cameras all have the identical shim installed so he can make the screens the proper thickness without the shim. If a customer discovers they are the rare case in which they have a different shim he ships them a different screen.

At least as of a few months ago I think he had determined that the population of 350D/XTs out there actually had two shim values and for that camera he shipped screens designed to use the shim. For the 20D/10D/300D he ships screens that don't use the shim.

I don't want to put words in his mouth, you might post a question to his yahoo group and ask specifically there.
--
Ken W
Rebel XT, DSC-S85, and a whole lot of 35mm and 4x5 sitting in the closet...

 

[STFM]

Mine was installed with the shim, and was supposed to be.

Why don't you need the shim for this screen? Is is made to the
specs of YOUR camerabody?

The original shim is there for a good reason, it cancels out any
production and assembly tolerances. By removing it you loose the
calibrated state of the body!

Arjen.

 

[Arjen van Andel]

Mine was installed with the shim, and was supposed to be.

From mr. Haoda's website:

3. You do not need the copper shim for my screen. Keep the shim and original in a safe place. You can change it back as long as you wish.

I think it would have been much cleverer of Haoda to design his screens with the existing shim in place. That way you always can use his screen, no matter how far of the body is.

Arjen.

 

[Arjen van Andel]

Haoda has found that the vast majority of cameras all have the identical shim installed

Hmm, that doesn't sound good to me. There are so many variables in a camera body that it sounds unlikely to me that the sensor AND screen are automatically in their exact position after assembly. A difference of a few 0.01 mm's between the sensor plane and the screen and (manual) focus is sofar off you start seing it on the larger magifications. One way around this might be that Canon adjusts the mirror instead of the screen.

so he can
make the screens the proper thickness without the shim.

Still not a wise decision, IMO.

At least as of a few months ago I think he had determined that the
population of 350D/XTs out there actually had two shim values and

Toldyousotoldyouso! ;o)

Arjen.

 

[STFM]

The ones shipping now uses the shim. It's explained in a pre delivery e-mail. I don't know the reason, but that's how i is.

Mine was installed with the shim, and was supposed to be.

From mr. Haoda's website:

3. You do not need the copper shim for my screen. Keep the shim and
original in a safe place. You can change it back as long as you
wish.

I think it would have been much cleverer of Haoda to design his
screens with the existing shim in place. That way you always can
use his screen, no matter how far of the body is.

Arjen.

 

[STFM]

I paid $80 for over sea shipping.

It doesn't take long to to install, but you may need to adjust the screen a couple of times, as it's not falling into place as easily as the original screen. It has some slack, if you will, and needs to be properly aligned and as close to the prism as is possible. I'd say it takes anything between ten minutes and half an hour. If you do it again, it takes about a minute.

The ears (it's obvious when you see it) should be placed towards the lens, and the shiny side towards the mirror. That's important.

Hi there can you give us some indication of cost and the time
invioved in the installation.

Thanks in advance

Shane

 

[Arjen van Andel]

The ones shipping now uses the shim. It's explained in a pre
delivery e-mail. I don't know the reason, but that's how i is.

The reason would be that Canon calibrates their bodies with a (any) shim in place. If you remove it and the new screen is optically different from the original screen including the shim you have misaligned your camera, and would not be able to precisely manual focus anymore.

Arjen.

 

[Paul De Bra]

Instead of spending $80 on the Haoda screen I salvaged a focusing screen from an old film body that I could never sell for more than $50. I first tried with the copper shim but found that gave me massive front focus. I removed the shim and still had a bit of front focus. I filed down the thickness of the 4 sides a bit, and a bit more and a bit more, until I achieved perfect focus.

On my 300D the main mirror is not adjustable, so playing with the thickness of the focusing screen (with or without shim) is the only way to adjust the focus. It is amazing how small a variation in the thickness leads to how much of a focus shift. It's no wonder that obtaining acceptable focus with a 50mm f1.4 or f1.8 is so difficult. But with the split prism you can really do it.

