Sony Alpha DSLR-A700 Review
Here you can see a generated GretagMacbeth ColorChecker chart, place your mouse over any of the labels below it to see the color reproduction in that mode. Select a camera/setting combination from the 'Compared to' drop-down to comparative boxes inside each patch.
The A700 delivers a very similar color response to the Canon EOS 40D except for its rendition of the blue patches which have less red in them (hence the very slight purple tinge to the 40D patches). As you can see the A700's huge number of preset image 'Creative Styles' do provide a wide range of canned color and tone responses.
|Sony DSLR-A700||Compare to:|
Artificial light White Balance
I'm truly beginning to wonder if I'll ever be able to say anything good about automatic white balance in artificial light for digital SLRs. With each new model we see no real improvement and in some cases the camera's "best guess" is way off the mark, as you can see from the results below. Even the preset WB options on the A700 don't do a particularly good job at hitting the right color temperature.
|Incandescent - Auto WB
Red: 16.2%, Blue: -24.9%, Very Poor
|Incandescent - Incandescent preset WB
Red: 4.3%, Blue: -8.6%, Average
|Fluorescent - Auto WB
Red: 13.4%, Blue: -23.2%, Poor
|Fluorescent - Fluorescent preset WB
Red: 5.8%, Blue: -9.6%, Average
Long Exposure noise reduction / Night shots
Our usual 30 second exposure test produced no hot pixels from the A700, so the optional long exposure noise reduction option (dark frame subtraction using an equal exposure with the shutter closed) made no difference here.
|Noise reduction Off||Noise reduction On|
|ISO 100, 30 sec, F20||ISO 100, 30 sec, F20|
The A700's built-in flash unit performed well delivering correctly exposed images (it even nailed middle-gray on our color patches tests shot) without any hint of color cast or white balance problems. With a human subject skin tones were natural and again well exposed.
Overall Image Quality / Specifics
It would be fair to say that as a baseline (at lower sensitivities) the A700 delivers very good images which demonstrate good resolution a 'standard' tone curve and natural color. My primary concern about image quality was the way in which Sony have implemented higher sensitivity noise reduction on the sensor. This implementation appears to produce two issues; firstly it's not possible to turn off this noise reduction or reduce it to a level where it does not interfere with image quality. Secondly that because it can't be turned off and that it occurs so early in the image pipeline that RAW images always have some amount of noise reduction applied to them; this is very obvious when converting higher sensitivity RAW files. Frankly I was pretty surprised to discover this and would have expected Sony to realize that most photographers expect RAW image files to contain exactly that; a 'raw' representation of the data from the sensor (one measurement per photosite) with no image processing, enabling them to process the image as they like with as much or as little noise reduction as they prefer.
Other noteworthy observations are the differences in dynamic range between ISO 100 and 200, with ISO 200 actually being 'base sensitivity' for the sensor but without any indication that this is actually the case on the camera (or clearly in the user manual), virtually useless automatic white balance in artificial light (although to be fair this is no different than most other digital SLRs today) and no difference in tonal balance using DRO Standard or DRO Advanced Auto options (although manual settings do work).
When ISO 100 isn't really ISO 100
So we've already established that there's a dynamic range difference between ISO 100 and 200 and that the sensor's base sensitivity is actually ISO 200 (although this isn't indicated on the camera). What this means in reality is that in ISO 100 mode the camera is effectively over-exposing and relying on the headroom available from the sensor to 'pull down' to a normal response. This can be seen clearly if you shoot RAW+JPEG at ISO 100 and process using a third party converter such as Adobe Camera RAW. The ISO 100 RAW image appears over-exposed and requires approximately -1.0 EV digital exposure compensation to achieve normal tone (note that ISO 200 RAW also required a -0.3 EV digital exposure compensation).
|ISO 100 JPEG, 1/30 sec, F8||ISO 200 JPEG, 1/60 sec, F8|
|ISO 100 RAW, 1/30 sec, F8||ISO 200 RAW, 1/60 sec, F8|
|ISO 100 (as above but with -1.0 EV digital comp.)||ISO 200 (as above but with -0.3 EV digital comp.)|
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