ebay split focus screen? Should I? - and which one?

[-halli-]

I'm possibly considering one of the eBay focussing screens for my 400D, but I'm confused as to which to get.

What are the main differences in use between the single 45 degree, dual 45 degree and the single 180 degree variants?

Also, I realise the focus points will not be visible, and the flashing confirm lights won't appear in the image to say it is in focus, but will the confirm beep still sound?

I've read the tutorial on the Katzeyeoptics web site and it seems doable.

The reason for the possible upgrade is that I'm still having trouble with manual focussing and viewing through the viewfinder. I'm going to take the focus screen out and put it back in again this evening as I think it might have been bumped or something by its previous owner.

As I said in a previous post, when the AF focusses, the image in the viewfinder is blurred even though the LED display in the eyepiece is pin sharp - the resulting picture taken is in focus. When I manual focus I can get the image in the viewfinder pin sharp, but the resulting image is well OOF.

Adjusting the dioptre just makes the LED display go in and out of focus and makes the image in the viewfinder become less in focus each way. I therefore don't think it is an eyesight thing - as said, I can manually focus to make the image in the viewfinder pin sharp.

For most circumstances I just set to AF and click away. This is fine, but I am very interested in macro photography and it is becoming frustrating that I can't see when the image is in focus when using MF and the rocking method.

I've also just bought a retro 50mm prime (pentacon prakticar) which has MF but an AF confirm chip on the adaptor) and it is irritating that when the AF confirm says it is in focus, I can't see the image in focus in the viewfinder.

thanks in advance

 

[Canon Bob]

If you're intending to use it for general macro stuff (insects and alike) then I'd go for a single prism. If you intend to take close-ups of flat objects then the double will be a benefit.

The double prism, when used on a flat object like a coin, allows you to judge whether you are perpendicular to the subject as you'll only see compliance in both prisms when you are. The downside to double prisms occurs when the object is not flat. A rounded suface, or one that is not perpendicular, will satisfy one prism but not the other. Using the double, it's quite normal for the leg on an insect to be complete in one orientation but fragmented in the other....which one do you choose as being correct?

I have both options but only use the double when I'm trying to emulate a copy stand scenario.

HTH

Bob

 

[-halli-]

If you're intending to use it for general macro stuff (insects and alike) then I'd go for a single prism. If you intend to take close-ups of flat objects then the double will be a benefit.

Cheers Bob, that makes sense regarding the single and dual prisms. So what does the 45 and 180 degree mean?

 

[Canon Bob]

It's the orientation of the prism, simple as that. The singles I use are horizontal and the double is horizontal and vertical. A horizontal prism will not give accurate feedback on a horizontal feature (nor a vertical prism on a vertical feature). A 45 degree prism will allow you to focus on either a horizontal or vertical feature and still show the parallax error. The downside is that the potential accurracy is halved (although it will be better that the other two options if the feature is at 45 degrees in opposite quadrant to the prism )

Bob

 

[-halli-]

It's the orientation of the prism, simple as that. The singles I use are horizontal and the double is horizontal and vertical. A horizontal prism will not give accurate feedback on a horizontal feature (nor a vertical prism on a vertical feature). A 45 degree prism will allow you to focus on either a horizontal or vertical feature and still show the parallax error. The downside is that the potential accurracy is halved (although it will be better that the other two options if the feature is at 45 degrees in opposite quadrant to the prism )

Bob

Aha, right. I think I understand

If I'm taking a picture of one of my kids, full face and the camera is in the landscape position - which would be better? Likewise for portrait orientation of the camera.

Also, which prism would be more suited to everyday snapshots plus the macro I'm striving for?


I took out the focussing screen about 10 mins ago, cleaned it with my blower, put it back in and it is a little bit better - but not much. Could it be that it requires another shim/shim taken away? It only had one of the brass shims in place, so I guess that is how Canon calibrated it in the factory.

 

[Canon Bob]

Aha, right. I think I understand

If I'm taking a picture of one of my kids, full face and the camera is in the landscape position - which would be better? Likewise for portrait orientation of the camera.

Also, which prism would be more suited to everyday snapshots plus the macro I'm striving for?

I'm sure your kid's faces will have enough features running in any orientation for any single prism to be fully useable....(if not, draw some lines on them with a think felt markerpen )

I took out the focussing screen about 10 mins ago, cleaned it with my blower, put it back in and it is a little bit better - but not much. Could it be that it requires another shim/shim taken away? It only had one of the brass shims in place, so I guess that is how Canon calibrated it in the factory.

Shimming is certainly critical to get the best results. There's also another little problem that can occur (it did to me anyway). There's usually some soft compressive material when the screen mount clicks back into place. This may be slightly trapped and cause the screen to be slightly out of position and I only realised this when shots focussed using the bottom of the screen were different to those focussed using the top.

