Chromatic Abberation for RAW Files?

This has all kicked off nicely. Thanks for all the ideas everybody. If I could summarise what I have gained regarding the original CA / DC question :

It appears that what we are saying is that the processing that occurs in camera with these functions active (as evident by the slower display on the LCD) is only being applied to the embedded jpg, and is not recorded with the RAW file. So for me at present, even though I have these functions on, I am not getting any Chrom Abberation or Distortion Correction on my photos.

If I want to have these corrections I can open the RAWs in Pentax Camera Utility (or another Converter software that supports the lenses such as Lightroom)and apply them manually. I believe people are saying that the in camera processed settings cannot be automatically applied to the RAWs in the software? If this is so, it seems odd to me that Pentax allow the settings to activate when the camera is set to record RAW only - surely there is no point in having these corrections applied to a jpg preview that will only be seen on a 3 inch screen?

I'll get the disc out again and try the Pentax software for this. I was interested in what Smeggy said about the storing of the correction settings after editing in a RAW converter - ACR allows for either the data to be written to the main file or in a seperate sidecar, but I understood that the recorded settings would only be for the specific adjustment parameters that each particular RAW converter has (eg vibrance, clarity, luminance noise etc); therefore when reopening the RAW file in that same converter the software will just reset all the sliders as recorded, effectivly reprosessing the file again.

I am not aware that this settings data would have any affect in a different converter - each new converter you open the file in will start off with its default profiles until you change the sliders, then those changes are recorded just as in the previous software.

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K7 with BG4 Grip, Samyang 14mm f2.8, DA18-55 WR, 'A' 28mm f2.8, 'K' 75-150 f4.0, Tamron Adaptall 135mm f2.8, AF280T flashgun, Pentax 2X teleconverter, remote control unit

I'm not 100% sure, maybe someone can confirm or deny? I only tend to do very basic processing in the Pentax software, then save the file out as a TIFF or JPEG and finish the processing in other applications.

Regards
David

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I'm not sure that is true.

As far as I am aware, RAW images, either .DNG or .PEF are effectively read only and can't be edited.

RAW conversion s/w needs to know how to de-mosaic the raw file. I'm not sure that they are clever enough to be able to re-write a mosaic'd file.

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Peter E Smith

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There might be some confusion here.

Develop settings and meta data can either be written as a sidecar file or embedded in the RAW file itself. If written in the RAW file it wouldn't change the raw data, but just add the settings as an extension in the file.

What particular software does I'm not sure.

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Correct - as far as image is concerned. But...


AFAIK, the Pentax Camera Utility does apply the in-camera settings automatically to the RAW

Pentax have built a very close link between the camera settings and the RAW converter. Others cannot easily match this since they have to cope with a myriad of different cameras and models, and not all embedded EXIF information (like the custom manufacturer data) is not public knowledge

It works like this - the camera records a TON of data about the shot and settings. Most RAW converters will take the basic cues from this EXIF data (like lens type, ISO, etc) to make automatic adjustments. Some of this EXIF data is Pentax-specific and difficult to work out what it means (unless you are Pentax ). So... Pentax's RAW converter takes a look at the full EXIF data and models itself as closely as possible to the camera settings as a starting point - and that's where you'll get the most consistent colour rendition between RAW and JPG (but not necessarily the most flexible work flow or creative options).

Lightroom is very nearly automatic - if you have a lens that's been profiled - but any extra CA (like the more difficult axial CA) needs to be done manually... but it takes 2 seconds.

Personally, I'd set up a test scenario: wide angle, backlit fine detail on the edges (like trees) and push a shot so that CA is obvious. Then shoot with and without CA adjustment in camera. Bring the two RAW files into Google Picasa (it's free and doesn't do CA adjustment), and into the Pentax supplied RAW converter - and pixel peep to work out which has CA adjustment applied

Matt

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Thanks MattMatic for that info. I would be very happy if I found that the in camera settings were being applied automatically when opening the file in PCU - as I have very little experience of working in detail with these type of adjustments, I would be happy to leave it to the camera's algorithams (presumably they work out some correlation to the focal length and aperture used).

I'll take the test shots as you suggested and compare them at high zoom. And of course it would be valuable to start trying it out manually also. Peter Burian in the Magic Lantern Guide discounts the importance of Distortion Correction mainly, stating that modern lenses are now so good, but he says that Chromatic Abberations are a more significant problem. If I get the 14mm wide angle I want though I guess I'll be worrying about distortions a lot more, and if it's an old lense then I'll have to correct in software as the camera functions would not work with that old lense.

Thinking about what people have been saying on white balance - I support the view that even in RAW its a good idea to get as close as you can when shooting. One example is daylight setting compared to AWB, where generally 'daylight' reproduces the greens and blues we see naturally more faithfully. I also have found it is not always easy to achieve the ideal WB in software, with every different converter offering differnt tools and approaches.

I have never found a simple Hue & Temp slider arrangement satisfactory.Other converters try other approaches - has anyone tried Lightzone with its 'colour wheel'? My favourite at the moment is Sagelight 4.2, which offers a sometimes bewildering array of controls, but they often interact, giving you more subtlety and very fine control. For example, in the 'Pro (Auto) Colour Balance' section, you have a 'tint' slider that really combines Hue & Temp, but that is coupled with a 'Strength' and 'Saturation' slider. Setting a higher strength first, then getting the tones and intensity right (it looks overdone), then you just reduce the strengh of the adjustments to the natural level with the strength slider going back down again.

Anyway, thanks for the advice all, much appreciated....

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K7 with BG4 Grip, Samyang 14mm f2.8, DA18-55 WR, 'A' 28mm f2.8, 'K' 75-150 f4.0, Tamron Adaptall 135mm f2.8, AF280T flashgun, Pentax 2X teleconverter, remote control unit

You're right, it's all metadata in addition to the sensor data which doesn't change. AFAIK PEFs can't be changed (at least not by Lightroom/ACR) because the format is closed and owned by Pentax, so development settings have to be stored in sidecar files (.XMP or something I think?). DNG is an open standard published by Adobe, so the various development settings can be written into the actual file, but you also have the option of using a sidecar file if you want to (no idea why, but you can).

Just to make it all as clear as mud, Lightroom doesn't actually write anything into or alongside image files unless you ask it to, because everything is stored in the catalogue database.

Bonus tip: If you "convert to DNG" when importing raw files then you end up with smaller files than either PEF or DNG produced in camera and with no loss of quality - at least, I have found this to be the case with a K100D, K-x and K-5. I believe this is because Lightroom applies a better (and probably more complex) lossless compression algorithm than the camera does.

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Simon

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