So I bought a 200mm f1.8 and...

[TexPhoto]

I bought a 200mm f1.8 on eBay. Described as working perfectly and cosmetically near perfect. Shipped over from Japan. It looks GREAT. Cosmetically its a 9.9 out of ten.

And it works, but it autofocuses in a strange manner. It finds AF, but then seems to dance around it, and it makes noise (sound). I'm using Servo mode like I always do. The photos seems sharp as a tac. I've tried it on an R3, an R7, and an RP. I've tried 3 different canon RF to EF adapters. Results are all the same.

My question is this normal? The lens was released in 1988. It's 35 year old tech.

 

[koenkooi]

Older and non-macro EF lenses have very coarse steps in the encoders for the focus motor, so I suspect it can’t find the exact distance the camera wants due to the lack of precision.

 

[shadowsports]

I don't really follow old glass, but lenses manufactured before 2009 don't support dual pixel AF. Buying used lenses can be good or bad. Not sure about the noise thing? That lens is going to struggle keeping up with the back and forth communication between a R series body and lens. MFD is 8.2ft. It will probably do its best with subjects at 20+ft.

 

[davidespinosa]

Why don’t old lenses support DPAF ?
(just curious, not disagreeing)

 

[shadowsports]

Hi David,
DPAF was introduced on the 70D. My understanding is that the communication protocols and focus motors (on old lenses) are not able to respond quickly enough to process the signals from the pixels on the image sensor, Lenses still work, but some will work more slowly or fail to follow or track a subject accurately. I'll see if I can find something more definitive from Canon.

 

[davidespinosa]

I see. You’re saying DPAF works, but the lens isn’t fast or precise enough to take advantage of it. Right ?

 

[shadowsports]

Yes. EF protocols have not remained stagnant since release. This is why some lenses work better when adapter to RF also. I really do need to find the docs I read to back up what I'm saying.

 

[Sporgon]

I don't really follow old glass, but lenses manufactured before 2009 don't support dual pixel AF. Buying used lenses can be good or bad. Not sure about the noise thing? That lens is going to struggle keeping up with the back and forth communication between a R series body and lens. MFD is 8.2ft. It will probably do its best with subjects at 20+ft.

Your post got me thinking….
I put my 1996 era EF 200/2.8 II on my RP, which as you know only used DPAF to focus. In both one shot and servo it was fine; fast and accurate. However, I noticed that in Servo the ultrasonic motor would keep operating, not exactly hunting, or at least not visibly, the degree to which depended on the subject, and often wouldn’t stop, but despite this the picture was in sharp focus. When I tried a 2012 lens it would sometimes do the same, but to much lesser a degree, usually stopping once it had focus and subject wasn’t moving.
So yes, I can see that these earlier lenses don’t behave entirely as they should when using Servo mode on mirrorless.

 

[TexPhoto]

Thanks for the responses. I had a chance to use the lens in a photoshoot over the weekend. Engagement photos for my nephew. The lens worked great and the photos are stunning. I shot with the EF 70-200 f2.8 III as well and had a chance to compare them. The 70-200 was a little faster, but the 200mm f1.8 held its own and certainly delivers a photo with a unique look.