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07-14-2009, 09:26 AM   #1
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K-7 and lens correction

I was having a problem with how long it took my K-7 to save and display images . Everybody kept saying it's faster than the K20D, but my experience showed otherwise. Then, I tried an old manual lens, and the image was saved in the blink of an eye. So I looked in the matter more deeply, and finally figured out that when "lens correction" and "chromatic aberration correction" are on, it takes a while to process everything. So, if you think your K-7 takes a while to save an image, check for those two options first.

07-14-2009, 09:37 AM   #2
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Hmmm.. great find!!!
07-14-2009, 10:26 AM   #3
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Yves, does this feature correct RAW files as well as JPEGs? I posted an earlier query, but got no response.

Thanks,

Jer
07-14-2009, 10:31 AM   #4
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QuoteOriginally posted by flyer Quote
I was having a problem with how long it took my K-7 to save and display images . Everybody kept saying it's faster than the K20D, but my experience showed otherwise. Then, I tried an old manual lens, and the image was saved in the blink of an eye. So I looked in the matter more deeply, and finally figured out that when "lens correction" and "chromatic aberration correction" are on, it takes a while to process everything. So, if you think your K-7 takes a while to save an image, check for those two options first.
It also cuts your buffer size down to five shots.
Shades of the *istD!!!

07-14-2009, 12:07 PM   #5
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I second Sailor's question. Does the delay also exist when the camera is in RAW mode? How does the correction work with RAW? I would love to use the correction feature to save on pp time, but not at the cost of a 5-frame buffer (the buffer size and inability to change settings while clearing buffer is my number 1 pet hate of my current k100d).

I would assume the camera basically has a database of lenses+focal lengths and their distortion profiles in memory and applies a corresponding transformation to the image - for a RAW file these correction factors could just be stored in the metadata and the actual tansformations done on a computer.
I recall seeing a post about how the new Lightroom version (or was it ACR?) supports this kind of correction data, and it would make most sense to me to do it this way.
07-14-2009, 12:29 PM   #6
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QuoteOriginally posted by PolishMike Quote
I would assume the camera basically has a database of lenses+focal lengths and their distortion profiles in memory and applies a corresponding transformation to the image
According to JohnCPentax, the data is actually in the lens. This is why the auto-correction features only work with DA & D-FA lenses. The older lenses do not have the necessary information embedded in them.

Mind you, this does not mean the correction data could not be written to the RAW file anyway.
07-14-2009, 02:42 PM   #7
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QuoteOriginally posted by Sailor Quote
Yves, does this feature correct RAW files as well as JPEGs? I posted an earlier query, but got no response.

Thanks,

Jer
The delay is there in RAW as well as in JPEG mode. AND, as stated by somebody else, it fills the buffer and keep your RAW "machine gun" to five pictures. If yuo use the corrections in movie mode, it also cuts on your shooting time, and it takes forever to clear the buffer. To use only when you're in no hurry. To me, it looks like it marks the RAW files, so Pentax utility will apply the corrections.
07-14-2009, 02:59 PM   #8
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If performance is important maybe it's a good idea to turn off in-camera lens correction and use something like PTlens - great piece of software BTW

Simon

07-15-2009, 03:17 AM   #9
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Yeah, Simon, that would be an alternative. It is a shame though, since the delay means I will definitely not use a feature I would otherwise find quite useful, and one which would simplify my workflow (I normally do not bother with lens corrections, since it takes an extra bit of software outside Lightroom, but it would be nice to have them handled automatically)
07-15-2009, 03:56 AM   #10
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On the other hand, as I mentioned previously, the camera will instantly respond to the shutter and take a picture even when processing for lens distortion. So the delay isn't as bad as it seems.
07-15-2009, 04:23 AM   #11
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QuoteOriginally posted by mattdm Quote
On the other hand, as I mentioned previously, the camera will instantly respond to the shutter and take a picture even when processing for lens distortion. So the delay isn't as bad as it seems.
It all depends on how many pictures are being processed. If you want to do HDR with seven pictures in one burst, you'll have to wait for the buffer to clear partially after five pictures.
07-15-2009, 05:24 AM   #12
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QuoteOriginally posted by flyer Quote
It all depends on how many pictures are being processed. If you want to do HDR with seven pictures in one burst, you'll have to wait for the buffer to clear partially after five pictures.
Only if shooting raw, right? And if you're shooting raw, no point in doing heavy processing like this in-camera. I admit I haven't tested since I don't really use burst.
07-15-2009, 05:48 AM   #13
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QuoteOriginally posted by mattdm Quote
Only if shooting raw, right? And if you're shooting raw, no point in doing heavy processing like this in-camera. I admit I haven't tested since I don't really use burst.
The problem is there in RAW too. I just tried it, and the camera took four pictures in rapid succession, then it took about three to four seconds before it took the fifth in a five exposure bracket with lens correction and chromatic aberration correction on.

Last edited by flyer; 07-15-2009 at 03:48 PM. Reason: Noticed I wrote JPEG instead of RAW. I'm sorry for the inconvenience.
07-15-2009, 05:59 AM   #14
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The reason why RAW file save times are also impacted is probably that the camera performs the corrections to generate the embedded JPG.

Parameters are also included in the RAW file EXIF that allow the Pentax software to treat the RAW data in development. I don't know whether these parameters are derived from the calculations or are just a copy of the data from the lens. In the latter case, it would seem logical that these parameters could be included in the RAW file EXIF regardsless of the option being checked or not.

Can someone shed light on this?

Wim
07-15-2009, 02:07 PM   #15
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QuoteOriginally posted by flyer Quote
The problem is there in JPEG too. I just tried it, and the camera took four pictures in rapid succession, then it took about three to four seconds before it took the fifth in a five exposure bracket with lens correction and chromatic aberration correction on.
Thanks Yves

I must take a look myself... very useful info


Neil
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