Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-14-2009, 06:27 AM   #16
Site Supporter
tomwil's Avatar

Join Date: May 2009
Location: Maryland USA
Posts: 778
QuoteOriginally posted by imtheguy Quote
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)

10-14-2009, 06:49 AM   #17
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
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.
10-14-2009, 09:03 AM   #18
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 15,107
QuoteOriginally posted by Ash Quote
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.
10-14-2009, 10:38 AM   #19
Veteran Member
Fl_Gulfer's Avatar

Join Date: Jul 2007
Location: Florida Gulf
Photos: Albums
Posts: 3,033
Original Poster
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


Last edited by Fl_Gulfer; 10-14-2009 at 10:48 AM.
10-14-2009, 11:58 AM   #20
Senior Moderator
Loyal Site Supporter
Parallax's Avatar

Join Date: Apr 2008
Location: South Dakota
Photos: Gallery
Posts: 15,107
QuoteOriginally posted by Fl_Gulfer Quote
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.
10-14-2009, 01:39 PM   #21
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
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.
10-15-2009, 09:44 AM   #22
Veteran Member
Fl_Gulfer's Avatar

Join Date: Jul 2007
Location: Florida Gulf
Photos: Albums
Posts: 3,033
Original Poster
Here is the K100D with EXIF.




The K20D with EXIF


10-15-2009, 01:35 PM   #23
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
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.

10-15-2009, 03:08 PM   #24
Veteran Member
Fl_Gulfer's Avatar

Join Date: Jul 2007
Location: Florida Gulf
Photos: Albums
Posts: 3,033
Original Poster
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.

Last edited by Fl_Gulfer; 10-15-2009 at 07:56 PM.
10-17-2009, 04:40 AM   #25
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by Fl_Gulfer Quote
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.
10-17-2009, 10:01 AM   #26
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Fl_Gulfer Quote
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.
10-17-2009, 10:11 AM   #27
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,434
I'm surpried AF is even that close.

QuoteOriginally posted by Fl_Gulfer Quote
. 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

Last edited by jeffkrol; 10-17-2009 at 10:16 AM.
10-17-2009, 07:48 PM   #28
Veteran Member
Fl_Gulfer's Avatar

Join Date: Jul 2007
Location: Florida Gulf
Photos: Albums
Posts: 3,033
Original Poster
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.
10-17-2009, 11:10 PM   #29
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by jeffkrol Quote
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).

Last edited by Class A; 10-18-2009 at 12:08 AM.
10-18-2009, 12:12 AM   #30
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by Fl_Gulfer Quote
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.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, k100d, k20d, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
k20d problem Neto Pentax DSLR Discussion 2 09-24-2009 02:59 AM
K20D Problem photoTaz Pentax DSLR Discussion 2 06-21-2009 09:25 PM
Just got my K20D... problem already - need help! dimak Troubleshooting and Beginner Help 6 05-01-2009 04:21 AM
Card read problem K20d. Have you had this problem? rsi1986 Pentax DSLR Discussion 8 12-27-2008 05:25 AM
Problem with K20D eadnams Pentax DSLR Discussion 7 06-28-2008 07:21 AM



All times are GMT -7. The time now is 06:45 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top