Alpha 700 ACR 4.2 quality revealed

THE ALPHA 700 cameras tried in Italy by press representatives, including Paul Olsen of Dinside Data in Norway who sent us the raw and JPEG files for the image used here, may or may not have been pre-production samples. Some cameras which were felt to be poor had over 1,000 exposures recorded before the event. Olsen’s camera appears to have been new, recording frame counts in the 40s during his shoot, and may be a final production sample rather than one of the much-used demo bodies.

Now that Adobe Camera 4.2 has been been released with support for the Alpha 700 RAW and cRAW file formats, it is possible to dig into one of Paul’s shots and see how it compares with the JPEG.

Here is a small version of the in-camera JPEG – an impossible exposure, and not tested using DRO on this occasion:

The exposure is actually pretty well balanced, just allowing white to clip and revealing some shadow detail.

Here is a close-up section of the image, at 100 per cent:

Now let’s compare this with a default auto conversion by Adobe Camera Raw. Sharpness 25, radius 1, auto brightness and contrast (the exposure remains at zero, the auto adjustments only affect other parameters):

We are immediately able to see that the palm trees have gained a great deal of detail and the shutter under the letter R of ‘Ristorante’ has slats instead of moiré.

It is possible to boost detail extraction to 100 and alter the exposure – to -0.95 with +24 Highlight Recovery:

You can now see artefacts as well as extra sharp fine detail, but the painted stucco wall behind the sign letters appears now to have some texture. This is an extreme treatment (Sharpness 50, Radius 0.5, Detail extraction 100) and in some ways it does more harm than good. It is telling us that with the kit 16-105mm lens, some fine spatial frequencies at low contrast are being resolved. Contrary to the easy opinion to express, green shutters do not mean extra sensor resolution because there are twice the number of green sensels. Green sensels actually detect contrast differences most in magenta coloured objects – it’s the red sensels, mainly, which provide detail contrast in green coloured objects. If you doubt my knowledge in this respect, get a deep red and a deep blue filter gel and try looking at a red cross flag through the red filter, then through the blue, and see which one shows you the cross! A cornflake box makes a good study target. You’ll soon see why more green sensels actually means more sharpness in orange-magenta-red coloured targets.

And those shutters are barely green, they are so close to neutral that they make a very good unbiased high resolution target. And… they are just a little bit off being horizontal lines. This really taxes the sensor. Diagonals, easy if a bit jaggy; true verticals and horizontals, easy but sometimes spurious artefact resolutions emerge. Just a bit off horizontal or vertical, that’s genuinely revealing what the sensor can do. I reckon it is doing pretty well.

To see what could be done with ACR controls and the new .ARW file in terms of dynamic range and lack of noise, I adjusted the file using -1.25 exposure plus Fill light at 50 and Brightness at 50:

Here is a close up section from the opened-up shadow detail:

It has been suggested, despite the 18MB size of the new .ARW files, that the Alpha 700 only uses 12-bit conversion. If it does, it is the best 12-bit conversion around. Workable detail has been recovered from a dark area of an image here after first REDUCING exposure in the main ACR control by one and a quarter stops to pull in the highlights. Compare this with what happens if you mess around with Levels on the in-camera JPEG to try to pull detail from the same dark area:

When I have a production model A700 myself, I’ll be able to make better comparisons. What can be said is that raw conversion reveals a camera very different from the story told by the JPEG. Since I do not know the characteristics of the 16-105mm lens – this can only be judged by using alongside several other lenses in many situations – it is not possible to say whether this represents the finest detail the camera is capable of. It is already comparable to the Nikon D2X and well up to Alamy (48-50MB file size export) standards.

– David Kilpatrick