conurus

[conurus]

With the advert of the AF micro-adjustment feature of the latest Canon 1D mark III camera, I do not need to hide this undocumented feature any longer.

If your lens was converted after 2007/01/01, you already have this feature. You may store an AF adjustment value in the non-volatile memory of the conurus chip to correct focus accuracy issues. If your lens was converted before that, a firmware update is available for the cost of shipping both ways.

Having this feature built into the lens means it is available to all camera bodies, not just the newest 1D mark III. For zoom lenses, there is a difference between the two, however. 1D mark III lets you store one adjustment value which applies across the entire zoom range. Canon recommends adjusting at the tele-end because that is more likely to run into focusing issues. A Contax N-series lens converted to EF mount lets you set a different adjustment value for each focal length. Please zoom to these focal lengths and make adjustments for each of these individually. It will affect the nearby focal lengths as well.

20mm
28mm
35mm
50mm
70mm
100mm
140mm
200mm
300mm

Use this web-based tool to make AF microadjustment easier. Just punch in the serial number of the lens, choose whether you want to adjust infinity, closest focusing distance, or the entire focusing range, and punch in the adjustment value. It will generate step-by-step instructions for you.

http://en.conurus.com/afmicroadjustment.php

[jjlphoto]

Conurus-

So if I want to attempt to move the len's focus away from me, do I guess at one of the positive values, or should I start with the 1 first, do a test, and if not satisfied, then try 2, etc?

Just so I understand the chart properly (it's been a while since college algebra) the bold numbers on vertical column on the left edge is my camera's aperture dial setting, and the bold numbers on the horizontal column on the top is my Contax lens's aperture ring setting?

[conurus]

Yep, bold numbers in vertical column are camera aperture values and bold numbers in horizontal row are lens aperture values.

Please try the largest value first because a change of 1 is hardly noticeable. If it overcorrects, then halve the adjustment value and try again.

[plog1964]

Conurus -

Thanks for this wonderful new feature. The instruction provided is too short and lacks some important details.

(1) As I see steps 1-7 is like a code sequence to enter into adjustment mode. How can I guess I have correctly entered into the adjustment mode? Any blinking dots or some other indication in the viewfinder?
(2) How can the lens chip figure out the focus length the adjustment should be applied for? Do I have to set the focus length before executing steps 1-10 in your instruction? Do I need to repeat steps 1-10 for each focus length separately?
(3) How can I enter adjustment values. Should I use the dial on the camera body?
(4) Do the tables show the current (default) adjustments initially written into the chip?
________
Earthquake insurance dicussion

[jjlphoto]

plog-

It appears that steps No. 1 through No. 6 prepare the lens for this procedure.

When you get to step No. 7, set your camera aperture and lens aperture ring to the f numbers by your desired adjustment value.

For example, my 100 Makro Sonnar was planting actual focus in front of the desired subject, so I chose to try adjustment value 21 for my lens. At step No. 7, I set my camera's aperture to f/4, set lens' aperture ring to f/4 because that is what the chart reads for an f22 type lens.

I then proceeded to step No. 8. It seems that the act of depressing the DOF button as indicated "enters" the function into the chip.

I then continued to steps No. 9, and No. 10. (No. 9 & No. 10 appear to close the procedure.)

For a Contax zoom, it apperas that you do this for each of the listed focal lengths. I guess there is not one for 17mm position (for those who have that zoom).

Boy- I sure hope you don't have to do this for various distances. That could take a while to do. My understanding is that the position of the lens barrel focus distance has no effect on this procedure, but let's have Conurus verify that.

[conurus]

Steps 9 to 10 means, "Yes, I am sure" and confirms the writing of the adjustment value into non-volatile memory.

Yes, you zoom to each focal length and set adjustment values for each focal length independently. For 17-35, the focal lengths to adjust are 20mm, 28mm and 35mm.

It is a good idea that we could use some feedback to the user that he/she has successfully entered the adjustment mode, and also to add a way to read the adjustment value already set. I will try to incorporate these into a future version of firmware.

Focus accuracy has always been a hot topic among Canon users and that's why I have always taken this very seriously. I gathered a large amount of measurements and analysed them with statistical methods. I also tried different Canon bodies and found them to be remarkably consistent, a stark contrast to the general perception (IMO mistaken) of inadequate QC - and this is only for consumer-level Canon camera bodies.

In the field, it is not easy to get accurate AF under changing conditions. The AF zone is much larger than indicated, confusing a lot of users. If there are multiple objects in the AF zone, the camera may pick any one of them and you wouldn't know or understand what the camera does. You are very likely to fail to notice anything wrong here because those objects may be outside the 'square' but nevertheless sensed by the AF. If you try to focus on extremely fine details, aliasing effects may confuse the AF sensor and mislead it into making totally wrong decisions. Handholding means you may rock back and forth after AF locks and change the focusing distance (this is a significant phenomenon for the N-Planar 85/1.4).

But in a controlled experiment, the AF shows very high accuracy. Just try a few adjustment values using the AF micro adjustment feature, shoot the same scene, wide open, and near the closest focusing distance for reduced depth-of-field and see which adjustment value leads to the sharpest pictures. It is zero most of the time if your lens is equipped with the latest firmware version.

[mOnAmis]

Will this feature work on the 85mmf1.4? Will it work throughout the entire focusing range?

[conurus]

Yes, 85/1.4, too. Any lens modified after 2007/01/01 would have this feature. If you are unsure, type your lens' serial number at

http://en.conurus.com/track.php

and if the firmware version is 1.10, then you have this feature.

The same adjustment value applies throughout the entire focusing range.

[mOnAmis]

Conurus
Which code is it for 70-300 and which one for 85? 065 or 102.

Thanks

[MomoInu]

you probably need one more potential answer in your poll:

"I don't have an AF accuracy issue, but would like to see this feature just in case I ever do."

That would get my vote.

[conurus]

[conurus]

Based on customer feedback, visual confirmation is added to the AF adjustment. Also to safeguard against accidentally entering the adjustment mode, you would now need to manually focus the lens to minimum focusing distance throughout the adjustment procedure.

[jjlphoto]

If I am doing an AF micro-adjust to a zoom, can I approximate the zoom positions based on the len's zoom ring, or do I need to use exif data to make sure the lens is "exactly" at 20, 28, 35, etc?

[conurus]

No it does not need to be exact. The markings on the zoom ring are good enough, and pretty accurate actually.

I use this focus accuracy chart and I highly recommend it.

[cbowman]

Conurus: As I understand this thread, although I have the software for making adjustments, I do not need to due to the date the conversions were performed. Is this accurate? Thank you. Curtis