[tomwil]

It better not have engaged on a tripod mounted, remote fired shot.

According to the Exif data, it does seem that SR was on, on at least one camera, with varying results:

K100D:

SR Focal Length 300 mm
SR Half Press Time 0.22 s
SR Result Not ready
Shake Reduction On

K20D:

SR Focal Length 300 mm
SR Half Press Time 0.00 s
SR Result Not ready
Shake Reduction Unknown (15)

[Lowell Goudge]

I think what is shown is a difference between camera "auto everything" settings

I took the K20 photo, lightened it, corrected color balance for poor white balance and increased saturation and achieved very close to the same image as shot with the K100D.

[Parallax]

Then the results are just not comparable.
Green mode takes over far too many variables - or perhaps the comparison is between two green modes from two different cameras...

Either way, there's no 'problem' with the K20D from what we see here.

"Green Mode" is the absolute antithesis of Occam's Razor.

[Fl_Gulfer]

Ok what settings should I use for a Bright Sunny day and what should I take a photo of so you can see the focus problem instead of the lightning.
I will use a tripod and wired switch.
And which lens TAMRON SP 17-50/2.8 Di II & AF 1.4X MC4 TC
SIGMA EX 100-300/4 APO DG
SIGMA EX 105/2.8 DG Macro

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Last edited by Fl_Gulfer; 10-14-2009 at 10:48 AM.

[Parallax]

Ok what settings should I use for a Bright Sunny day and what should I take a photo of so you can see the focus problem instead of the lightning.
I will use a tripod and wired switch.
And which lens TAMRON SP 17-50/2.8 Di II & AF 1.4X MC4 TC
SIGMA EX 100-300/4 APO DG
SIGMA EX 105/2.8 DG Macro

Try the "rule of 16" With the camera set at f16 the shutter speed should match ISO. I would suggest setting your ISO to 200, f stop to f8 and shutter speed to 1/750th and shake reduction off if you are using a tripod.

[Marc Sabatella]

Basically, shoot in M mode and make sure the same ISO, aperture, and shutter speed are used for both; also be sure use the same focus point is used for both cameras. And use a target that has only one clear thing to focus on within range of that focus point.

[Fl_Gulfer]

Here is the K100D with EXIF.




The K20D with EXIF

[Marc Sabatella]

Looks like the K20D could be front or backfocusing with this particular lens; you might consider a test using a good chart like the one at focustestchart.com. Luckily, unlike with the K100D, it would be very simple to use the AF fine adjustment menu to work around this.

[Fl_Gulfer]

I used the chart like it said and I had to go to -10 and it still needs to go a couple more to be perfect. Thats on my Tamron 17-50 2.8. I haven't tryed my Macro lens yet. But dosen't that seam extream??

This is a large photo!! so you can see how far off the focus is at -10 and it still needs more.

[Class A]

Here is the K100D with EXIF.

The K20D with EXIF

If the K20D were front focusing the table should be sharper than in the K100D shot, but it doesn't seem to be.

The K100D shot shows some JPEG artefacts around the writing on the box. The K20D shot doesn't.

Could there be a difference in camera settings regarding JPEG quality and/or sharpness?

Could there be a problem with the resizing of the K20D shot? Some programs do not do a great job of downscaling while retaining detail.

[Marc Sabatella]

I used the chart like it said and I had to go to -10 and it still needs to go a couple more to be perfect. Thats on my Tamron 17-50 2.8. I haven't tryed my Macro lens yet. But dosen't that seam extream??

What kind of light did you shoot this in? If under tungsten light, then I'd say you've already gone far enough, and very possibly too far, since it is normal for tungsten light to induce a bit of front focus. It might well turn out that you're backfocusing now in more well-balanced light. You should test with a variety of lenses and in different light to find good compromise settings. But I'd say that this image shows that worst case scenario, you should be able to dial in the -10 and get decent results with this lens.

[jeffkrol]

. But doesn't that seem extreme??

nice little summary of AF (Pentax AF module is actually in the bottom of the camera)
June 2009: Removing the Blindfold from the dSLR
Background Last month I discussed the new Micro Four Thirds format being offered in cameras such as the Panasonic G1 and GH1. Note that Olympus/Panasonic have used Four Thirds format for years, it's the "Micro" part that makes Micro Four Thirds interesting as it removes the mirror mechanism from the camera. Last month it was merely a promising technical curiosity but this month I got my hands on a G1 and this new technology has become much more than just a curiosity. Right away I started noticing what a dSLR can do when there is no blindfold (mirror) obstructing the main sensor for important operations like focus, metering, and framing. Of course, when you remove the mirror from the dSLR, it is no longer technically a dSLR but such a camera still feels and operates very much like a dSLR with some very interesting added perks! Let's take a look at what a dSLR style camera can really do when you remove the mirror and open the camera's eye to the world it is about to photograph. Focus Traditional dSLR: It might seem like an odd statement but as far as focus, the traditional dSLR is handicapped at the starting line! When you activate a dSLR's auto-focus, you can see through the lens but the primary sensor (the sensor that is about to capture your image) is completely blind to what you are about to shoot. Instead, light is bounced into a secondary focus mechanism near the top of the camera that performs some phase based calculations to calculate where the focus ring on the lens should be turned in order to achieve proper focus. Due to slack in the lens' servo mechanism and slight errors caused by the positioning of the focus mechanism and lens, focus on a traditional dSLR is based on prediction only. When the mirror is flipped out of the way and the shutter is opened, slight errors in the prediction can sometimes cause auto-focus errors. This is why we hear so much talk about people getting their lenses calibrated to their camera bodies. Seldom do a lens/body pair match so perfectly that you get perfect focus for the entire zoom range (on a zoom lens).


June 2009: Removing the Blindfold from the dSLR

[Fl_Gulfer]

I used a FML Lamp to light the paper, It's like a florecent light but only 27 watts. It's a new reading lamp.
Maybe my 45 degree is off a little.

[Class A]

Due to slack in the lens' servo mechanism and slight errors caused by the positioning of the focus mechanism and lens, focus on a traditional dSLR is based on prediction only. When the mirror is flipped out of the way and the shutter is opened, slight errors in the prediction can sometimes cause auto-focus errors.

Nonsense!

There is a disadvantage associated with DSLR AF which is that if there is misalignment between the sensor and the AF system, there will be misfocus. But a properly calibrated camera does not have that problem.

Another potential problem is that the AF system sees something else than the sensor (due to colour temperature -> a problem the K-7 no longer has, or due to spherical aberration).

[Class A]

I used a FML Lamp to light the paper, It's like a florecent light but only 27 watts. It's a new reading lamp.
Maybe my 45 degree is off a little.

Try the same test using daylight. Pentax DSLRs before the K-7 are sensitive to the colour temperature.

The precision of the tilt is not critical at all. Any angle that allows you to see the change in sharpness will do.

It is, however, critical to make sure you focused on the middle focus target. The AF sensors are rather large so try to get a bit closer or use a longer FL. Ideally the camera should not be able to lock focus if you aim above or below the focus target. If it doesn't you are sure that it locks on the target rather than something to the side of it.