“AS” or Manual priority

November 30th, 2010

I am not the general manual mode shooter. I prefer A or S mode, but sometimes you need to control both: You may want to get some motion blur that requires 1/30s exposure, but you need f/5.6 to get the depth of field to just make the background recognizable without becoming too sharp for your blurred subject.

Wait for the right light … or use Auto-ISO:

When you switch the ISO settings of the D90 (didn’t try with other DSLRs) to Automatic, the camera will choose the ISO that will fit the speed and aperture chosen in manual mode! How cool is that! The metering is like in all other modes, even AE-L works. As long as the ISO range you configured will allow for a proper exposure the exposure meter in the viewfinder will show no under/over exposure. For Hi- and Low-key shots you can dial in exposure correction and the exposure meter will account for that. When framing you can remind  yourself of the exposure compensation by pressing the +/- button to display the compensation in the viewfinder.

This is not so awfully useful, most of the time you can achieve the same in S or A mode, but it is a nifty little feature your D90 has in its chips.

For some reason this doesn’t work anymore when you mount a flash, not even when it is set to manual.

Expose digitally

November 5th, 2010

The most important difference between film and digital shooting is exposure. If there is any other.

For film you exposed for the luminance of the tonal range that was of main interest and you where good. The natural gamma of film (the gamma notion came from film material and had been only adapted to digital via the TV encoding) put this range in the steepest (or flattest - depends on how you want to view it) part of the sensitivity curve of the film material - highlight got smoothly clipped. The rest was lab work and even the simplest services performed the required corrections without asking any questions.

When you shoot JPEG the camera imitates the same thing, but when you want to get beyond that and shoot RAW things get more complicated.

One thing is the white-balance (WB). Either you choose or the camera does, but this will effect the process above and it is hard to correct afterwards. When you shoot RAW and control the exposure with the histograms - you have to control each channel of the RGB - the histograms are adjusted by the WB that had been active during the shot. This can lead to “burned” highlights when correcting the WB: In the histogram you have seen on the display the BLUE channel looked OK, but the correct WB requires a hight blue level and blow out becomes visible. There is a way to prevent his, it is called UniWB, but still the questions remains what you are exposing for.

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