Focus calibration - zooms! Creative Live is giving free live views of some of their courses. In a current one the instructor discussed lens focus calibration for fine-tuning on cameras...

Ranjan Loc: Currently Cyber-Nation!

Creative Live is giving free live views of some of their courses. In a current one the instructor discussed lens focus calibration for fine-tuning on cameras that have that feature as a user-selectable function.

For prime (unifocal) lenses this is easy to follow, but what happens with zoom lenses? Would the calibration (using a slanted and one vertical ruler or similar test-objects) need to be performed at both extremes of the zoom (and a mid-focal length for good measure?) or just one setting (which end of the range of the zoom?) would do?

For example, when performing it for a 24-85 mm zoom for an FX camera.

Would greatly appreciate hearing from UHH members who have performed such a calibration (this or any other zoom lens).

oldtool2 Loc: South Jersey

Ranjan wrote:

Creative Live is giving free live views of some of... (show quote)

Some cameras allow you to do micro adjustments at the wide-angle and telephoto end of the lens. On other cameras where you can only do one per lens they recommend you do it at the lens length you normally would use it at, in other words 60 mm might be where you use the lens most.

Other lenses and camera combinations allow you to do five or six micro adjustments. It all depends on what you need.

Jim D

MT Shooter Loc: Montana

Ranjan wrote:

Creative Live is giving free live views of some of... (show quote)

For zooms I always recommend tuning the focus at the focal length you use it at the most.
Some cameras allow two focus tuning settings, usually one at each end of the zoom. Those cameras then average the two settings and apply that average setting to the whole focal length.
Sigma lenses are unique to the market in that they allow the user to tune the lens' focus at up to 5 different focal lengths. This is only available on their newer Global Vision series lenses (S, A, C) but allows the user to do the tuning at home on your own computer, via their USB Dock. Be aware this process actually tunes the LENS itself, and has no effect on the settings of the camera you use it on.
No other manufacturer has released control of the focus tuning of their lenses, choosing to keep that process a secret and make you send the lens back to them to get this service.

oldtool2 Loc: South Jersey

MT Shooter wrote:

Sigma lenses are unique to the market in that they allow the user to tune the lens' focus at up to 5 different focal lengths. This is only available on their newer Global Vision series lenses (S, A, C) but allows the user to do the tuning at home on your own computer, via their USB Dock. Be aware this process actually tunes the LENS itself, and has no effect on the settings of the camera you use it on.

MT,

Thank you for this information, you just answered a question I was going to ask you. I was curious as to whether it affected the micro adjustment setting in the camera itself, now I know.

Jim D

Ranjan Loc: Currently Cyber-Nation!

Thanks OT2 and MTS for your help.

Rich1939 Loc: Pike County Penna.

When I fine tuned my lenses I checked the zooms to see what adjustments would be needed for both ends of their lengths. Fortunately in my cases the adjustments were not extreme. I opted then to make the adjustments on the long or max end of the zoom reasoning that at the short end (in your case, 24) the increased depth of field would help to compensate.

Ranjan Loc: Currently Cyber-Nation!

Rich1939 wrote:

When I fine tuned my lenses I checked the zooms to see what adjustments would be needed for both ends of their lengths. Fortunately in my cases the adjustments were not extreme. I opted then to make the adjustments on the long or max end of the zoom reasoning that at the short end (in your case, 24) the increased depth of field would help to compensate.

Thanks! This is a valuable addition and good advice!!

cjc2 Loc: Hellertown PA

MT Shooter wrote:

For zooms I always recommend tuning the focus at t... (show quote)

As Carter stated, this whole process is so much better on a newer Sigma. It is also a bit more work, but worth it in my opinion. Since I am new to both the Sigma concept and the ability of my Nikons to accept these settings I am guessing that I might find some adjustment that can be made to the body as a base adjustment after I complete this process which I am a long way away from. I am hoping that will allow better camera focusing overall, but will have to wait to see. As I suspect that at least one of my existing lenses has an issue, I suspect this process might lead to that lens going in for service. Only time will tell, but I expect to both learn and benefit from this whole process. As an aside, I have also found some software which claims to automate/semi-automate this process and I'm thinking of experimenting with that. If nothing else, this process convinced me to purchase Nikon Control 2!

oldtool2 Loc: South Jersey

cjc2 wrote:

As Carter stated, this whole process is so much be... (show quote)

I would recommend doing any adjustments on the camera first, then doing the lens.

