my EF 100mm f2 has problem focusing on low contrast objects and eyes

[theorium]

I have an EF100mm f2 that I use on my EOS 6D (also taste on EOS500D). there are a lot of instances when it goes on an endless hunt for focus and never stops till I move it. it starts going in and out. it mostly happens on low contrast objects but it happens on high-contrast things too, which the most annoying one is focusing on eyes.
I want to know if it's a common issue with this oldy lens or if I should send it for repair.

[jrhoffman75]

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@theorium wrote:

I have an EF100mm f2 that I use on my EOS 6D (also taste on EOS500D). there are a lot of instances when it goes on an endless hunt for focus and never stops till I move it. it starts going in and out. it mostly happens on low contrast objects but it happens on high-contrast things too, which the most annoying one is focusing on eyes.
I want to know if it's a common issue with this oldy lens or if I should send it for repair.

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The AF system needs contrast to focus. What focusing mode are you using? Do other lenses show a similar behavior when trying to photograph the same subjects?

[theorium]

I tried with my Tamron 24-70 and the infamous 50mm f/1.8 II and they had difficulty pinpointing the focus but were more successful and didn't on loop

[shadowsports]

Greetings,

In addition to John's suggestions, please ensure you are not attempting to focus on a subject closer than the lenses MFD (12 inches).  

EF 100 f2.8 Manual

[theorium]

thanks, but no that's not the problem

[ebiggs1]

Sounds like you just need more light.

[theorium]

kinda yes, so is the behaviour of the lens normal you say?

[jrhoffman75]

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@ebiggs1 wrote:

Sounds like you just need more light.

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Specs for 6D show AF down to EV -3. That's basically full moon at night.

[Tronhard]

Hi and welcome:
It would be helpful to know precisely what settings you using for focus:
Focus type - One shot, AI, or Servo
selectable focus points = 61, Only cross-type, 15 Points, 9 points
Has anything else changed?  A different setting of any kind, a front filter etc.?

Thank you.

[theorium]

one shot , 9 points (using the center) no filters,
based on the questions everyone is asking, I am assuming the lens has a problem.