How I fixed my front focus

great job MGW172!! I can't believe how many people are arguing with you when you have the camera in your hand, used and tested and it works yet they say you couldn't have fixed it. Keep us updated if you see any problems the emerge over the next couple times you shoot.

MGW172 wrote in post #3508599
To Adas- Not sure about the too smart woman comment - since I'm a guy! The avitar is my beautiful wife if that is where that is coming from.

Darn...I was really hoping you were one of us showin' up the boys around here. Oh well...

deadpass - I'll be sure to let you know the second it disentergrates in my hands - or any other problems I find.

Nanboh - don't worry, my wife might not know the inner workings of a camera but she'e really good at fixing the inner workings of people (and showing up most guys while doing it.)

MGW172 wrote in post #3508599
JackProton - I used the on board flash, which did not fire any bursts for focusing. Focusing was done only with light from a lamp located above the test target. Actually, the flash was only because I was annoyed at the poor white balance with incandesent lighting and I wanted to see a white page with black lines.

As for your second point - wow I dont know! Actually I wish I knew more about this and what exactly I was moving ect........

To Adas- my results show different than your statement and I did test for this. I wondered if I was shifting away something from the visible focus markers and I didn't. Not sure about the too smart woman comment - since I'm a guy! The avitar is my beautiful wife if that is where that is coming from.

Also all the focus points focus consistantly with no back or front focus, including the top points.

All I can say is your mileage may vary and maybe the problem with my camera was with this adjustment and nothing else.

Is it not more likely the actually sensors are being moved, perhaps up / down NOT the focus mirror - christ it would be a pretty impressive mechanism to get that screw to adjust the focus mirror and not the primary mirror!

ok, i did my 10D tonight after taking some pics where a few shots today were clearly off-focus. i didn't have my sturdiest tripod here so it's probaby not 100% right but it alot better now.

the OP's instructions were very good. i used some lens paper folded over to cover the sensor & protect everything. I HIGHLY RECOMMEND THAT. if you do this you'll want to dremel/grind down TWO 1.5mm allen wrenches so you can go always be able to make the adjustment.

holy gutsy move batman!

well done and glad it paid off....

chinch wrote in post #3510746
i used some lens paper folded over to cover the sensor & protect everything. I HIGHLY RECOMMEND THAT.

I hope you meant cover the SHUTTER and not an exposed sensor. You don't have to activate the shutter to get the mirror up, just gently raise it (I did it with one finger) and then use a small piece of tape to keep it up (see the second picture in original post). However, it is also probably a good idea to at least do a dust removal of the inside of the mirror box each time you go inside it.

On the tools required to adjust focus:

I just did a quick check on my 30D - the standard hex wrench size of .050" seems to fit perfectly. My length conversion software says that is 1.27mm. It inserts fully and I can turn it either direction. Now I have to adjust it because I moved it!

This may make things easier. But also easier to mess up. Be careful.

Rodney

I am looking at the mirror box a little more closely.

On the 30D it looks like there are adjustment screws on both the left and the right. All the comments seem to be about the one on th right. Has anyone done anything with the one on the left?


It looks to me like each adjustment screen will change the position of the secondary mirror slightly. If only one side is adjusted, the secondary mirror might be slanted slightly, which would mean different focus at different sensors. This could explain the different results people have reported - if you adjust the right side and that is what was needed, you may get great results. If you needed adjustment on the left side and you adjusted the right side, results would vary.

Also, on the 5D, there are 4 adjustment screws, 2 in the rear for the secondary mirror and 2 in the front for the primary mirror. So the two in the mirror adjust AF acuracy, the two in the front adjust the focus accuracy you see in the viewfinder.

On the 30D the screws for the primary are replaced by what look like plastic pegs, so the viewfinder focus accuracy on the 30D is not adjustable.


So, has anyone adjusted the screw on the left on any of the models - looks exactly like the screw on the right?

I can't find the link right now, but don't touch that screw on the left side. I don't remember exactly what it does, but I do remember it not being used for this procedure. The information is out there on the web somewhere and I remember there is actually a picture of the mirror box with both screws labeled.

For what it's worth, I didn't and never would just start turning screws without some information from other sources about this. Of course that information could have been unreliable, we are talking about the web ya know! Like I said in the original post, I got information from a couple of other sites before I tried this. Again....if you try to do this, procede at your own risk.

This just happened to work for me and I'm kind of a risk taker when it comes to tinkering. But if you want the safe route to getting your focus adjusted.....send it to Canon!

MGW172 wrote in post #3515253
But if you want the safe route to getting your focus adjusted.....send it to Canon!

OTOH, if you're gonna send it to Canon, might as well screw with it first and see what happens!

-js

Thanks for this post MGW172 (your parents must have hated you) you may have just saved me £150.

Worked a treat, all lenses now 100% perfect. Fiddly job on a 350d though.

IT WORKS!
I know that I said never try this at home, but I have an important shoot this week and no time for sending it in to Canon (not that this would ever be a pleasant option anyway). So I've tried that.
It's two weeks since I've bought the 200L and the sharpness just couldn't blow me away the way I expected at f/2.8. And yeah, it was a bit of front focusing (with all lenses).

Some interesting observations:
- It's not one screw, there are screws on both sides
- Both screws move simultaneously
- Apparently, the hollow facets are shifted one screw from another (possibly for allowing the adjustment with the same key, alternating among the screws)
- They are not simple screws, they're cam shafts (further evidence of their purpose)

Directions:
- Front focus: Turn the Right Screw Cwise (or Left Screw CCwise)
- Back Focus: Turn the Right Screw CCwise (or Left Screw Cwise)

Hello Everyone:

I'm new here and purchased a used 10D off Ebay about 6 months ago. The price was right and the camera mint! However, focus never seemed right with my 50 f1.8 and various lenses at my local camera store produced soft images that clearly were out of focus. After reading many posts about 10D focus errors, I was afraid I purchased an expensive paper-weight! Portraits of a friend weren't even in focus in bright sunlight at 5'. Focus tests showed a front focus of at least a cm. What I noticed however is that the focus error would grow as the distance to my subject grew. Landscape shots were clearly blurred despite bracing the camera and shooting at wide aperatures and fast speeds.

Long story short...I did some research and found a lot of information on focus correction for Nikon's D70 and D50. Canon's and Nikons DSLR's are designed on the same principles so I applied the technique as MGW172 described...Now my 10D focuses perfectly! Razor sharp even when pixel peeping.