Here is a sample shot, that AF just doesn't work with. It's taken with the 50mm f1.8 at f1.8. Dofmaster says that (at a distance of 2 meters) acceptable focus is within 5cm of the target, but to get perfect focus (1 pixel circle of confusion instead of over 2 pixels) it must be within 2cm of the target, meaning a margin of error of just 1%. With the 50mm f1.8 you don't have Af motor steps that are small enough for that.

full size: http://wwwis.win.tue.nl/~debra/photos/divers2005/orig/Image229.jpg



--
Slowly learning to use the DRebel (only around 20.000 shots)
Public pictures at http://wwwis.win.tue.nl/~debra/photos/

 

[kenw]

Haoda has found that the vast majority of cameras all have the identical shim installed

Hmm, that doesn't sound good to me. There are so many variables in
a camera body that it sounds unlikely to me that the sensor AND
screen are automatically in their exact position after assembly. A
difference of a few 0.01 mm's between the sensor plane and the
screen and (manual) focus is sofar off you start seing it on the
larger magifications. One way around this might be that Canon
adjusts the mirror instead of the screen.

I agree, but apparently for a number of cameras it is almost always the same. Canon could adjust the mirror, but they don't. The viewfinder mirror stops are fixed on the 300D, 350D, 10D, and 20D to the best of my knowledge. The secondary AF mirror, however, does have an adjustable cammed mirror stop for trimming the distance to the AF sensor.

so he can
make the screens the proper thickness without the shim.

Still not a wise decision, IMO.

Well, yeah, but if it makes it cheaper...

At least as of a few months ago I think he had determined that the
population of 350D/XTs out there actually had two shim values and

Toldyousotoldyouso! ;o)

--
Ken W
Rebel XT, DSC-S85, and a whole lot of 35mm and 4x5 sitting in the closet...

 

[Arjen van Andel]

Haoda has found that the vast majority of cameras all have the identical shim installed

Hmm, that doesn't sound good to me. There are so many variables in
a camera body that it sounds unlikely to me that the sensor AND
screen are automatically in their exact position after assembly. A
difference of a few 0.01 mm's between the sensor plane and the
screen and (manual) focus is sofar off you start seing it on the
larger magifications. One way around this might be that Canon
adjusts the mirror instead of the screen.

I agree, but apparently for a number of cameras it is almost always
the same. Canon could adjust the mirror, but they don't. The
viewfinder mirror stops are fixed on the 300D, 350D, 10D, and 20D
to the best of my knowledge. The secondary AF mirror, however,
does have an adjustable cammed mirror stop for trimming the
distance to the AF sensor.

For AF it makes no difference whatsoever, even if you mounted the screen upside down. But for MF to be succesful the screen has to be precisely positioned. Very precisely, in the order of a few 1/100 mm or less.

so he can
make the screens the proper thickness without the shim.

Still not a wise decision, IMO.

Well, yeah, but if it makes it cheaper...

But there are no expenses for Haoda; the shim is part of the camera, that's where it is calibrated with, and it should stay in place. Unless Haoda supplies you with a stack of shims and you have to calibrate the thing. Far easier would it be to produce these screens with the same offset the Canon screens have, then there's no hassle at all.

At least as of a few months ago I think he had determined that the
population of 350D/XTs out there actually had two shim values and

Toldyousotoldyouso! ;o)

--
Ken W
Rebel XT, DSC-S85, and a whole lot of 35mm and 4x5 sitting in the
closet...

 

[Doug Kerr]

Hi, Arjen,

Haoda has found that the vast majority of cameras all have the identical shim installed

Hmm, that doesn't sound good to me. There are so many variables in
a camera body that it sounds unlikely to me that the sensor AND
screen are automatically in their exact position after assembly. A
difference of a few 0.01 mm's between the sensor plane and the
screen and (manual) focus is sofar off you start seing it on the
larger magifications. One way around this might be that Canon
adjusts the mirror instead of the screen.

