Whats the most you would fine tune focus a lens before you decide to return it?
Hi, first post here.
I have just bought a second hand Sigma 70-200 2.8 II (non OS) and it is front focusing.
I payed £299 (they go for around £580 new here) and if i use the fine tune focus which is built into the camera i have to set it to +17 to get it about right (it goes to +20).
I have bought 3 of these lenses which i have got online before and everyone of them has front focused on my d90 and d7000 so i have sent them back. Is there a problem with most of the 70-200 sigma's or am i just unlucky? It isnt my camera as i have tried it on two of my bodies and even took it to a near by camera store for them to look at and it has happened on the bodies they use too.
Like I said, this one is £299 and i cant really afford to pay full price at the moment for a brand new one and it seems to be fine when i use the fine tune focus but i was wondering if +17 is too much to fine tune it by.
Should i stick with this second hand one and carry on using it with fine tune focus or should i return it and just save up and get a brand new one in a couple of weeks?
Thanks a lot
#1. "RE: Whats the most you would fine tune focus a lens before you decide to return it?" | In response to Reply # 0Len Shepherd Nikonian since 09th Mar 2003Tue 28-Jun-11 04:47 PM
Without seeing a link to an image it is difficult to comment.
On a detail lenses do not ordinarily front or back focus in the sense they use exactly the same information to AF as we use to judge when an image is sharp when using manual focus.
You can get a front or back focus effect if your body is out of alignment - which implies both your bodies might be out of alignment.
You can get a front of back focus effect if if your camera AF system cannot detect the AF subject well - Nikon include a whole section on this in camera instruction books and at https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/4585
You can get front or back focus with an AF-s type lens if their is a fault connected with the internal AF motor.
Some "blame" tolerances - lenses do sometimes have tolerances, especially if well used. However tolerances are normally random and may show opposite Fine Tune indications starting first at infinity focus and then at minimum focus.
The chances of 2 Nikon bodies and 4 lenses all have a focus issue in the same direction seem very low - and indicate the suitability of your focus target for calibration is worth investigating.
It is possible the Sigma has a fault which showed in the camera shop as well - but on 4 lenses something unusual is going on.
The difference between nil and 10 on the Nikon 70-200 is below. Having tested over 100 lenses (not all Nikon) with what seems to be a good target I have never had a front or back focus issue. What you accept is up to you - but if the Sigma needs 17 with a good AF target I would not hesitate to do what you did - and reject it. I might go to 1 or 2 with a second hand lens - but no more.
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Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.
#2. "RE: Whats the most you would fine tune focus a lens before you decide to return it?" | In response to Reply # 1lewys Registered since 07th Jun 2011Tue 28-Jun-11 07:21 PM | edited Tue 28-Jun-11 07:26 PM by lewys
I just tested my 50mm 1.8 and that is perfect and so is my tamron 90mm macro.
I also tested the sigma again and at 70 mm it seems i have to apply fine focus tuning to +18 but at 200mm it only needs +7.
As it was getting darker i tried taking photos of a fence that was about 7ft away(focusing on just one bar) and the focus seemed to be a lot better when the fine tune focus was set to 0. When i was testing it on things earlier when i had to adjust the fine tune focus, the subject was only about 4 foot away.
I will have to try the fence thing tomorrow though and look at the results because it could have just looked better because it was dark
By the way the closest focusing distance for this lens is 3.28ft.
#3. "RE: Whats the most you would fine tune focus a lens before you decide to return it?" | In response to Reply # 2JohnE Nikon Registered since 15th Jun 2010Wed 29-Jun-11 01:15 PM | edited Wed 29-Jun-11 01:17 PM by JohnE Nikon
Fine tuning lenses should not be taken lightly as it easy to fine-tune incorrectly.
Len and I have debated much on these forums regarding fine-tuning.
I have a used lens which needs -18 fine tuning. I bought this lens used and with fine tuning I am perfectly happy with the results.
It is crucial to have a good focus target that is well lit.
I have experimented with multiple free online focus tests and finally used Lens allign pro to ensure my results were reliable.
After much testing I have found
A zoom lens will likely not need the same fine-tuning at it's extremes. If you fine tune in the mid range of zoom see if you are happy enough with results at extremes.
Some lenses change drastically with a 2 or 3 units of fine tuning while other lenses have a similar change with 10 or more units of fine tuning. It is like the manual focus dial where slight changes on some lenses effect focus more or less depending on lens.
Fine tuning may be different when focusing on a near subject as opposed to a far subject.
Fine tuning may give different results with a well lit subject as opposed to a subject in suboptimal light.
It gets confusing and I would try a few different methods of fine tuning and try out equipment on real subjects and determine if you are satisfied. I am confident with my results with my lens that needs -18 fine tuning and choose not to return it.
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