AF adjustment of old Sigma lens?

I recently purchased a used Sigma 400mm f/5.6 APO Tele Macro, a screw-drive lens dating from I don't know when. The lens is quite good, but it does front-focus a lot. An AFFT setting of +20 (the maximum value available on my D810) results in acceptable sharpness, but I can still get slightly sharper images by focusing manually. I estimate +25 AFFT would be perfect.

What I want to ask the forum is: Does anybody have experience with sending out-of-production lenses to Sigma for adjustment? Will they service a lens this old? If so, how much would they charge?

Alternatively, can anyone suggest a home remedy for a lens that front-focuses just a bit more than the camera can compensate for? Tweaking focus manually after AF is not convenient on this lens, and, with its short focus throw, it's not easy either.

Aside from getting it serviced, the only thing I ever found that worked was shooting in live view and using the magnifier to check focus.

Ah. Yes. I forgot to mention that this lens refuses to focus in Live View. It performs the initial, gross movement, but then skips the finer oscillations that are supposed to home in on proper focus. Very strange; I've never had a lens do this before. It hasn't bothered me because I don't use Live View, but it's true that this failure closes off one way of addressing the front-focusing issue.

Maybe the problem is actually that there's a bit of slack in the mechanical AF gear train? (Does it definitely always front-focus?) Sigma are trying hard to make up for their historical reputation for shoddy lenses; I imagine it couldn't hurt to ask them.

Andrew, this lens's AF mechanism is actually very precise and consistent. It always front-focuses just a little too much for the camera to compensate for. I've owned Nikon lenses that had far more shot-to-shot variance.

Anyway, i've now sent an e-mail to Sigma, which could be answered as early as Monday. I'll report back on how they reply.

Ah. Yes. I forgot to mention that this lens refuses to focus in Live View. It performs the initial, gross movement, but then skips the finer oscillations that are supposed to home in on proper focus. Very strange; I've never had a lens do this before. It hasn't bothered me because I don't use Live View, but it's true that this failure closes off one way of addressing the front-focusing issue.

You might be stuck with live view and manual focus...

You might be stuck with live view and manual focus...

If you can believe it, it's easier to focus this lens through the viewfinder. In Live View, with enough magnification for precise focusing, the view is very shaky. Partly this is because of my cheap tripod, but also the lens's tripod collar isn't sturdy.

If you can believe it, it's easier to focus this lens through the viewfinder. In Live View, with enough magnification for precise focusing, the view is very shaky. Partly this is because of my cheap tripod, but also the lens's tripod collar isn't sturdy.

In case it helps, try wedging a film cannister (or asthma inhaler) between the lens and tripod foot. I believe that's the budget alternative to a long lens support. (Or I have one of these, but it's quite heavy.)

In case it helps, try wedging a film cannister (or asthma inhaler) between the lens and tripod foot. I believe that's the budget alternative to a long lens support. (Or I have one of these, but it's quite heavy.)

Nice. I knew Manfrotto made a long-lens support, but this one looks easier to use and is cheaper.

 

What I want to ask the forum is: Does anybody have experience with sending out-of-production lenses to Sigma for adjustment? Will they service a lens this old? If so, how much would they charge?

Just give them a ring..

My experience with Sigma services is that they are verry friendly and always willing to help out, but tha is the Sigma service here in the Netherlands, i guess it will be similar in the US ...

I've seen a list somewhere of the lenses they can re-chip. I'll see if I can dredge it up.

Is re-chipping how they fix AF issues?

Just give them a ring..

 

My experience with Sigma services is that they are verry friendly and always willing to help out, but tha is the Sigma service here in the Netherlands, i guess it will be similar in the US ...

Thanks, i have emailed, and i'll call them if no response in a few days.

I'll bet Dutch customer support reps are nice because the customers are reasonable. People may be less reasonable here in America.

Is re-chipping how they fix AF issues?

It's how they address the non-working AF in LV.

Welp, Sigma responded:

So much for that. I wonder if an independent shop might service the lens.

Oh dear. Sorry to hear that - thanks for letting us know. Fingers crossed for a third party, but it may just be that it'll cost more than the replacement cost to fix.

Quite likely!

How accurate is the <> rangefinder?

Do you have any other bodies to see if it's the cumulative 'combo' of your D810 and Sigma 400mm that results in the need for the unobtainable +25?

Do any of your other Nikon lenses have much AF fine tune needed?

Hypothetically, your D810 might inherently need +15 and the Sigma needs an additional +10. Can't be one.

But, if you've got, say, a D700 that inherently needs -5, a final cumulative of +5 is easy.

How accurate is the <> rangefinder?

 

Do you have any other bodies to see if it's the cumulative 'combo' of your D810 and Sigma 400mm that results in the need for the unobtainable +25?

 

Do any of your other Nikon lenses have much AF fine tune needed?

 

Hypothetically, your D810 might inherently need +15 and the Sigma needs an additional +10. Can't be one.

 

But, if you've got, say, a D700 that inherently needs -5, a final cumulative of +5 is easy.

This is an excellent point. My other lenses require anywhere from -5 to +12 AFFT, with some needing none. However, the ones that need positive adjustment outnumber the ones that need negative.

This does implicate the body, doesn't it? (I have no other.) If I could have the D810 adjusted so that a lens that currently needs +5 AFFT would need none, then the 400mm lens would become perfect at +20.

How much does Nikon charge for adjusting the AF on a body?

How much does Nikon charge for adjusting the AF on a body?

Um, never mind. Nikon's online quote for AF adjustment is $282.95. That's significantly more than what I paid for the 400mm lens.

Someone told me, and no it wasn't the bloke down the pub, that it's just a little screw 'somewhere' in the mirrorbox' that adjusts the length of the optical flight path to the AF module, so changing the overall + or - calibration.

DIY?

Hopefully someone else can chime in here...:)

There's 3!

This is quite interesting. Comments below the vid seem to indicate this mechanism is common to a lot of different Nikon DSLRs.

Makes sense. Not going near it with my bodies.

I concur.