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04-08-2014, 11:23 AM   #16
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re: your first image:
The camera back is not parallel with the group. Your group therefore does not coincide with the plane of sharp focus. Look at the green line on the floor in the foreground; it is parallel to the group. There is not enough depth of field at f4 to cover this discrepancy.

04-08-2014, 11:53 AM   #17
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I will be very surprised if this lens doesn't end up being defective.
04-08-2014, 12:02 PM   #18
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Original Poster
QuoteOriginally posted by johnyates Quote
re: your first image:
The camera back is not parallel with the group. Your group therefore does not coincide with the plane of sharp focus. Look at the green line on the floor in the foreground; it is parallel to the group. There is not enough depth of field at f4 to cover this discrepancy.
I am sorry for being so blunt, but do you actually know what you are talking about?

I am not an expert at this calculation, but if I am not completely missing something...

aperture: f/4
focal length: 26mm
distance to subjects: ~4m (probably more)
APS-C sensor size

That results in a DOF of about 4.5m. That means, the near limit should be about 1.2m in front of the point of focus. If we assume, the point of focus is the face of the girl in the middle, the girl on the very right would have to be more than 1.5m in front of the focal plain (probably more like 1.8m) for this kind of blurring. The tiles on the floor are 1m by 1m. I have not measured this, but I would say the focal plain is at most 30cm further to the back on the right side - and with that well within the DOF. Please also remember that the girls on the right are further away from the camera than those in the middle and this would reduce the distance to the focal plain a little.

No offence, but I think that shot was a miss.

Regards,
Chris

---------- Post added 04-08-14 at 09:05 PM ----------

Hey everyone!

As requested, I set up my camera on a tripod after work today and took a few test shots. Actually hitting the 26mm focal length (to get the same results as to the end of the tournament) wasn't too easy, but I did it. This is the result:

http://media.advico.de/photo/misc/boring_wall.jpg

I can still see an ugly blur on the right.

Regards,
Chris
04-08-2014, 12:15 PM   #19
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QuoteOriginally posted by PixelGeek Quote
I can still see an ugly blur on the right.
Oh Yes,
I think you will be taking more of those happy photos when you get a decent lens.

I have been down at the school gym taking the kids with my newly restored SMC Pentax 1:2.8 24mm. Very sharp.
I mean the lens, but the kids were too.

04-18-2014, 09:38 AM   #20
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QuoteOriginally posted by PixelGeek Quote
I am sorry for being so blunt, but do you actually know what you are talking about?

I am not an expert at this calculation, but if I am not completely missing something...

aperture: f/4
focal length: 26mm
distance to subjects: ~4m (probably more)
APS-C sensor size

That results in a DOF of about 4.5m. That means, the near limit should be about 1.2m in front of the point of focus. If we assume, the point of focus is the face of the girl in the middle, the girl on the very right would have to be more than 1.5m in front of the focal plain (probably more like 1.8m) for this kind of blurring. The tiles on the floor are 1m by 1m. I have not measured this, but I would say the focal plain is at most 30cm further to the back on the right side - and with that well within the DOF. Please also remember that the girls on the right are further away from the camera than those in the middle and this would reduce the distance to the focal plain a little.

No offence, but I think that shot was a miss.

Regards,
Chris

---------- Post added 04-08-14 at 09:05 PM ----------

Hey everyone!

As requested, I set up my camera on a tripod after work today and took a few test shots. Actually hitting the 26mm focal length (to get the same results as to the end of the tournament) wasn't too easy, but I did it. This is the result:

http://media.advico.de/photo/misc/boring_wall.jpg

I can still see an ugly blur on the right.

Regards,
Chris
Yep I think the lens is de-centered badly.

It was an achilies heel of this lens in the first few months of production, I guess they stil make em bad occasionally
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