Sigma 60-600 not focusing with Polarizer....Why?
Aug 15, 2019 22:45:27 #
User ID wrote:
A camera that can AF a 5.6 lens will AF it br ev... (show quote)
Polarizers do change your f-stop - oniy it is just not communicated to the camera's "brain" - like an extender is through the lens' mount pins....so it will still TRY to AF ....
Aug 15, 2019 22:50:08 #
Interesting article on autofocus here. https://photographylife.com/dslr-autofocus-modes-explained
It doesnt address polarizers but does discuss impact of low light in phase/contrast detection. Suggests using single center af point or live view, among other ideas.
It doesnt address polarizers but does discuss impact of low light in phase/contrast detection. Suggests using single center af point or live view, among other ideas.
Aug 16, 2019 00:28:31 #
captxmas
Loc: San Francisco Bay Area
To clarify..... I am using a Nikon D-500. I have tried boosting ISO to experiment and change to different f-stops. The whole range for sample shots. Without the CPL, all shots are tack sharp (or close to it). With the filter ALL shot AF does occur but does not get to the Sharp point. Imagine stopping just short of focus and just a little blurry. Its as though the lens is doing what it is supposed to do but falling short. Maybe the filter is acting like another lens element?
Shots are being taken outside in full sun with targets at different ranges and colors around my yard 6' - 40' distance.
Hope this helps identify what might be going on.
Shots are being taken outside in full sun with targets at different ranges and colors around my yard 6' - 40' distance.
Hope this helps identify what might be going on.
Aug 16, 2019 06:04:37 #
I have known this to happen with CANON lenses, not necessarily with polarising filters either. My neighbour sent an e-bay purchase lens to CANON. They returned it (with the filter removed) and cleaned it up and it's worked perfectly ever since.
Aug 16, 2019 08:18:31 #
Dark filters, specially if using matrix metering tend to fool the AF and the meter. May I suggest that you AF and take an exposure WITHOUT the filter and then keep the camera in manual focus and fit the filter on the lens while adding two full stops to compensate for the filter factor at full polarization.
Aug 16, 2019 08:23:55 #
camerapapi wrote:
Dark filters, specially if using matrix metering tend to fool the AF and the meter. May I suggest that you AF and take an exposure WITHOUT the filter and then keep the camera in manual focus and fit the filter on the lens while adding two full stops to compensate for the filter factor at full polarization.
Aug 16, 2019 08:59:12 #
imagemeister wrote:
You loose 2 stops of light with the polarizer - just like with a 2X extender ! So the AF WILL be affected !
The other "problem" using any filter with long focal length lenses is that focusing issues are exacerbated .....and each filter and lens has a unique/different reaction regarding this. I cannot explain all the physics involved with this - just know that it happens ! and, is why I use any filter as a last resort....
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The other "problem" using any filter with long focal length lenses is that focusing issues are exacerbated .....and each filter and lens has a unique/different reaction regarding this. I cannot explain all the physics involved with this - just know that it happens ! and, is why I use any filter as a last resort....
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Just FYI the best new circular polarizers have much better transmission of light and you only lose one stop nowadays. Some circular polarizers may cause an issue with some camera's autofocus abilities, that is a known fact,sadly.
Aug 16, 2019 09:35:41 #
captxmas wrote:
Greetings all, I have been a long time user of pol... (show quote)
Please make sure that the filter is legit, and if you're in auto focus mode, you may need what is know as CPL polarization filter. Read what I've said here: https://www.uglyhedgehog.com/t-603730-2.html#10390290
The new Gobe Polarization filter technically listed as an official "CPL" will arrive later today.
Edit: here's a quick tip to check the filter, Remove the filter from your lens, hold it in front of the computer screen then slowly rotate the outer ring, Check to see if the filter gradually goes from light to dark and watch the window's icons on the screen they should go nearly or complete black, if they do not your filter could be counterfeit, But we would need to check other areas of the filter and packaging to verify.
Aug 16, 2019 09:45:38 #
I had a similar problem on a Nikon 80-400. When I took the filter off it was fine. The camera wouldn't focus because of the low amount of light hitting the sensor.
Aug 16, 2019 09:46:16 #
amfoto1 wrote:
You didn't mention what camera you have, but some ... (show quote)
Yes the filter makes it unable to focus, but the aperture is still in the range where it attempts to focus. The camera is just not getting enough light to succeed. The OP said:
captxmas wrote:
I have tried to use two different 105mm polarizers and the lens will not deliver a sharp image until it is removed.
The images, while not "sharp" would seem to be view-able if not usable. So it seems the AF is trying to work. It would have been nice to see the image and know the settings used.
Aug 16, 2019 09:56:50 #
Steve Perry had a nice video on focus problems. One hint I wouldn't have thought of, clean the af sensors!
https://backcountrygallery.com/solving-autofocus-problems-8-common-af-problems-and-solutions/
https://backcountrygallery.com/solving-autofocus-problems-8-common-af-problems-and-solutions/
Aug 16, 2019 10:19:36 #
bleirer wrote:
Steve Perry had a nice video on focus problems. One hint I wouldn't have thought of, clean the af sensors!
https://backcountrygallery.com/solving-autofocus-problems-8-common-af-problems-and-solutions/
https://backcountrygallery.com/solving-autofocus-problems-8-common-af-problems-and-solutions/
Cleaning the focus sensor? I never thought about that! I just do the image sensor.
Thanks
Aug 16, 2019 10:31:39 #
With some large lenses ,it would appear that one has to pre-meter the light before the application of a filter because of the loss of f-stop in some instances and manually add or subtract exposure accordingly. This seems to be the case for 2nd party lenses and tele-converters and especially N.D. filters on these lenses.
Auto focus would also be affected and the camera may never achieve it as a result. I wish I knew more about this and hope others will chime-in with the correct answers. Trial & Error are what I wind-up doing usually and that's not the smartest way but it eventually yields a result. At least with digital , we get instant results and don't to wait for film processing any more....like we used to. Those were the days !
Good luck to you.
Auto focus would also be affected and the camera may never achieve it as a result. I wish I knew more about this and hope others will chime-in with the correct answers. Trial & Error are what I wind-up doing usually and that's not the smartest way but it eventually yields a result. At least with digital , we get instant results and don't to wait for film processing any more....like we used to. Those were the days !
Good luck to you.
Aug 16, 2019 11:10:02 #
RRS
Loc: Not sure
dsmeltz wrote:
Cleaning the focus sensor? I never thought about that! I just do the image sensor.
Thanks
Thanks
I could be wrong but I don't think it's an easy thing to do because of it's location.
Aug 16, 2019 11:13:27 #
RRS wrote:
I could be wrong but I don't think it's an easy thing to do because of it's location.
The Steve Perry link posted earlier by bleirer shows how.
https://backcountrygallery.com/solving-autofocus-problems-8-common-af-problems-and-solutions/
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