Bob

 

[-halli-]

Right, I've just done some rough tests to see if I can work out the difference between the AF (which is correct) and my manual focussing (which looks correct in the viewfinder but OOF in the pic)

Using my 50mm lens at f1.8 on a tripod with cable release

at 1000mm from subject to the mark on the body that denotes the sensor position

AF was in focus when the focus dial on the lens was lined up to roughly 1.20m

My focus in viewfinder was when the focus dial on the lens was lined up to roughly 0.81m

A difference of 39mm

--------
at 740mm from subject using the same lens

AF was 0.8m

MF was 0.68m

a difference of 12mm

----
at 510m from subject using the same lens

AF was at 0.54m

MF was at 0.47m

a difference of 7mm

Any ideas? As I say, the image in the viewfinder is pin sharp when I focus manually, but blurred in the viewfinder when AF is confirmed. I can get the viewfinder close using the dioptre control (it is around the middle) and I can blur the viewfinder on both sides of the dioptre meaning I'm not at the end of the dioptre's range thus requiring a corrector lens.

I'm stumped.

I'm posting this on the original thread too.

 

[-halli-]

Shimming is certainly critical to get the best results.

Is this something that would have to be done by canon, or would a photography shop be able to do it? (or is it something that could be done at home? Are shims available to buy?)

 

[-halli-]

well, I've bought one. single 45 degree variant.

Worth a punt for £14 so it should be with me within the next 4 weeks from China.

I'm going to have a go at beefing out the shim with some scotch tape with the current screen (I've been googling and it seems simple enough!)

Apparently the replacement screen is thicker than the standard anyway, so I'll have to see when it arrives.

At least I can still go back to the old one if I don't like the split one.

Thanks for the help.

EDIT: Not sure if you saw this that I posted on the other thread

------
Ok, did another experiment.

I took a photo through the eyepiece with my point and shoot.

Turned dioptre to bang on centre

with my manual focussing (but resulting photo will be OOF)

With AF confirm (resulting photo will be in focus)

I'm not sure if this proves anything though?

 

[Canon Bob]

Is this something that would have to be done by canon, or would a photography shop be able to do it? (or is it something that could be done at home? Are shims available to buy?)

Canon have shims (they call them washers!) for various bodies although I don't have part # for yours.

well, I've bought one. single 45 degree variant.

Worth a punt for £14 so it should be with me within the next 4 weeks from China.

I'm going to have a go at beefing out the shim with some scotch tape with the current screen (I've been googling and it seems simple enough!)

Apparently the replacement screen is thicker than the standard anyway, so I'll have to see when it arrives.

At least I can still go back to the old one if I don't like the split one.

Thanks for the help.

There is an equation for working out how much shimming you need (or need to remove) but it gets a little complicated as you need to know the exact focal length of the lens when recording how much front or back focus your screen is giving you. The focal length is not that recorded on the body (spec'd at infinity) or what the Exif might show.

Scotch tape should work and is certainly quicker than working out all the maths.

Bob

 

[-halli-]

Cheers Bob, I'm going to get some scotch tape tomorrow and will have a go with the current screen.

Washers! I've been searching for shims on google. No wonder I couldn't find anything!

 

[-halli-]

I installed the ebay split screen and I am amazed at the difference!

Sharp focus in the viewfinder, 45 degree prism works a treat and I can now use my manual focus lenses with ease!

I installed the viewfinder without the factory shim and it seems to have made all the difference. I never did try to shim up the old one, don't think I'll bother now!

Viewfinder is a little darker, and one half of the prism goes black if I try to focus with a lens stopped down past f5.6, but that is fine, I'll focus and then stop down if required.

I'm looking forward to testing it in anger tomorrow

 

[-halli-]

Focussed on the "N" in the eyepiece for this shot (No. 1 & 2 macro rings attached to my Prakticar 50mm 1.8 manual focus lens.

 

[R.Y.K. LEE]

This is with an Ebay focus screen? I was looking for a focus screen for the 7D and only found one in the US for about $100+ This is just the sort of thing I was looking for!

How did you find the quality of the Ebay focus screen, is it well made? Also, does the viewfinder get darker even with fast lenses or just using slower lenses (Like the effect with 5D mkII EG-s screens).

I noticed the product is in China, did you have to pay tax/duty on it? Thanks.

 

[-halli-]

Yes, a Travor 45 degree split screen from China. No import duty to pay, but did take about 2 weeks to arrive.

The screen is slightly darker in the main frame compared to the original screen at f1.8 but the centre circle and prism are bright. The prism darkens as aperture gets smaller and one half becomes black past f5.6

It looks good quality to me, came with "finger condoms" and two tweezers (metal set and plastic set) instructions and the screen.

 

[pearce_jj]

I changed my screen to the matt jobbie a while ago, which also improved manually focus with fast lenses. On the flip side it's only meant for 2.8 or faster glass.