GM 300/2.8 AF problems

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Andrew Nik

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I shot for two days over the weekend and here's what I noticed. Sometimes the AF stops working for no reason. I press the AF-ON button and the AF icon blinks green, but does not confirm. Focus limiter set to Full, distance to object more than 5 meters. AF-C mode (Spot L).

It helps to just wait, or switch between AF-MF. I usually observed this at the beginning of a walk. Then within an hour and a half everything was perfect, I shot about 4000 frames.

Is this a lens malfunction, or has anyone else noticed this? Does it make sense to update the camera firmware to 2.0? (I haven't updated yet)

No problem with IQ, it is excellent.
 
Solution
IT WAS F#%$#ING "functional ring" with f**ing "power focus" function!!!
I accidentally touched this ring and didn't notice it because I was wearing gloves while shooting. And it interferes with the normal operation of AF.
I'd start with cleaning the contacts on the lens and camera with light alcohol like nail varnish remover on a cotton bud.
 
I shot for two days over the weekend and here's what I noticed. Sometimes the AF stops working for no reason. I press the AF-ON button and the AF icon blinks green, but does not confirm. Focus limiter set to Full, distance to object more than 5 meters. AF-C mode (Spot L).

It helps to just wait, or switch between AF-MF. I usually observed this at the beginning of a walk. Then within an hour and a half everything was perfect, I shot about 4000 frames.

Is this a lens malfunction, or has anyone else noticed this? Does it make sense to update the camera firmware to 2.0? (I haven't updated yet)

No problem with IQ, it is excellent.
we might need more info camera body tacking or not? background could be a lot of reasons for what you are seeing
 
Not yet, I'll try today. But with 200-600 before that everything worked fine.
Does it still work ok with the 200-600? Try other lenses, process of elimination. If everything else works, it's the lens.
 
This was repeated many times over three days against any background and at any distance to the object. Maybe it's something to do with the AF settings? Just in case, I switched the Shutter priority setting from Release to Balanced Emphasis, since then not a single failure, but it was already the middle of yesterday’s walk. Whether it helped or not can only be said at the next shooting. I thought that it might also have to do with the Full time DMF setting, but this does not affect it. Unless turning on DMF allows you to move the focus in case of a failure, and this also usually helps.
 
This was repeated many times over three days against any background and at any distance to the object. Maybe it's something to do with the AF settings? Just in case, I switched the Shutter priority setting from Release to Balanced Emphasis, since then not a single failure, but it was already the middle of yesterday’s walk. Whether it helped or not can only be said at the next shooting. I thought that it might also have to do with the Full time DMF setting, but this does not affect it. Unless turning on DMF allows you to move the focus in case of a failure, and this also usually helps.
Well release is useless in my opinion, release does not mean focus!
 
I'd start with cleaning the contacts on the lens and camera with light alcohol like nail varnish remover on a cotton bud.

Nail varnish remover, as I understand it, is not light. It's active ingredient is acetone, which is a powerful solvent.

Very dangerous to any plastic.
 
IT WAS F#%$#ING "functional ring" with f**ing "power focus" function!!!
I accidentally touched this ring and didn't notice it because I was wearing gloves while shooting. And it interferes with the normal operation of AF.
 
Solution
IT WAS F#%$#ING "functional ring" with f**ing "power focus" function!!!
I accidentally touched this ring and didn't notice it because I was wearing gloves while shooting. And it interferes with the normal operation of AF.
Glad you figured it out, that must have been so frustrating!
 
I love my Samyang 135. But every so often, the aperture refuses to change, or changes mysteriously.

Yes, I have it sussed now, but it always takes me a few moments of worry before I remember that the lens mode switch changes the ring focus <--> aperture.
 
IT WAS F#%$#ING "functional ring" with f**ing "power focus" function!!!
I accidentally touched this ring and didn't notice it because I was wearing gloves while shooting. And it interferes with the normal operation of AF.

That would operate like “Fulltime DMF” + moving the focus ring! That would be such a pain to work out. Congratulations on solving that one.
 

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