I have used a program called FoCal with good luck doing my micro adjusting on my Canon cameras. I forget what it costs offhand but it is a very good program and would do your micro adjusting automatically for you.

Jim D

MT Shooter Loc: Montana

oldtool2 wrote:

I would recommend doing any adjustments on the camera first, then doing the lens.

I have used a program called FoCal with good luck doing my micro adjusting on my Canon cameras. I forget what it costs offhand but it is a very good program and would do your micro adjusting automatically for you.

Jim D

Jim, just so you are aware. Any adjustments made in the camera will be negated by adjustments made afterward in Sigma lenses.

oldtool2 Loc: South Jersey

MT Shooter wrote:

Jim, just so you are aware. Any adjustments made in the camera will be negated by adjustments made afterward in Sigma lenses.

Alright, I learned something else new today. I assumed that any adjustments made in the camera would be the starting point for the lens. So what you are saying is that the lens takes over completely as far as micro adjustment goes, correct?

You need to start giving instruction lessons for Sigma lenses. I still think your a representative for Sigma. LOL!

I really appreciate what you have been able to teach us about Sigma lenses, thank you.

Jim D

MT Shooter Loc: Montana

oldtool2 wrote:

Alright, I learned something else new today. I assumed that any adjustments made in the camera would be the starting point for the lens. So what you are saying is that the lens takes over completely as far as micro adjustment goes, correct?

You need to start giving instruction lessons for Sigma lenses. I still think your a representative for Sigma. LOL!

I really appreciate what you have been able to teach us about Sigma lenses, thank you.

Jim D

This is correct, the camera adjustments do not take into account any of the adjustments to the lens. Any brand lens besides Sigma does not allow the end user to adjust the lens' focus at all, so the camera body is the only means of doing so. I truly believed this was ground breaking technology when Sigma introduced it, and still do. I only wish the other manufacturers would all make software available for doing the same thing with their lenses. The Sigma USB Dock would easily work with any of them and make it a universal interface device for all lenses (you would need a different Dock for each camera mount obviously).
This would make EVERYONE capable of getting much sharper images with their existing gear.
Someday................ ;-)

ballsafire Loc: Lafayette, Louisiana

Here is a free for all question concerning calibration of lenses: Why would I want to calibrate my lens? Is it defective? If it is what's the use?

MT Shooter Loc: Montana

ballsafire wrote:

Here is a free for all question concerning calibration of lenses: Why would I want to calibrate my lens? Is it defective? If it is what's the use?

Design tolerances can vary between lenses, even of the exact same model. While these variances are minimal, the lens to sensor distance is so critical that if a lens is at one end or the other or the acceptable tolerance window, you may not be totally happy with the sharpness of the resulting image. Better quality camera bodies all allow for the end user to "Tune" the AF point of that camera to the particular lens in use.
Its actually a very simple operation once you learn how to do it, and each photographer whose camera has that capability definitely should take the time to at least TEST each lenses AF accuracy so he or she KNOWS what that lens is focusing on. Adjustments can be, and usually are, quite minimal, but can make a very noticeable difference in image sharpness and overall quality.

Rich1939 Loc: Pike County Penna.

MT Shooter wrote:

Design tolerances can vary between lenses, even of... (show quote)

In addition as you use your camera and swap lenses sooner or later the wear on the mount can affect focus settings, as can silly things like temperature changes. Not to any great magnitude but over time the various things that can alter the original setting can add up and may require you to re-tune your focus settings.