Kr - AF Fine Adjustment


surfseen

Link Posted 28/07/2011 - 12:32
Always looking for the sharpest possible photo. Under the Custom settings No 21. Does the fine adjustment only affect the current lens, or any lens attached to the camera.

Taking pictures of a light bulb inside, with the built in flash using the 55-300 pentax lens. The bulb comes out sharp at the 300mm, but at 55mm it is not as sharp. Any ideas of what the cause would be.
Andrew
KR, Pentax 55-300 DAL, Pentax DA 17-55, Pentax 35-80, Generic grip, Generic remote, Nissin Flash. HISTORY - MZ 50, MZ 60, *istDS, KM, K20D, Nikon F60, Nikon F90. Large assortment of Point and shoot film and Digital, Sigma 70-300 APO DG, Samyang 500mm mirror lens, Sigma lenses of all assortments. K20D now sold. Sad to see it go, but makes room for an eventual upgrade to the K5 or the K4?

karma mechanic

Link Posted 28/07/2011 - 13:45
Is the light bulb pictures from the same position, or have you moved (lots) to keep it the same size in the picture? (I'm wondering whether the bulb is much smaller in the picture at 55mm so the AF has focussed on something else)

Are these pictures at the widest aperture?
My own website is www.richardgaddphotography.com

Also on 500px

surfseen

Link Posted 29/07/2011 - 01:13
Yes using spot focus and very careful to focus on the light bulb. But I have a feeling that ff and bf issues which seem to arise with the Kr may have someting to do with the accuracy of the spot focus.

Will have to retest outside with a focus sheet and a tripod.
Andrew
KR, Pentax 55-300 DAL, Pentax DA 17-55, Pentax 35-80, Generic grip, Generic remote, Nissin Flash. HISTORY - MZ 50, MZ 60, *istDS, KM, K20D, Nikon F60, Nikon F90. Large assortment of Point and shoot film and Digital, Sigma 70-300 APO DG, Samyang 500mm mirror lens, Sigma lenses of all assortments. K20D now sold. Sad to see it go, but makes room for an eventual upgrade to the K5 or the K4?

Smeggypants

Link Posted 29/07/2011 - 02:37
Don't need a tripod. Just do some test shots on a sheet of paper with some print on at an angle.
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

thoughton

Link Posted 29/07/2011 - 10:11
surfseen wrote:
Always looking for the sharpest possible photo. Under the Custom settings No 21. Does the fine adjustment only affect the current lens, or any lens attached to the camera.

Taking pictures of a light bulb inside, with the built in flash using the 55-300 pentax lens. The bulb comes out sharp at the 300mm, but at 55mm it is not as sharp. Any ideas of what the cause would be.

On the K5 the fine adjustment can be saved for up to 10 individual lenses. There is also a seperate 'global' setting. I believe the K-r works the same way. Not too sure what happens when the camera can't ID the lens properly, like some Sigma lenses.

AF adjustment for zooms is always a bit problematic in my experience. It doesn't seem too unusual for it to FF slightly at one end, while BFing slightly at the other end. That was the case with both my Tamron 17-50 and my Sigma 70-200. I just chose a midpoint for the AF adjustment, and things seem to be okay.

There are downloadable focus test charts you can find on Google which might be useful. In particular there is a solid black/white target in the middle to ensure the camera AF is always focussing on the same thing.
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
Last Edited by thoughton on 29/07/2011 - 10:12

surfseen

Link Posted 29/07/2011 - 12:03
I have a "perfect-pixs" focus chart. So far only tried it under tungsten light. A bit useless. On the Pentax 55-300, it works really well at the 300mm. The focus is spot on with the depth of field extending on both sides about the same distance. On my Pentax 35-80, it works really well at the 80mm and again, the centre point is in focus and the depth of field extends about equally before and after.

But at the 55mm and the 35mm, the result is not good, not as well focussed and the depth of field is forward. I really couldnt get close enough to really get a good point to focus on. I think that this is the limitation of the focus chart. Unless you can get one in A1 size.

Will try again tomorrow with some bottles lined up in the sun, to see how it goes.
Andrew
KR, Pentax 55-300 DAL, Pentax DA 17-55, Pentax 35-80, Generic grip, Generic remote, Nissin Flash. HISTORY - MZ 50, MZ 60, *istDS, KM, K20D, Nikon F60, Nikon F90. Large assortment of Point and shoot film and Digital, Sigma 70-300 APO DG, Samyang 500mm mirror lens, Sigma lenses of all assortments. K20D now sold. Sad to see it go, but makes room for an eventual upgrade to the K5 or the K4?

SteveEveritt

Link Posted 29/07/2011 - 18:10
I think if you set it to focus at 55 you might lose the sharpness at 300 and I would wager you will use the long end of the lens way more than the short as 55 is covered elswhere. Just my thoughts.
Steve
My Flickr link

"Life is what happens to you while you're busy making other plans" (John Lennon)

surfseen

Link Posted 29/07/2011 - 22:40
I thought the 55-300 would be a versatile lens. But if I have focus issues at 55. The lens effectively is probably a 150-300.
Andrew
KR, Pentax 55-300 DAL, Pentax DA 17-55, Pentax 35-80, Generic grip, Generic remote, Nissin Flash. HISTORY - MZ 50, MZ 60, *istDS, KM, K20D, Nikon F60, Nikon F90. Large assortment of Point and shoot film and Digital, Sigma 70-300 APO DG, Samyang 500mm mirror lens, Sigma lenses of all assortments. K20D now sold. Sad to see it go, but makes room for an eventual upgrade to the K5 or the K4?

