Extensive focus Tests with 3 different Lenses.
Posted 23/05/2009 - 15:02
Link
Your too far away from the test chary with the 50mm Craig. If you get say .45m away it will be more obvious like this:
[IMG]http://i545.photobucket.com/albums/hh387/penbx/FocusTest.jpg[/IMG]
I can't see which way the adjustment is getting better, you need to be at 45deg to the chart and it looks like +-10 isn't enough. Will the K20D go to +-20?
The box shots are getting worse at 400mm but that might just be DOF.
shim
[IMG]http://i545.photobucket.com/albums/hh387/penbx/FocusTest.jpg[/IMG]
I can't see which way the adjustment is getting better, you need to be at 45deg to the chart and it looks like +-10 isn't enough. Will the K20D go to +-20?
The box shots are getting worse at 400mm but that might just be DOF.
shim
Posted 23/05/2009 - 15:06
Link
Craig to me the 16-45 @f4 chart is the-10 I would set at _8.
At 400 f5.6 -10 not enough, I would settle for the 16-45 at around -8ish but would send the 400mm lens back, but in saying that the 50mm f1.4 is not good, so I would still suspect your camera has a fault as well.
At 400 f5.6 -10 not enough, I would settle for the 16-45 at around -8ish but would send the 400mm lens back, but in saying that the 50mm f1.4 is not good, so I would still suspect your camera has a fault as well.
Tel,
Posted 23/05/2009 - 15:14
Link
The 50mm at plus 10 is OK.... so it's not the camera. The other two 50mm shots are just not in focus or have camera shake.
You need to get the 400mm sorted out and then take a shot of the box filling the frame at f/5.6 and then another with the 50mm filling the frame (with +10) setting and at f/5.6 or f/8 to give you a good depth of field and compare the two.
shim
You need to get the 400mm sorted out and then take a shot of the box filling the frame at f/5.6 and then another with the 50mm filling the frame (with +10) setting and at f/5.6 or f/8 to give you a good depth of field and compare the two.
shim
Posted 23/05/2009 - 15:26
Link
shim wrote:
The 50mm at plus 10 is OK.... so it's not the camera. The other two 50mm shots are just not in focus or have camera shake.
You need to get the 400mm sorted out and then take a shot of the box filling the frame at f/5.6 and then another with the 50mm filling the frame (with +10) setting and at f/5.6 or f/8 to give you a good depth of field and compare the two.
shim
Shim they are in focus and were mounted on a tripod with SR off and using the 2 second timer.The 50mm at plus 10 is OK.... so it's not the camera. The other two 50mm shots are just not in focus or have camera shake.
You need to get the 400mm sorted out and then take a shot of the box filling the frame at f/5.6 and then another with the 50mm filling the frame (with +10) setting and at f/5.6 or f/8 to give you a good depth of field and compare the two.
shim
Minus 10 is pretty decent on the 50mm although i suspect minus 13 to 15 would be spot on but it dosent go that far.
Posted 23/05/2009 - 17:19
Link
Craig,
Please forgive me for asking a what may be stupid question.
Are you tilting the focus adjustment chart at 45 degrees to the axis of the lens (i.e. is the back focus end of the chart farther away than the front focus end)?
I ask this because in the focus chart pictures the front and back focus chart is of a constant width, but if a constant width chart were at 45 degrees to the lens axis then it would appear to taper in the pictures.
Please forgive me for asking a what may be stupid question.
Are you tilting the focus adjustment chart at 45 degrees to the axis of the lens (i.e. is the back focus end of the chart farther away than the front focus end)?
I ask this because in the focus chart pictures the front and back focus chart is of a constant width, but if a constant width chart were at 45 degrees to the lens axis then it would appear to taper in the pictures.
Good luck
Bob
Pentax user since 1978, Digital since 1997.
Kit includes: K-7, K20D, K10D, *istDS, full set DA* lens, etc
Bob
Pentax user since 1978, Digital since 1997.
Kit includes: K-7, K20D, K10D, *istDS, full set DA* lens, etc
Posted 23/05/2009 - 17:42
Link
Craig,
Forget that chart, it's much too busy/fussy/noisy at the most critical focus point.
Use these instead. Each of them has exactly one high contrast boundary for focussing, unlike your charts. Chose the one appropriate to the lens you are testing.
For best results they should be printed on card for stiffness. I use Fujifilm photographic card (270gsm).
The charts must be angled at 45 degrees to the focussing plane, and the centreline of the focus target should be level with the centre of your lens otherwise your results are meaningless.
Use a hot shoe mounted spirit level (or some other means) to ensure the camera is level, then adjust the tripod height to match the height of the centreline of the chart.
Check out the authors blog about K20D focus adjustment here.
Forget that chart, it's much too busy/fussy/noisy at the most critical focus point.
Use these instead. Each of them has exactly one high contrast boundary for focussing, unlike your charts. Chose the one appropriate to the lens you are testing.
For best results they should be printed on card for stiffness. I use Fujifilm photographic card (270gsm).
The charts must be angled at 45 degrees to the focussing plane, and the centreline of the focus target should be level with the centre of your lens otherwise your results are meaningless.
Use a hot shoe mounted spirit level (or some other means) to ensure the camera is level, then adjust the tripod height to match the height of the centreline of the chart.
Check out the authors blog about K20D focus adjustment here.
Peter E Smith - flickr Photostream
Add Comment
To leave a comment - Log in to Pentax User or create a new account.
211 posts
17 years
Lanarkshire,
Scotland
First 3 are all the 120-400mm @ various ranges and at f5.6.
Focus Point on the First 3 was the Word Ingredients.
120mm
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/56120mm.jpg[/IMG]
148mm
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/56148mm.jpg[/IMG]
300mm
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/56300mm.jpg[/IMG]
400mm
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/56400mm.jpg[/IMG]
We will now move on to Focus Chart Tests using the Cameras Focus Compensation at 0, -10 and +10
All at 400mm f5.6
Focus Adjust at 0
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/400mmfocus0.jpg[/IMG]
Focus Adjust at -10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/400mmfocusminus10.jpg[/IMG]
Focus Adjust at Plus 10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/400mmfocusplus10.jpg[/IMG]
Next we have the Focus adjust at the 3 extremes using a 16-45mm @ f4.
Focus adjust at 0
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/16-4545mmfocus0.jpg[/IMG]
Minus 10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/16-4545mmfocusminus10.jpg[/IMG]
Plus 10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/16-4545mmfocusplus10.jpg[/IMG]
Next up we have the 50mm f1.4 @ the 3 extremes, these results alarmed me a little.
Focus @ 0
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/50mm14focus0.jpg[/IMG]
Minus 10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/50mm14focusminus10.jpg[/IMG]
Plus 10
[IMG]http://i271.photobucket.com/albums/jj132/CraigF1969/private/50mm14focusplus10.jpg[/IMG]
I appreciate any and all thought on these.
Thanks