Proper focus?


Jetsam1

Link Posted 26/05/2013 - 10:44
Hi,

This is a snap shot I took this morning and I have managed to convince myself today and yesterday that my focusing is somewhat out. Chances are it's just me being stupid and seeing things when there is nothing to see. I am not familiar with what back or front focusing looks like.
I picked this as it is a fairly busy view. K5 with DA* 16-50 at f11 ISO 100 and 1/100 shutter speed.



K5, K200 and several film Pentax cameras!

johnriley

Link Posted 26/05/2013 - 10:52
What did you focus on? f/11 should render most things sharp anyway as DOF will be quite large at the distances involved. Lens quality and shutter speed (for camera shake considerations) will have an influence.

This isn't the subject, nor is it the aperture, to test focusing accuracy.
Best regards, John

wvbarnes

Link Posted 26/05/2013 - 10:58
Hi Scott, John is right, what were you wanting to focus on as the subject of your photos.

I personally use centre focusing most of the time and keep a lock on if re-framing off centre. This example makes any further comment difficult.

Generally stopped down and or wide angle give the greatest depth of field. Most of the comments on forums about errors are about very fast prime lenses at maximum aperture or long telephoto.

Jetsam1

Link Posted 26/05/2013 - 11:04
Ok, I think it defininatively says I really don't know what I'm doing!

This is at f2.8 same lens shutter speed of 1000 as was using Av so should be no impact from shake.. Focusing on the front petal. Is this more the sort of thing to use?



K5, K200 and several film Pentax cameras!

johnriley

Link Posted 26/05/2013 - 11:17
If you focused on the front petal, then that's the sharpest point, so you don't seem to have a problem.

It is possible to take a more technical approach, and there are several threads on the forum on the subject. A scale at 45 degrees is often used.
Best regards, John

CIBarker

Link Posted 26/05/2013 - 11:20
100% agree with John, and I really like this image, some great colour captured, looks nothing wrong to me.
Chris

wvbarnes

Link Posted 26/05/2013 - 11:29
That's a nice photo, stopping down a bit would have allowed more of the flower to be in focus. No need for such a high shutter speed though, it isn't going anywhere.

I think a lot of people moving from extreme wide angle in phones or compact cameras are taken aback by the control (and thought needed) when they move to the longer focal lengths DSLR's use. A good explanation is in your cameras handbook.

petrochemist

Link Posted 26/05/2013 - 15:32
wvbarnes wrote:
That's a nice photo, stopping down a bit would have allowed more of the flower to be in focus. No need for such a high shutter speed though, it isn't going anywhere.

Looks to me like it has quite a long stalk, so with only a breath of wind it will move significantly. As Jetsam1 was particularly concerned that he was not nailing focus a wide aperture & fast speed is the best way to tell.
Possibly more useful if the object was to get the DOF improved would be to focus on one of the petals further back near the middle of the flower, so as to use DOF both before & behind the point of focus, though a stop or two would probably been worthwhile too.
For Jetsam1's purpose the shot works well, focus looks fine to me, though a 100% crop might show a minor discrepancy.
Mike
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
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Jetsam1

Link Posted 26/05/2013 - 15:46
I feel better now, just not used to the DA* after the kit lens and film MF for a year! I think the harsh sunlight was fooling the meter a bit and softening everything up. Never had an issue with focus before..... Just paranoid I think.....
K5, K200 and several film Pentax cameras!
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