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11-24-2010, 07:00 AM   #1
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K20d AND 'LIGHT CAST'

Recently I encountered a rather strange light cast (I don't know the right translation for "overstraling") when shooting very high light values next to darker ones in Morocco, lots of 'strong' sun over there. In the attached example you can seen it around the outer part of the arch, somewhere in the middle of the picture, and in the back ground too, they are square formed white blotches.

Anny clue what might be cause?


Last edited by philippe; 01-14-2011 at 01:09 AM.
11-24-2010, 07:58 AM   #2
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If you've checked for smears on the lens, have you tried a different lens to see if this problem is still there too? It might (but probably not) be a smear on your sensor or mirror, but it looks like a lens problem to me.
11-24-2010, 08:29 AM   #3
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Chalion, thank you for the swift reaction,
I always check my lenses for smears, almost intuitively. And I always carry my lenses with the cap on it, I do not like filters for protection as they cause troubles, namely in this kind of light conditions.
This is shot with the DA 15 mm, F 8 or 11, and with the DA 21mm I encountered the same issues, more or less, and not for the first time.
When viewed at 100% these blotches look square shaped and always aligned with the vertical and horizontal axis, checker like. Lens blur, due to smear, has most of the time irregular (hazy) forms.
11-24-2010, 08:35 AM   #4
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Looks like dirt on your sensor.

11-24-2010, 10:11 AM   #5
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No, because the other pictures token that day, just before and after these series, had no sensor like problems. It is particularly in this kind of shooting situation, strong light contrasts, that these square 'blotches' are appearing. I had them in Spain too about a month earlier but was not alerted because I thought that it cold be due to lens flair, a dirty sensor or just me.
During this shooting in Morocco, and remembering the earlier experiences, I spend some more attention to the state of the lens and sensor...
No, definitely, I must be overlooking something!
11-24-2010, 07:46 PM   #6
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Do you shoot with a UV filter on the lens?

Sometimes they can cause reflections of the sensor back onto the sensor.

Although I've never seen this in bright light, only high contrast night scenes.
11-25-2010, 06:54 PM   #7
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Do you have dynamic range enabled? Maybe the brightness has "confused" the sensor?

How about noise reduction?

White can cause reflection in huge amounts, was a hood used?

I'm no expert so please don't flame me for these questions.
11-25-2010, 09:39 PM   #8
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It's flare, but because there is no point source of light in or near the picture it is softer, more like a combination of veiling flare and point source flare.
It could be from the lens, or it could also be reflections from the sensor off the rear lens element.

11-27-2010, 10:58 AM   #9
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QuoteOriginally posted by fccwpe Quote
Do you have dynamic range enabled? Maybe the brightness has "confused" the sensor?

How about noise reduction?

White can cause reflection in huge amounts, was a hood used?

I'm no expert so please don't flame me for these questions.
Sorry if I flamed on somebody, it was never my intention if I it looked like that...
No, I did not had Dynamic Range enabled, no NR and the hood was pulled out. Actually, I do not use these in-body 'things', just natural and simple in RAW at 5500K and bracketing, bracketing and more than ever bracketing...

Last edited by philippe; 11-28-2010 at 02:00 AM.
11-27-2010, 11:02 AM   #10
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QuoteOriginally posted by Wheatfield Quote
It's flare, but because there is no point source of light in or near the picture it is softer, more like a combination of veiling flare and point source flare.
It could be from the lens, or it could also be reflections from the sensor off the rear lens element.
Could indeed be, but I thought that DA lenses where particularly 'treated' against these kind of reflections...
11-27-2010, 12:38 PM   #11
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QuoteOriginally posted by philippe Quote
Recently I encountered a rather strange light cast (I don't know the right translation for "overstraling") when shooting very high light values next to darker ones in Morocco, lots of 'strong' sun over there. In the attached example you can seen it around the outer part of the arch, somewhere in the middle of the picture, and in the back ground too, they are square formed white blotches.

Anny clue what might be cause?
Looks like flare but it's hard to see at this size.
Any chance you could post a full size sample?
11-28-2010, 01:58 AM   #12
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here is the crop.
I tuned the contrast and density a little to make it somewhat clearer.
One can see that in area's A and C the shape is very rectangular and regularly.
If it was flair, of any kind, it would not be so 'structured' nor systematic.
It is as it fits in to a grid and only a few of the blocs of this grid are blurred.

Last edited by philippe; 01-14-2011 at 01:09 AM.
11-28-2010, 02:48 AM   #13
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It looks like condensation to me. Did you walk out of an airconditioned room, into a humid warm day?
11-28-2010, 05:31 AM   #14
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QuoteOriginally posted by adamaitken Quote
It looks like condensation to me. Did you walk out of an airconditioned room, into a humid warm day?
No, not at all, no airco. This is old Taroudannt and the houses are made of adobe, airco seems to be destructive for adobe houses. Actually, they do not need it at all, these houses are always pleasant to stay in, winter and summer.
11-28-2010, 06:56 AM   #15
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How about the Vague Theory Sensor Bloom ?
It's mentioned here and there, but good examples are hard to come by.
My understanding of it is that when the photo sites are over exposed, additional light 'Bleeds' over to surrounding sites. Example is Bright Whites smearing over to the darks. IIRC some folks equal it to a form of CA.
I mention this because you have detail in the shadows and the Bright Walls are over exposed. Read this link...and sub links.

How to differentiate Sensor Bloom and CA.::Manual Focus Lenses

Good Luck.
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