Fine focusing/calibrating lenses

[mongo]

This is just a very quick mention about an aspect of fine tuning the focus of your lens to your camera body which many of you may already know. Mongo will mention it just quickly for those who may not.


When you fine tune the focus of any lens on camera bodies that have this facility, it is NOT enough to do it to the bare lens alone if you also intend to use it with converters.


Simple example, the Nikon 300mm f4 AFS Mongo tested and posted recently in this forum had NOT had an auto focus fine tune carried out on it at that time. Mongo reported excellent sharpness for the bare lens and also with the 14EII converter BUT said the lens did NOT work well with the 20EIII converter. That last finding proved to be very INCORRECT. The lens does in fact work extremely well with the 20EIII.


It was not enough to tune the bare lens.


Since then, Mongo has fine tuned the auto focus. Mongo did the auto focus tuning for the bare lens and each combination of the lens with different converters. Logically, adding any other lens glass to a bare lens (like a converter) changes the characteristics of that lens/converter combination. The camera sees the lens and converter combined as a new or different lens - and indeed, it may well have different optical characteristics as a result.


To illustrate the differences, the adjustments needed were as follows:-


+4 for the bare lens,
+9 with the 14EII converter,
-15 with the 20EIII


With such a large adjustment difference to achieve spot on focus, it is no wonder that the original (uncalibrated lens) results yielded very poor outcomes for the 20EIII which in real terms, required over 20 points adjustment (at least 15 of which were in the opposite direction). The results are now very sharp for all three scenarios mentioned above.


So, for those who have not fine tuned the focus of their lenses (and have that ability on your camera body), .......what are you waiting for ???


For those of you have just fine tuned the bare lens but may use converters, you need to fine tune every combination separately if you want results. Your camera does not mind. It happily stores each combination separately and call it up an applies those adjustments every time you pop the lens on and have the AF turned on.

[godzhitman]

I just calibrated my lenses on the weekend, I can't believe I've been shooting for years and never thought about it. Definitely beneficial. Thanks for the reminder re: extenders...I gotta redo it with one on.

[Stoodoo]

What is needed to calibrate a/f? I'd like to give it a try, but have no idea on what to do.


Cheers :)

[fess67]

I gave it half a go a year or so ago but maybe I got it wrong. The technique I was using was researched on the web and although it seemed simple on paper I found it difficult in practice and I think I made the issue worse. I still think I have a back focus issue but then again I look at my techniqu as being the issue because some images are crystal clear.

What technique did you use?

[mongo]

Mongo used 2 methods. Effectively, the second method was really to cross check the first method but any one method should be OK.

Consistency is all important when you are trying to tune such vey fine focus distances. Therefore, Mongo suggests you mount your camera and lens setup on a tripod and try NOT to move it for the duration of the testing/adjustments.

If you look on the net for various test chats for test focusing lenses, you can find an appropriate one to print off (usually in A4 size). One type of chart will be as simple as a ruler on paper . This is sep up tiled at 45 degrees to the camera/lens some distance away. The distance may often depend upon the focal length you are trying to fine tune e.g. Mongo's 200mm lens was set up at say 6 - 8 metres away from the test chart. Make sure you are on level ground as much as possible. Mongo did his tests on the tile floor from end of the sunroom to the other. The chat must also be set up to line up exactly with the hight of the lens i.e measure from the centre of the lens to the floor and make sure wherever you have set up the test chat (at 45 degrees) that the "0" point of the chart to centre of the chart is at the same distance to the floor as the centre of the lens was. Also make sure the lens and the chart are lined up laterally i.e. if you set up your camera/lens , say, 1.5 metres from the side wall of the room, make sure the centre of the chart is also set up 1.5 metres from that same side wall at the other end of the room . Basically , everything has to be squared up with the floor and the wall beside you.

then set you adjustments of the lens to "0" as your starting point. Open aperture fully. take some test shots at the "0" /centre of the test chart. When you review the result, the "0" should look the sharpest on the page/image. If the successive numbers closer to you look sharper than the "0" point, your camera is front focusing. In other words, you have asked it to focus on the "0" but it has chased instead to focus on a number which is closer to you which means it is focusing "in front" of where you asked it to. Vise vera if it focused behind the "0" point. go into your camera's fine adjust menu (which usually has adjustments of + or - 20) and either add or subtract , say, at increments of 2 and retest to see if you have to add or subtract more until the "0" point on the test chart looks the sharpest on the chart.

