Chromatic Abberation for RAW Files?

Hello, I'm a new Pentax user (I've introduced myself in the 'Just Joined' section.)

I have a K7, and I wondered if there was any advice on Chromatic Abberation (and lens distortion) correction when using the 18-55 WR zoom. I've read the manual and the Magic Lantern Guide Book, but they don't cover this detail.

I am aware that when these functions are active the processing is carried out in the camera after image capture (because it takes extra time to display the photo on the LCD). So I am assuming that for RAW (I shoot DNG) the data is calculated and written to the file.

What I do not understand is whether the processing is applied automatically at capture (ie: it would be effective and visable with the DNG when opening in any converter program in the default state(I mostly use Sagelight)), or whether it is just data in an unapplied state and therefore needs to be activated using a converter program. As none of my RAW converters have options for activating Chrom Abb or Distortion correction, I guess this could be done in the Pentax Utility Software?
I tried this converter but for general image adjustment I found it somewhat lacking. But if I need it to appy the corrections I'm talking about then I'll have to reinstall it just for this.

Obviously it would be preferable if the corrections were applied in camera and already active on the photos when opened in any converter, but I cannot see any information on this in the manual or guide book.

Any thoughts would be much appreciated!

Many thanks Peter & David

I don't use lightroom, so I may have to reinstall Pentax Utility for these corrections only.

But I am a bit confused - I have not found that the continuous shooting is affected by having the CA and DC active - only that the display of the image is slower. If shooting a burst the camera responds instantly but then takes the extra time to display the final image of the burst.

And if the corrections are not applied in camera (as you said Peter, nothing is processed in RAW), then what is the camera doing that takes this extra time with these functions active? Is it calculating the settings and storing them in the metadata for the file - in which case would

(Continued - Sorry)

in which case would the file open in Pentax Utility with the settings applied from the camera as default - if not, there would be no point in having the camera set for these functions when shooting RAW at all??

But I also understand from what you explained that you can make the corrections in the Utility software anyway - is this the case even if the functions had not been active on the camera when shooting?

I couldn't say what it is that is taking the extra time, except that the image displayed on the rear screen is a JPG image embedded in the RAW file. Maybe some processing is applied to that.

You are right, there is no point having any corrections set in-camera when shooting RAW, but if your camera can shoot RAW+, the plus is an additional JPG image which will have the corrections/adjustments applied.

Any and all corrections can be applied to a RAW file in post-processing, irrespective of whether or not any particular function was selected at the time of the shot. The RAW image is like film, you make the adjustments in development and printing, not in camera.

EG: you could shoot all day in sunlight, yet have the white balance set to something inappropriate for sunny conditions, like cool fluorescent light (6400K) for example (I've done it, once). With RAW images, you can just change the WB to sunny and the images take on the correct colours.

Does the Pentax Utility change the RAW File with CA correction, or do you have to saved the corrected version out to a TIFF or other bitmap format?

I just leave the Camera in Auto WB all the time. I then adjust WB in Lightroom. Daylight, tungsten, Flourescant, etc in the camera are only approximations anyway. Daylight can mean anything from 4000k to 12000k, so setting it 5500k is pointless IMO.

Horses for courses Smeggy. I prefer to fix my WB to daylight most of the time unless I want a warmer look to daylight images, then I set it to flash. Shooting indoors in artificial light, AWB can get it wrong quite often.

My example was just that, an example of how RAW files can be 'saved' later if some settings weren't quite right on the day.

RE: Pentax utility affecting RAW files, I don't think any RAW converter software makes changes to the original image file. Lightroom, for example, uses sidecar files and a database to hold the changes you make to an image. Hence the ability to undo all your changes at a later date if you want/need to.

The real reason as I see it for using a setting like Daylight (which is the one I usually use) is to preserve the changing colour quality of the ambient light. If we use AWB all the time, as the colour of the light changes so the system will try to negate that change.

So, using Daylight, as I like to make best use of interesting natural lighting conditions, helps me to keep those qualities in the pictures. In extremis, a red sunset will stay red without AWB trying to bring is back to a neutral grey.

Incidentally, an even warmer look can be obtained by setting to Cloudy, which is not so far off the effect of using an 81A filter on colour film.

When we did use film, the colour balance was set for a particular film, so setting to a fixed setting is rather closer to that. Finally, don't forget, if you really want to have a setting fixed, to switch off the camera function that varies the fixed setting over a small range.

I did read on one of the reviews that the K-5 AWB was very accurate
in normal light, not sure about the K-7.

Be careful under trees, the green light gets misinterpreted as
fluorescent

I don't use sidecar files in Lightroom. I just store it all in the database. I'd forgotten about them to be honest. Although I cant see why these develop details can't be embedded in the same RAW file as an extension. JPGs, MP3s and all kinds of other files allow this, but anyway ...

So I'm assuming that saving CA removal settings in the Pentax utility creates a side car file, which other editors like Lightroom can interpret?

Sorry, I don't know the answer to that. I only use Lightroom because to me, it's about the most complete Raw Converter there is right now. I use it for 99.999% of my finished product, and I very rarely use Photoshop or any other digital wizardry.

I do have a trial update from Topaz Labs for their photoFXLab software and I'm going to experiment with that for a while. They are hoping to have fixed the 'missing EXIF' problem.

Exactly right John. AWB is good at times, but I believe that using a fixed colour temperature is better.

EG: If you were to use AWB at a gig where numerous coloured lights are often used, AWB would have a hard/impossible job interpreting the changing scene correctly.

Just worth adding this point:

When shooting RAW, it is only the embedded JPG image that is processed. As mentioned the RAW is just that.

It can be useful to know this - you can use in-camera options (like processing style, lens correction etc) and have that applied to the embedded JPG. There are a few free tools that will extract this JPG from the innards of the RAW file

But it can be equally frustrating, as sometimes the camera can get it more "right" than the RAW processing tool does! Many RAW processing tools will show this embedded JPG first, before handling its own internal RAW processing - e.g. Google Picasa. It's good to have a camera 'reference' that can be called on though - even if you haven't shot RAW+JPG

Also, as stated, Lightroom 4.1 has utterly astounding CA corrections! For example, the DA*16-50 can show some serious axial (longitudinal) CA when shooting wider than f/4 (so you get purple fringe near focus and green fringe far focus) - LR4.1 can completely resolve these issues! Other bright lenses can pop up purple fringing at wide apertures too (e.g. FA50/1.4, etc) Transverse (lateral) CA can be fixed in camera, and is common on the corners of very wide angle lenses - showing itself often as blue/yellow fringing either side of highlighted edges.

Given that LR4 is now greatly reduced in price (LR3 was around £225, LR4 is now around £91 new) it's definitely worth considering

Matt