More on lens "correction"

In many cases, the "corrective" features of a manufacturers software will work very well. They aren't the complete answer, and anyone who has used an ultra-wide lens will know that it has its own unique character, and you won't get the same result as a tilt/shift lens without a lot of work.

However, if you are interested in what is actually happening to a file and exactly what kinds of correction are being employed, then its useful to download yourself a copy of a dcraw programme (they are open source and usually free, though a donation always helps them develop) and see what a "raw" raw file looks like. Apart from anything else its the closest you can get to seeing what the sensor is actually recording, without any "interference" from the manufacturers software.

This is not something that I would recommend as a matter of course, and you may try it and decide that it's much easier to stick with the native software or ACR etc. The point that I am trying to make here, is that when you do use a dcraw programme, you are then in a much better position to decide if how the software processes the file "improves" it and whether it corrects it in way that works that you. I think it doesn't do much, Others think it does.

I spend my life taking photographs, and editing them. I'm also constantly testing and seeing what does what. Its my job, and I allocate time for that. If you haven't got that time, would prefer to use it doing something else, or quite simply don't care that much, then you won't be missing much. I invest a lot of time in photographing architecture, because it partly pays my mortgage, and wide angles are an important part of that, so I'm keen to know what they are doing and its of interest to me to see if I can get a more useful file out of a software programme that doesn't "correct" a file in the way that the manufacturer of the camera and lens thinks it should be "corrected"

In some cases I can get a better result from dcraw and the photoshop transform tools, in some cases I can't and in some cases it doesn't matter. It all depends on what I want to do and what kind of image I'm working with and, most importantly, to what use its going to be put to.

If you haven't read it already the Dpreview article which has the heading "What if I don't want to use the manufacturer's RAW converter?" at http://www.dpreview.com/...a-distorted-view-in-camera-distortion-correction/2 is an excellent (short!) read, and gives a nice overview of the issue. There's also a companion piece to this at:- http://www.dpreview.com/articles/5653763779/a-distorted-view-in-camera-distortion-correction/1

Perhaps it might be useful to end with an example and some process, to illustrate what I mean.

 
 Panasonic GH2 7-14mm lens. Tripod. 1/10th. sec. f/11 ISO 160 

The top picture is a jpg.("corrected") straight out of the camera. For the bottom one, I processed it in Rawker (dcraw) and produced a 16-bit tiff which I opened in Photoshop. I then edited the file, using the transform tools. You will notice that in the bottom right there is more of the sofa visible. dcraw does give you this "extra" bit which is very helpful for the transform process.

Not perfect, but the client was happy, and it shows what an alternative can give.