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Pentax K mount to EOS help
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PostPosted: Wed Jan 16, 2019 2:16 pm    Post subject: Pentax K mount to EOS help Reply with quote

Just bought myself a Pentax SMC 1.7/50. I'm using it on a Canon 400D with a AF confirm adaptor. The problem I'm having is that the focus is out when the AF confirm beeps. It's usually focused behind the subject. I've tested a Vivitar zoom with the same set up and the AF is fine. I wondering if it's due to some tiny barely noticeable fungus in the Pentax lens. It's so small you can only see it if you shine a torch threw the lens. Could something so small throw the AF confirm out or is it something more terminal with the lens? Once I adjust the focus by eye it takes perfect sharp pictures.

Cheers guys.


PostPosted: Wed Jan 16, 2019 8:32 pm    Post subject: Reply with quote

On my pentax I have the option of fine tuning the focus accuracy (correcting for slight front or back focusing) - can you do that with your canon?


PostPosted: Wed Jan 16, 2019 9:54 pm    Post subject: Reply with quote

marcusBMG wrote:
On my pentax I have the option of fine tuning the focus accuracy (correcting for slight front or back focusing) - can you do that with your canon?


Not that i know of. It would be a handy feature.


PostPosted: Wed Jan 16, 2019 10:11 pm    Post subject: Reply with quote

The 400d cannot micro-adjust autofocus. It has no live view for accurate manual focussing. It has a dark pentamirror so using the viewfinder isn't ideal either. It is an almost 11 year old camera. Better invest in a newer camera. If you want to shoot legacy glass mirrorless is the way to go.


PostPosted: Wed Jan 16, 2019 10:22 pm    Post subject: Reply with quote

D1N0 wrote:
... Better invest in a newer camera. If you want to shoot legacy glass mirrorless is the way to go.


Indeed, a Pentax might be an option in this case Wink


PostPosted: Wed Jan 16, 2019 11:51 pm    Post subject: Reply with quote

You can try turning focus ring from infinity until AF beep, or, from too close until AF beep. One way or the other may give better consistent results.

You can focus by viewfinder, using the AF points to determine focus, or by eye. Note unless a fast focus screen is installed accurate focus by eye is impossible at apertures smaller than about f/2.8.