In the example above, if it front focused, you "add" fine focus in the menu (i.e. you will be telling the camera that it focused closer than it should have and to please "add" some distance and focus a little further away. Vise vera if it focused behind the test point on the chart.

another method was to print a test chart that has some fine detail on it with lots of squiggly things you will see when looking for chats - a little like bits and pieces of old TV test patterns. simple set this up parallel and squared off (as set out earlier above). take your test shots. If it looks really sharp - leave it alone and go and do some real photography. If not, adjust fine focus by adding or subtracting until the chart looks at its sharpest. The disadvantage with this method is that , initially, you do not know if you have to add or subtract in fine focus to start with but you will soon see if you are going the right way and if not just reverse your fine tune adjustments and start going the other way.

Sorry this is a little brief and had no time to include pictures or diagrams to help explain the above but there are a lot of articles on the net if you google for camera fine focus method etc.

[enseth]

I would assume this fine tuning going to vary from lens to lens. Is this correct?

[mongo]

I would assume this fine tuning going to vary from lens to lens. Is this correct?



YEP !

[ameerat42]

Ta mongo.

[mpot]

I recently bought a Sigma 35mm f/1.4 DG lens, and found the focus accuracy varied with focus distance.
Today, I bought the Sigma USB lens dock, as it allows you to specify micro adjustments for the lens at different focus distances - thus providing a whole lot more flexibility than micro adjustment in a camera body only, where a single adjustment covers all focus distances.

I haven't yet had a chance to calibrate my lens using the dock, but I think it's a pretty cool idea, and I wonder how long it will be before other lens manufacturers provide similar tools to allow you to update lens firmware, and/or re-calibrate a lens via your PC...

[mongo]

I recently bought a Sigma 35mm f/1.4 DG lens, and found the focus accuracy varied with focus distance.
Today, I bought the Sigma USB lens dock, as it allows you to specify micro adjustments for the lens at different focus distances - thus providing a whole lot more flexibility than micro adjustment in a camera body only, where a single adjustment covers all focus distances.

I haven't yet had a chance to calibrate my lens using the dock, but I think it's a pretty cool idea, and I wonder how long it will be before other lens manufacturers provide similar tools to allow you to update lens firmware, and/or re-calibrate a lens via your PC...


Big thanks Mpot. Mongo had forgotten about this great feature on Sigma lenses. It's almost never spoken about but is a very advanced form of fine tuning at all /most distances but only for Sigma lenses and only with the use of the specialised dock. Still, excellent technology and great idea.

PS please let us know how easy it is to do and how well it works after you have done it

[ktoopi]

I've wanted to do this since I got my 5diii as I have seen the facility to do it in the functions but had no idea where to start or what to do...I hadn't looked on the net as it seemed all too hard.....but now I will look it up and have a go! Thanks Mongo:)

[Speedway]

I found similar problems with my 70-200 F2.8L is II and the 2X III Extender. The Lens was spot on but the 2Xe was way off. I just set up a small red reflector on one of my front fence posts, the fence is an old woven wire mesh with about a 50h X 100v mesh, I set the camera on a tripod at an angle to the fence with the lens centre height at the same as the reflector and took a couple of shots, after about 5 sets of shots and the extender set at -16 I was happy with the much improved results.
Cheers
Keith.

[arthurking83]

......

..... and I wonder how long it will be before other lens manufacturers provide similar tools to allow you to update lens firmware, and/or re-calibrate a lens via your PC...

Too long I reckon, and almost certainly never(by some)!

If there's a wholesale move by a lot of people towards these types of accessories, then it will place pressure on other manufacturers to follow.

I'd prefer to see this level of programmability in the camera rather than the lens.

why? It's generally accepted that each lens will have slight tolerance differences with various bodies, and we know that lenses are generally dumb(only in that they don't know the camera attached, as the smart communication is only set the other way around .. camera knows the lens .. even down to a serial number!
So it makes more sense for the camera to tell the lens how to focus for certain distances, rather than the lens to set itself to focus in specific steps according to distance.

Setting the lens at a specified programming may cause the situation where it has slight focusing inaccuracies on different bodies(for those that use a single lens on various camera bodies).


