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08-19-2009, 06:50 AM   #1
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Help required - Sigma 28-70 f2.8

Hi Guys

got a bit of a wierd one here, i have a sigma 28-70 f2.8 DF ex that has suddenly started playing up!

the aperture keeps on displaying as F-- when the lens is supported from underneath, not every time but its easy to recreate by adding a bit of pressure. I can also get it to do it if i move the aperture ring slightly (it has a small amount of slack in it at A)

i have cleaned the contacts (camera and lens) with some electrical contact cleaner and still no joy..

has anyone else had this? and could they shed some light on what would cause it?

Thanks in advance


08-19-2009, 07:04 AM   #2
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I've not had this issue but I suspect something is loose. It might be that the contacts are just barely connecting (weak or broken spring) and any pressure upwards is causing it to loose communication with the body. The loose A setting would simply be that by turning it enough, you are no longer in the A setting.

Has the camera and lens attached been knocked or dropped? Is the mount between the lens and body loose in any way? Do any of the contacts appear depressed on either side of the mount? Any issues with other lenses? Is it still under warranty? Do you have a friend that has a similar body you could test it on or a store that has any K mount body?

I would suggest it go to Sigma for a checkup if you can send it in.
08-20-2009, 05:11 PM   #3
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Original Poster
Hi Peter and thanks for that..

all contacts are in good order and depress and return nicely when pushed.. i have cleaned themn sufficiantly i beleive (lens was in as new condition when bought) and camera was purchased in march!

i have been around with a precision screwdriver and tightenened things up although nothing was loose as such.. just a small amount of turning available on a couple of screws.

after depressing the contacts on both the camera and the lens the problem seems to of gone away so maybe something wasnt sitting right somewhere..

it did take a bit of a knock but nothing too bad.. the bag was sat under a table when i got cramp in the back of my leg and i caught the bag just as i kicked and stood up! i dont think i hit it hard tho .. just glanced..

we do have a sigma service centre close by so i can drop it into them if the problem surfaces.. i was on about getting it serviced anyway.



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