Image parameters

The *ist D provides three levels of adjustment (-1, 0, +1) to the three image parameters of contrast, sharpness and saturation. While it's good to see Pentax providing parameter adjustment (and to be honest it's certainly expected on any digital SLR) it's a pity they didn't provide more latitude of adjustment and possibly in finer steps, perhaps -3 to +3.

Contrast adjustment

Adjusting the contrast setting alters the shape of the 'S curve' used to map the linear image data captured by the sensor into the selected gamma (sRGB / Adobe RGB). A lower contrast setting maintains more of the original data's dynamic range but leads to a flatter looking image. A higher contrast setting stretches the grayscale (dark to light) of the image and could lead to clipping of both shadow detail and highlights. Interestingly the *ist D appears to make the majority of its contrast adjustment at the bottom end of the grayscale (blacks), thus mostly affecting shadow detail.

Settings: ISO 200, FA 50 mm F1.4 @ F14 (Studio Strobe), Small/

	Contrast	Luminosity histogram
-1
0
+1

Sharpness adjustment

One of my niggles with the *ist D are soft images, I personally feel that this is a sharpening issue, that the sharpness is there in the image data but that the camera's internal sharpening algorithms aren't set strong enough. As you can see the +1 setting below delivers a fairly sharp image but I personally think this should be the default (0) and there should be at least one more sharpness setting above this.

Settings: ISO 200, FA 50 mm F1.4 @ F14 (Studio Strobe), Large/

	Sharpness (200% crop)
-1
0
+1

Color Saturation adjustment

One thing which struck me about *ist D images was their natural color balance and sensibly selected color saturation (not under-saturated and not Disney color). The color saturation adjustment allows you to shift to the other extremes if you so desire, for instance the +1 setting could be useful for landscapes on a cloudy day.

Settings: ISO 200, FA 50 mm F1.4 @ F14 (Studio Strobe), Small/

	Color Saturation	100% crop
-1
0
+1