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Focusing issues on Pentax cameras

pschlute
Posted 26/07/2017 - 13:42 Link
Ok so live View is not as accurate as the focus-rail they used in the article. But in their words "The results here [Live view] are clearly much better than those achieved by either the camera's own AF system or by manually focusing using the optical viewfinder."

If i want to absolutely nail focus to the best of my ability on a subject i will use a tripod and LV viewed at 100%. with the lens wide open if needed. Tell me a better method?

Sorry if my post was confusing about Live view. i did not mean to imply that the LV Contrast Detect system has anything to do with autofocus adjustment.
Algernon
Posted 26/07/2017 - 13:47 Link
LV doesn't look at the camera settings. It just opens/closes the aperture in 2 stop steps to get the proper picture on the LV screen at least on the K-5. I think other marques will allow the aperture to be selected. (Maybe the K-1 does? )

Still not much use unless you have some sort of micro adjustment on the lens focus to get within +/- 7mm. A focus rack is easier, but you still have the problem that it will probably only be correct at that one distance.

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Edited by Algernon: 26/07/2017 - 13:55
johnriley
Posted 26/07/2017 - 15:11 Link
There is also the problem of focus shift. Lenses can change the point of focus when stopped down. They more often than not also change the point of focus (very dramatically) when zoomed.

Fortunately, the amount of precision we can achieve is sufficient to ensure top quality results.
Best regards, John
JAK
Posted 26/07/2017 - 16:31 Link
pschlute wrote:
If i want to absolutely nail focus to the best of my ability on a subject i will use a tripod and LV viewed at 100%. with the lens wide open if needed. Tell me a better method?

From Sabas's test of liveview with electronic shutter, it might lead to a sharper image for more reasons than just focussing (seemed shutter vibration could have been an issue.)
John K
Edited by JAK: 26/07/2017 - 16:32
pschlute
Posted 26/07/2017 - 17:02 Link
Yes John , I experienced the shutter shock myself when using speeds in the range 1/30-1/200. But I am talking simply about focussing. When using LV zoomed 100% the big screen on the K1 makes manual focussing so much easier than using the viewfinder. The image is much much bigger. No use at all of course when off the tripod or with a moving subject.
JAK
Posted 26/07/2017 - 17:11 Link
pschlute wrote:
Yes John , I experienced the shutter shock myself when using speeds in the range 1/30-1/200. But I am talking simply about focussing. When using LV zoomed 100% the big screen on the K1 makes manual focussing so much easier than using the viewfinder. The image is much much bigger. No use at all of course when off the tripod or with a moving subject.

I'll have to have a play trying that (be interesting with that 300 2.8!)
John K
Edited by JAK: 26/07/2017 - 17:12
pschlute
Posted 26/07/2017 - 18:43 Link
JAK wrote:

I'll have to have a play trying that (be interesting with that 300 2.8!)

That is exactly the FL (+ longer) where you will notice it
SteveLedger
Posted 26/07/2017 - 21:47 Link
Yecora99 wrote:

I also own an Olympus OM-D EM-5 DSLR and the focus point on that is spot on.

A minor point, but I can't let it go uncorrected.
A mirrorless camera by definition is not a DSLR.
They are MILC cameras, though Panasonic coined 'DSLM' which I like better
Edited by SteveLedger: 26/07/2017 - 21:48
pschlute
Posted 26/07/2017 - 22:01 Link
SteveLedger wrote:
Yecora99 wrote:

I also own an Olympus OM-D EM-5 DSLR and the focus point on that is spot on.

A minor point, but I can't let it go uncorrected.
A mirrorless camera by definition is not a DSLR.
They are MILC cameras, though Panasonic coined 'DSLM' which I like better

....and being a mirrorless camera presumably uses Contrast detection AF which has no need to be adjusted, like LV on a DSLR
JAK
Posted 26/07/2017 - 23:14 Link
pschlute wrote:
SteveLedger wrote:
Quote:

I also own an Olympus OM-D EM-5 DSLR and the focus point on that is spot on.

A minor point, but I can't let it go uncorrected.
A mirrorless camera by definition is not a DSLR.
They are MILC cameras, though Panasonic coined 'DSLM' which I like better

....and being a mirrorless camera presumably uses Contrast detection AF which has no need to be adjusted, like LV on a DSLR

We've just gone full circle. See my reply immediately after the OP's original post!

As to DSLR, that's the abbreviation for Digital Single Lens Reflex which describes the fact that a mirror or prism transfers the image to a viewfinder. The Oly doesn't have a viewfinder and mirror or prism hence the DSLR description is not appropriate. I don't believe they make DSLR's any more.
John K
Edited by JAK: 26/07/2017 - 23:24
richandfleur
Posted 27/07/2017 - 06:23 Link
pschlute wrote:


....and being a mirrorless camera presumably uses Contrast detection AF which has no need to be adjusted, like LV on a DSLR

Depends on the mirrorless camera.

Like the Pentax K-70, some cameras have phase detect autofocus sensors on the camera image sensor itself. These span right across the sensor, so aren't limited to the centre area like a typical DSLR.
Edited by richandfleur: 27/07/2017 - 06:23

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