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Pentax SR wrong focal length input

bjolester
Posted 13/10/2017 - 14:34 Link
Some days ago I took some shots with my Pentax K-5iis and a manual focus 30mm lens. When looking at the images today, I realised I had forgotten to input the correct focal length, the focal length input in the SR system was 50mm.

The images look OK, but I am unsure what negative impact the wrong SR focal length could have had on these images? Will the images be less sharp than they would have been with the correct SR value?

I am grateful for any advice on this matter!
Bjørn

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pschlute
Posted 13/10/2017 - 14:51 Link
If you input a FL more than the one you are using you can get blur caused by the SR mechanism over-compensating for camera shake. You would notice this if you input 300mm and used a 100mm lens. In your case I doubt you would see much difference.

Other factors that will influence this of course are the amount of camera shake you exhibit....not much I would suspect with a 30mm lens, and the shutter speed you are using (the faster the shutter the less there is to compensate for.

anyway, you took the photographs and you say the pictures are OK...so no harm done
Edited by pschlute: 13/10/2017 - 14:52
bjolester
Posted 13/10/2017 - 15:08 Link
Thank you Peter! The most interesting shots were taken with 1/125 and 1/160 shutter speeds, and the images look OK on the camera lcd. I have just returned from a holiday travel, and have not had the time to study the images on a proper monitor yet.

I have seen how the SR works when using telelenses on a tripod, and forgetting to turn the SR off. Then image blur and loss of sharpness can be easily observed. However, with my mistake described above, the possible detrimental effect of wrong SR FL input is harder to spot, hence my question.
Bjørn

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Flickr
GlynM
Posted 13/10/2017 - 19:25 Link
bjolester wrote:
I have seen how the SR works when using telelenses on a tripod, and forgetting to turn the SR off.

If you turn on the 2s self timer, which I often do when using a tripod, then SR is automatically disabled. On moving away from the self-timer setting SR returns to its previous setting. I think SR is also disabled for some of the other modes like remote control and mirror-up. You can see this happening by checking the current SR status in the info screen.

Glyn
Edited by GlynM: 13/10/2017 - 19:29
davidtrout
Posted 13/10/2017 - 19:31 Link
GlynM wrote:
bjolester wrote:
I have seen how the SR works when using telelenses on a tripod, and forgetting to turn the SR off.

If you turn on the 2s self timer, which I often do when using a tripod then, SR is automatically disabled. On moving away from the self-timer setting SR returns to its previous setting. I think SR is also disabled for some of the other modes like remote control and mirror-up.

Glyn

On the rare occasions I use a tripod I set the timer delay for 12sec and that also disables the SR. The longer delay gives any possible vibration from setting it up to settle down. As for matching lens focal length to the SR surely the camera does that automatically?
David
David
Edited by davidtrout: 13/10/2017 - 19:48
screwdriver222
Posted 13/10/2017 - 21:27 Link
Quote:
As for matching lens focal length to the SR surely the camera does that automatically?

Except when a manual lens, which has no contacts, is used

Jeff
bjolester
Posted 14/10/2017 - 00:38 Link
Thanks GlynM, David and Jeff for commenting!
Bjørn

PPG
Flickr

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