Olympus UK E-System User Group

Olympus UK E-System User Group (http://e-group.uk.net/forum/index.php)
-   Lens focus (http://e-group.uk.net/forum/forumdisplay.php?f=15)
-   -   Lens Corrections? (http://e-group.uk.net/forum/showthread.php?t=47230)

snerkler 18th February 2018 08:59 AM

Lens Corrections?
 
I've been trying to find out exactly what lens corrections are automatically applied to Olympus RAW files but can't find anything conclusive and was wondering if anyone here knows? General consensus suggests that geometric corrections such as barrel distortion are but chromatic aberrations aren't, is this correct?

Otto 18th February 2018 10:10 AM

Re: Lens Corrections?
 
I can only say that judging by DxO's rendition of the unprocessed RAW image no geometric corrections are applied. Shots taken with the 12-50 at 12mm show very obvious barrel distortion!

snerkler 18th February 2018 12:23 PM

Re: Lens Corrections?
 
Quote:

Originally Posted by Otto (Post 440144)
I can only say that judging by DxO's rendition of the unprocessed RAW image no geometric corrections are applied. Shots taken with the 12-50 at 12mm show very obvious barrel distortion!

So is it software such as lightroom that read and automatically enable embedded corrections then?

Greytop 18th February 2018 12:29 PM

Re: Lens Corrections?
 
Quote:

Originally Posted by snerkler (Post 440168)
So is it software such as lightroom that read and automatically enable embedded corrections then?

I would suspect so, I don't use Lightroom but Capture One Pro certainly automatically corrects for distortion and CA.
Within CO you can opt turn off the corrections.

snerkler 18th February 2018 01:16 PM

Re: Lens Corrections?
 
Quote:

Originally Posted by Greytop (Post 440170)
I would suspect so, I don't use Lightroom but Capture One Pro certainly automatically corrects for distortion and CA.
Within CO you can opt turn off the corrections.

Thanks for your help. LR Ďappearsí to add corrections as it says so, but without seeing unaltered RAWs I cant say what and by how much. CAís donít seem to be corrected though as you can manually select to remove CA which does remove some fringing. Whether the Olympus file removes some and then LR removes more I donít know :confused:

Otto 18th February 2018 03:15 PM

Re: Lens Corrections?
 
DxO uses its own lens corrections base on measurements on each body/lens combination. It removes distortion, fringing and CA very effectively.

pdk42 18th February 2018 04:21 PM

Re: Lens Corrections?
 
This is the situation...

- The m43 standard includes a provision for lenses to pass geometric distortion correction data to the camera. The camera can use that to correct JPEGs

- All cameras AFAIK, also pass that data as EXIF into raw files.

- Many raw converters use this EXIF data to automatically correct images. It often can't be turned off ( e.g. Lightroom).

- Some converters ignore the correction data (e.g. dcraw).

- Some converters supply their own correction data (e.g. DxO).

- CA correction by the camera used to be vendor specific but I think these days that is applied universally (at least across Olympus and Panasonic cameras and lenses).

- CA correction by a raw converter is usually automatic based on analysis of the image. It doesn't need EXIF data (so it will still work with legacy lenses for instance).

PeterBirder 18th February 2018 04:23 PM

Re: Lens Corrections?
 
Quote:

Originally Posted by snerkler (Post 440179)
Thanks for your help. LR Ďappearsí to add corrections as it says so, but without seeing unaltered RAWs I cant say what and by how much. CAís donít seem to be corrected though as you can manually select to remove CA which does remove some fringing. Whether the Olympus file removes some and then LR removes more I donít know :confused:

You cannot ever view a raw file (raw not RAW files as wraw is not an acronym, it literally means the raw data from the sensor) or apply any type of correction to it, it has to be "developed" or decoded into a form such as JPEG which can be displayed first.

Software such as Lightroon, Olympus Viewer 3, Capture One Pro or DxO apply lens corrections (and other corrections) at a late stage of the conversion process. Like Otto I use Dxo and that has the ability to show before and after correction images either by switching between before and after views or by displaying both side by side. As Otto says the default corrections applied (which also includes things like lens softness) are the result of considerable testing of sample camera/lens combinations but you can also manually adjust these further if you wish. I'm not sure how comprehensive the corrections applied by default in Lightroom are but I believe you can also import lens profiles from third parties or devise your own.

On the other hand if the camera is set to record JPEG only, the camera firmware will, I believe automatically apply lens correction data to the JPEG's it produces. As a matter of interest Olympus Viewer 3 is effectively the same as the camera firmware processor and you can make your own changes to it as well.

Hope this helps.

pdk42 18th February 2018 04:38 PM

Re: Lens Corrections?
 
Quote:

Originally Posted by PeterBirder (Post 440208)
You cannot ever view a raw file (raw not RAW files as wraw is not an acronym, it literally means the raw data from the sensor) or apply any type of correction to it, it has to be "developed" or decoded into a form such as JPEG which can be displayed first.

I know why you say this Peter, but it's not quite as simple as that. Any file portending to represent image data has to be processed to be viewed. Even a BMP file, which is probably the nearest to a pixel map as you'll find, has all sorts of meta data and formatting in it. JPEG files are complex structures that have varying levels of compression and fancy encoding in them and need to be read by special programs to turn them into an image on a screen or printer.

In that sense then raw files are just another format and need to be interpreted to be displayed. Recent versions of Mac OS actually have raw file decoding in the OS so no additional software is needed.

The key difference between raw and JPEG of course is that the raw data has has a lot less processing done to it in camera. In particular, there is no WB, sharpening, tone curve, NR, shadow/highlight processing, vignette correction, CA correction, geometric distortion correction etc etc. That's the huge benefit of raw of course since all this can be done later on the PC. No amount of post processing can easily undo sharpening halos for example.

Note though that raw files are invariably pre processed to some degree - it's not just "raw data of the sensor". Fuji bake NR in, Sony do data hidden compression (e.g. the famous " star eater " bug), Olympus can add corrections without you realising (e.g. "shading correction" finds its way into raw files unless you turn it off).


All times are GMT. The time now is 04:29 AM.


© The Write Technology Ltd, 2007-2019, All rights reservedAd Management plugin by RedTyger