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-   -   Dynax 7D - is "back focus" problem solved? (

Wojtek Oct 3, 2005 6:02 PM

I would like to ask for the "back focus" problem in 7D. Is it true that cameras released with the series number 92xxxx or higher have that malfunction fixed? I want to buy 7D soon, so it is very important for me to know how to choose the right camera.

JimC Oct 3, 2005 6:14 PM

I don't know about the serial numbers.

I personally wouldn't worry about it.

Even if you get one that has this problem, turnaround time from KM has been pretty good, at least here in the U.S. (some users have been reporting it only took about a week here in the U.S.).

Also, you can adjust it yourself if you need to. There are 3 hex screws under the piece rubber at the bottom of the camera by the tripod mount that control AF sensor alignment. So, you *could* set it up on a tripod with a good test target, and turn the screws until it's sharp.

Using CD or DVD cases arranged side by side (with cases on one sideof the middlecasea littlecloser to the camera, and ones on the other side moving further away from the camera) seems to be a popular method.

There are test targets you can print designed to do this kind of thing, too.

Users I've seen reporting they did it themselves say it only takes about 15 minutes to adjust it while taking test photos, with only 1/4 to 1/2 turn clockwise of the 3 hex screws correcting it.

If I bought one of these models, I'd probably "fine tune" it myself anyway (even if it didn't really need it). KM may not like it for warranty purposes (but I wouldn't tell them I did it).

Most of the time, owners don't even see it unless using a brighter lens at larger apertures and closer ranges (where Depth of Field is very shallow). Although I guess I have seen some reports of them being a little further off (where it may be noticeable using other lenses at further ranges, too). KM uses a 50mm f/1.7 to calibrate them when someone sends in one with a BF issue.

Wojtek Oct 3, 2005 6:29 PM

Thank you for your answer!
I have to say that it's a wonderful method. I've never heard that before. I am from Poland - here the hunderts, maybe thousands of users have sent their cameras to KM service to fix the problem. I only wonder whether the adjusting done with your method could cause the loss of the warranty? Is KM service able to "catch" such an adjustement made by user?

JimC Oct 3, 2005 6:40 PM

I've seen it reported that the screws had awhite adhesive substance on them (probably to keep them from moving after the initial adjustment). I don't know how obvious it would be that they've been adjusted by a user, but you could probably find a similar white adhesive (you'd probably want to do this anyway to prevent any movement of the screws after they're adjusted).

The rubber by the tripod mount uses a bi-adhesive that users report works just fine for reattaching the rubber to the camera bottom (it stays sticky enough for the reattachment without additional adhesive).

The screws are adjusted using a 1.5mm hex driver (and user reports I've seen indicate that 1/4 to 1/2 turn clockwise will fix it, even for those with a bad problem).

Wojtek Oct 3, 2005 6:44 PM

Thanx! I have just put your answer on the Polish KM forum. I am very curious if they have similar experiences...

JimC Oct 3, 2005 6:49 PM

I've been interested in the KM DSLR models for personal use for a while now. So, I make it my business to try and find out anything I can about them, since I plan on getting a KM DSLRsoon. :-)

I'll probably go with a 5D instead (I'll be testingto see if I like it better than the 7D or not). Hopefully, the AF sensor alignment is just as easy to adjust with it, too (although I have seen very few problems reported with it's AF alignment so far).

JimC Oct 3, 2005 7:14 PM

Wojtek wrote:

Thanx! I have just put your answer on the Polish KM forum. I am very curious if they have similar experiences...
Always do these kinds of things at your own risk (as Konica-Minolta might not like it for warranty purposes).

It sounds like the screws make a lot of change with very little adjustment (so, I'd be very careful and not turn them too much, making small changes until the BF is fixed if I were doing it -- making sure to turn them evenly so that I didn't end up with some AF points further off than others).

Again,users I've seen report fixing it said that it only took 1/4 to 1/2 turn clockwise of all 3 hex screws). So, a tiny adjustment apparently makes a big difference.


If you see anyone that tries it themselves in Poland. Let us know about here in this thread so that other KM DSLR owners (and potential owners) see some reports.


Wojtek Oct 4, 2005 4:27 AM

Users in Poland are extremely sceptic about that. I have just got the answer from one of the guys from the Polish forum:

"It's not a solution. I wonder how are you going to set ONLY the central sensor of AF? In my D7D there was the back focus on the vertical and horizontal sensors, but the other ones were correct. In such case you have no possibility to fix it...".

As you see, it is not so simple as many reported. I still have no 7D so I have no possibility to check it...

JimC Oct 4, 2005 6:23 AM

There are 3 screws, there is probably a reason for it (it's probably an AF sensor assembly mounted with them that could be getting tilted if the screws were not adjusted evenly from the factory). Also, you'll have focus plane differences at different points on a lens anyway.

That's one reason MTF charts show that lenses are not always sharpest in the center (often they are sharpest just outside of the center (the centeris at the left side of the graphs)at some focal lengths and apertures, and often the opposite is true).

Take a look at the MTF chart for a Tamron 35-105mm f/2.8 at 35mm and f/2.8as an example (I recently bought one of these used at a bargain price). It's sharpest just outside of the center at this focal length and aperture. So, it would be perfectly normal to see a difference between AF sensor pointsusing this lens. That's not a camera problem, it's a lens issue.

So, some cameras owners mistakenly think they've got a BF issue with some sensors, when they're only seeing a characteristic of a given lens. Use a good lens for testing. I've seen it reported that KM uses a 50mm f/1.7, with software looking at the sensor output while adjusting the screws. The computer shows a numeric reading so that they know when the adjustment is accurate. Using this technique (do it yourself), you'll need to look at test photos while making the adjustments.

There is also another hex screw that adjusts the angle of the light from the mirror, but users I've seen report trying it said that it had no impact on their BF problem--only the 3 screws at the bottom corrected it. But, there may be some exceptions as more owners test this solution.

I'm sending you a PM with a link to some reports of 7D owners that have fixed their cameras, including before and after test photos.

Everyone I know that has actually tried it so far say that it works.


I sent you the comments from 3 owners of the KM 7D that fixed their cameras, along with links to before and after photos. Note that some members say their problem apparently was being caused by the white adhesive not being good enough, allowing the screws to come loose (and some users said their adhesive had come off entirely)

So, this entire issue looks like itmay havebeen caused because the adhesive wasn't good enough (probably due to temperature and humidity changes)to keep the screws from moving. Siince we are seeing backfocus versus front focus issues, the screws on the bottomare probably slowly backing out when this happens (with clockwise movement of the screws fixing it). :-)

If you findowners that try it,make sure to update this thread so that other 7D owners (and potential owners) are aware of any pros and cons of this solution.


1958fury Oct 4, 2005 11:46 AM

Just so we're all clear. What exactly is "back focus", and what's an example of a back focus problem.

I love my 7D to death and it has performed perfectly since purchasing in 2/05. I will say though, my pics don't seem quite as sharp as my Canon Rebel.:O But I'm not sure this is the "back focusing issue" you guys are talking about.


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