The mirror is only adjustable in one degree of freedom, and that is its angle when in the "viewing/focsuing" position. That needs to be set for proper registration of the viewed and taken images and so you can't use it for viewfinder focus adjustments (although people try to do that) - trying to do so messes up the registration.

Canon makes the adjustment by putting in one of several shims that exist (there are 11 that are listed in the parts book - 0.030 mm to 0.350 mm), although it sounds as if a couple of them get all the usage.

Best regards,

Doug

Visit The Pumpkin, a library of my technical articles on photography, optics, and other topics:

http://doug.kerr.home.att.net/pumpkin

'Make everything as simple as possible, but no simpler.'

 

[Doug Kerr]

Hi, K,

Haoda has found that the vast majority of cameras all have the identical shim installed

The secondary AF mirror, however,

does have an adjustable cammed mirror stop for trimming the
distance to the AF sensor.

It's actually for trimming the position of teh spot that each of the AF detectors regards. It also changes the distnce to the AF sensors, but not consistently for all of them, and I don't think it is intended to do that dury as well as its other purpose. (People of course keep doing that; I assume they have no idea where in the frame their AF detector end up regarding.)

so he can
make the screens the proper thickness without the shim.

Still not a wise decision, IMO.

Well, yeah, but if it makes it cheaper...

Note that the shim is also the assembly retainer for the indicator plate (has the AF "rectangles" on it in the 10D and 20D), and helps prevent that from falling out when the focusing screen is changed.

Best regards,

Doug

 

[Doug Kerr]

Hi, Arjen,

The ones shipping now uses the shim. It's explained in a pre
delivery e-mail. I don't know the reason, but that's how i is.

The reason would be that Canon calibrates their bodies with a (any)
shim in place. If you remove it and the new screen is optically
different from the original screen including the shim you have
misaligned your camera, and would not be able to precisely manual
focus anymore.

Also note that the shim is the assembly retainer for the indictor plate (carries the AF "rectangles" in the 10D and 20D) and keeps it from falling out when the focsuing screen is being changed.

Best regards,

Doug

 

[Doug Kerr]

Hi, Paul,

Note that if the focsuing screen is out of position, its effect on the plane of proper focus at the object is larger than the distance the screen is out of place by approximately the factor:

(P/f)^2

where P is the distance to the object and f is the focal length of the lens.

Thus, if we have a focal length of 100 mm and are focused at a distance of 10 meters, then an misplacement of the focuing screen of 0.01 mm will cause the object plane of focus to shift by about 100 mm!

No wonder Canon has shims whose thickness varies by 0.002 or 0.003 mm steps over most of their range (11 shims altogether).

Best regards,

Doug

 

[haoda]

I have changed the design for some cameras.
Thanks Doug.

Haoda

--
Haoda Fu
Haoda Split Image Focusing Screen On Canon DSLR
http://groups.yahoo.com/group/screen4DSLR/

 

[haoda]

By the way, I would like to point out. The Canon
use shims only with 0.05mm incresements. And
although they have 10 size screens, most of time
9 of them are backup. you will NEVER see them.

Also, some advanced camera DO NOT have shims. like 1D seriers and 5D.
why canon use shim on non-FF camera is still not fully answered.
It can not simply explained by adjustment!

Haoda Fu
Haoda Split Image Focusing Screen On Canon DSLR
http://groups.yahoo.com/group/screen4DSLR/

 

[haoda]

A good point.
But if 99.9% camera are using the same shim and
we can make a screen thick enough to accommdate
the thickness of the shim. There are big advantages
of the screen which do not need the shim. You know, the
shim is easily to be bend a little during the installation.
If it is bend, it will influence the focusing and the customer
can not repair it anymore.(at least it is very difficult to make
it perfect flat). The screens not requiring the shim
does not need to be bothered by this.

Again, I apprecaite your guys's helpful discussion.

Best,
Haoda
--
Haoda Fu
Haoda Split Image Focusing Screen On Canon DSLR
http://groups.yahoo.com/group/screen4DSLR/