Smeggypants

Link Posted 29/07/2011 - 23:22
thoughton wrote:


On the K5 the fine adjustment can be saved for up to 10 individual lenses. There is also a seperate 'global' setting. I believe the K-r works the same way. Not too sure what happens when the camera can't ID the lens properly, like some Sigma lenses.


20



[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

surfseen

Link Posted 31/07/2011 - 00:44
Tested the KR outside with some focus tests, using a row of bottles.

There are still some issues with (let me get this the right way around)the Kr focussing at a spot in front of the centre. Is that ff or bf? But only with the zooms at the lowest zoom level. But perfectly acceptable. Wouldnt like to AF fine adjust then would put the upper zoom out.

I think that you could correct if necessary for prime lenses. I cant test for that because I havent got any prime lenses.

There is a lesson here for me to learn. When taking photos dont use the zoom lenses at the bottom zoom if you can avoid it.

Any one else had these experiences or is it just my camera.

I would be interested to hear if the k5 has any issues like these, before my eventual upgrade one day.
Andrew
KR, Pentax 55-300 DAL, Pentax DA 17-55, Pentax 35-80, Generic grip, Generic remote, Nissin Flash. HISTORY - MZ 50, MZ 60, *istDS, KM, K20D, Nikon F60, Nikon F90. Large assortment of Point and shoot film and Digital, Sigma 70-300 APO DG, Samyang 500mm mirror lens, Sigma lenses of all assortments. K20D now sold. Sad to see it go, but makes room for an eventual upgrade to the K5 or the K4?

johnriley

Link Posted 31/07/2011 - 08:31
Not knowing how you went about this, it strikes me that at the long end the camera has an easier job of focusing with the limited DOF available. At the wide end it's harder to find the point of focus. This is true for our eyes as well, when we manually focus.

However, at the wider end the increased DOF covers up any small focusing errors.

I suspect that there's some other reason for your findings.

Try photographing a newspapoer pinned to a wall. Use a tripod and make sure the camera back is parallel. Fill the frame at the wide angle end and see which text id sharp. Bear in mind though that curvature of field may mean that at wide apertures the centre can be inj focus but not the edges, and vice-versa.

There's no reason to avoid using the wide end of zoom lenses. You might as well have a fixed focal length if this was so.
Best regards, John

wvbarnes

Link Posted 31/07/2011 - 09:47
I have a KR with 10mm through to 300mm (15 to 450mm equiv) in my three lens kit.

I use spot focus a lot with my telephoto and accept that you can only expect so much from autofocus when depth of field is shallow and it is so easy to mistakenly focus on a leaf or twig when trying to get a bird, butterfly or insect for example.

At extreme wide angle many lenses are documented as being difficult for the in camera focus system (not just Pentax)

I think the KR has only one setting for all lenses focus adjustment. I've not used it, dared to or had to.

I'm amazed how few people mention using the quick focus ring over-ride on DA lenses or indeed simply switching to manual with difficult subjects.

I also note reading around other photography sites and mags that supposed focus AF inaccuracy is the new obsession. Isn't this in danger of becoming a little sad?

Going out/ travelling abroad with camera and enjoying my photography is mine! Now where are those damned butterflies today??????

johnriley

Link Posted 31/07/2011 - 10:09
Quote:
I also note reading around other photography sites and mags that supposed focus AF inaccuracy is the new obsession. Isn't this in danger of becoming a little sad?

It is indeed the current obsession. I find it hard to get excitred about it because I've not found a lens with a problem yet, and that covers a large number of lenses. When I see written that all the lenses someone has have needed adjustment then I would wonder why that was. Technique? Misunderstanding of the testing process? Incredible bad luck? Faulty camera body?

Manyfacturers have added this feature after it became obvious people were accessing the hidden menus anyway...so little development cost there.

Is there a general problem? If your pictures are sharp, then no. If they are not sharp, then look to technique first before assuming AF errors. And no alternative focusing screens and other adaptations to confuse the issue.

I still think messing with the innards of cameras is best left to the properly equipped technicians.
Best regards, John

Anvh

Link Posted 31/07/2011 - 13:16
johnriley wrote:
Manyfacturers have added this feature after it became obvious people were accessing the hidden menus anyway...so little development cost there.

I thought Pentax brought it to the K20D because the higer end camera's from other brands also had it.
First time hearing that we are to blame.

About the AF errors, when trying out new lenses i did notice that the AF just wasn't bang on when i saw the photos at home but they were with my calibrated lenses so i know that calibration can make a differnce.
Silly enough i focus most of the time manually so i didn't notice it at first.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

johnriley

Link Posted 31/07/2011 - 13:24
As I recall Pentax were actually one of the first on this occasion, and the others soon followed.

Just another feature to compete against each other with? Or a real problem finally addressed?

Now that high ISO noise seems to be tackled and pixels counts are about as high as needed or practical it will come back to camera handling and whichever model we find "gels" with an individual.
Best regards, John
Add a Comment
You must be registered or logged-in to comment.