On 29/04/2013 22:02, Peter wrote:

Martin Brown wrote

Although I agree with your ranking I also think that the Canon and
Pentax are a tadge overexposed by at least half a stop and has burned
out the sky too much and the Nokia has underexposed by half a stop
retaining too much sky detail at the expense of the rest of the image.

The internal JPEG details and average info content a

Canon S95 uses its own custom Qtables approx
Luminance Q=93 Chroma Q~88. 2.8 bits/pixel

Pentax K5 Q=100 (both) 5.85 bits/pixel

Nokia 808 Q=100 (both) 7.1 bits/pixel

The bits/pixel is for the main image only.

So the information content in the Nokia shot *is* higher - largely
because the sky isn't burnt out and amazingly the adjacent pixels are
more nearly statistically independent. Impressive for such a tiny lens!

Zooming in hard on the TV aerial allows easy judgement of the psf. The
Cannon S95 has applied some pretty brutal unsharp masking and its image
quality might well be improved by toning it down a bit (if possible).

Very interesting analysis - thank you.

I am not concerned about the Canon S95, though there should be no
image sharpening selected. 2.8 bits per pixel is crap though...

The cheaper Canons use custom quantisation tables that are too brutal.
The image quality would be better if they used Q~95 and ~4 bits/pixel.
High end Canons use scaled versions of the canonical Qtables.

It is actually very hard to detect JPEG artefacts in Q 95 images
unless they are designer test pieces intended to break the codec.

The Pentax K5 is entirely at its default settings with no manual
over/under exposure. I shoot at the max jpeg quality setting. Normally
I get great results with it; the only problem is that one needs a
waist pack to carry it! Ground shots I rarely tweak but airborne shots
usually have a lot of haze which I try to remove using various means.

I also have a Pentax K5 it replaces my older istD (that always needed a
systematic bias added to its default exposure in most lighting). I find
the K5 performs very well after I got used to the chunky battery grip.

The Pentax ex camera image is hardly touched by unsharp masking and so
is superficially softer but that gives you the option to do it later.
You can tweak so many settings internally that it can be confusing.

The basic point about the Nokia 808 is that one no longer needs to
carry a pocket camera, which I think is a great step forward, despite
its limitations (mostly iffy autofocus, so one needs to take time on a
shot). The bigger item is replaces rather well (again in reasonable
light conditions) is a £1500 1080P camcorder...

I am honestly astonished by how close to diffraction limited its small
lens is. I wasn't really expecting the answer that I got.

I am amazed quite how well it does in daytime conditions.

--
Regards,
Martin Brown