Funnily enough, software does exist for re-setting the camera to focus in specific ways for individual focus points, but us mere mortals aren't (generally)allowed access to this software(unless you know someone that knows someone .. ;))

And from memory, the new Olympus OMD E M1 allows this sort of programming within the camera to a limited degree.
It allows fine tuning of individual af points, and for zoom lenses it allows af fine tune at the wide end and or at the tele end as separate values.
One of my biggest gripes with AF fine tune and zoom lenses.

I can imagine it being a tedious affair to have to set all these tweaks via the camera itself, so it'd be nice if the manufacturers had some sort of software available to allow this level of tuning by the consumer.


... anyhow ... all pipe dreams on my part.

My only use for AF fine tune now is simply as confirmation that my camera-lens combo has some issues that I should be aware of. I don't use it in every day usage.

[mpot]

PS please let us know how easy it is to do and how well it works after you have done it

I'm intending to post some info about my experiences with it when I get a chance!

[basketballfreak6]

I recently bought a Sigma 35mm f/1.4 DG lens, and found the focus accuracy varied with focus distance.
Today, I bought the Sigma USB lens dock, as it allows you to specify micro adjustments for the lens at different focus distances - thus providing a whole lot more flexibility than micro adjustment in a camera body only, where a single adjustment covers all focus distances.

I haven't yet had a chance to calibrate my lens using the dock, but I think it's a pretty cool idea, and I wonder how long it will be before other lens manufacturers provide similar tools to allow you to update lens firmware, and/or re-calibrate a lens via your PC...

the dock is great ain't it?

i myself just hand held and did quick and dirty ~10 min testing with my 35 1.4 and ended up something like +3 +3 +6 +3 and as far as i can see it's been pretty spot on since

rumour has it that they are going to update it to support some of their older lenses...hope it's true wouldn't mind putting my 85mm through the dock as well!

[danny]

Thanks mongo!!!! After reading this thread I fine tuned my lenses and am OVER THE MOON. I had been getting some what worried as my shots just seemed to be out of focus more than I would have liked. But after a quick fine tune last night it has made a world of difference.

Cheers
Danny

[richo]

I have been meaning to do this for a while. I think the time is right

Thanks
Adam

[mpot]

PS please let us know how easy it is to do and how well it works after you have done it

I spent some time using the Sigma USB dock to calibrate my Sigma 35mm f/1.4 DG lens, and ended up with these adjustments:
+2, -1, +3, 0
at 0.3m, 0.4m, 0.7m, infinity respectively.

I found it pretty straightforward and easy to calibrate the lens with the USB dock - albeit a little tedious, as you need to take some test photos at each of the focus distances (and for a zoom lens, this is done at each of 4 focal lengths), review the photos, remove the lens from the camera and connect it to the dock, run the Sigma Optimisation Pro software, want for it to check for updated dock firmware, and for updated lens firmware, then apply some adjustments, remove the lens from the dock and put it back on your camera, take some more test photos, and repeat until you are satisfied.

For more details on using the Sigma USB dock, and how I calibrated my lens, check out my blog post (http://martybugs.net/blog/blog.cgi/gear/Sigma-USB-Dock.html).

[mongo]

I spent some time using the Sigma USB dock to calibrate my Sigma 35mm f/1.4 DG lens, and ended up with these adjustments:
+2, -1, +3, 0
at 0.3m, 0.4m, 0.7m, infinity respectively.

I found it pretty straightforward and easy to calibrate the lens with the USB dock - albeit a little tedious, as you need to take some test photos at each of the focus distances (and for a zoom lens, this is done at each of 4 focal lengths), review the photos, remove the lens from the camera and connect it to the dock, run the Sigma Optimisation Pro software, want for it to check for updated dock firmware, and for updated lens firmware, then apply some adjustments, remove the lens from the dock and put it back on your camera, take some more test photos, and repeat until you are satisfied.

For more details on using the Sigma USB dock, and how I calibrated my lens, check out my blog post (http://martybugs.net/blog/blog.cgi/gear/Sigma-USB-Dock.html).


it was great to hear back from you after having done the exercise. That is a killer lens for sharpness and if you got it at its best now , it would be unbeatable. It was also good to get your honest feeling about doing the exercise with the Sigma system - yes, it is a bot of work no matter which system you use to calibrate the lenses but it is a one off and pays dividends for the rest of the lens' life on that camera body and as such, it is very worth while. Hope you enjoy the results.