Some info on the 24 MP Nikon - from a Sony engineer

Started Oct 29, 2008 | Discussions thread
FrankG Senior Member • Posts: 2,226
Re: expensive strategy

Even at base ISO?

It's tricky to judge at base ISO, since the available sensor DR of
decent camera so far exceeds the DR of most available output media,
that they all end up looking much the same, even if the measure
differently. I haven't done any measurements, but I get the
impression (from such things as the DPR DR test, for instance) that
the A900 has quite good low ISO read noise, and therefore quite
extended low iSO DR.

So you are basically supporting my point which is that for all intents and purposes at base ISO (at least) "High Density" cameras such as the new Sony A900 can easily stand up to 100% scrutiny.

No-one said anything about downsizing the output. We invariably
upsize it, since no-one's keen looking at images 24x36 mm.

?
Who said anything about viewing or printing at 24x36mm?

When referring to "downsizing" I am of course talking with reference to comparison to 100% view. Effectively if you print both 12 and 24Mipix image at, say, 19x13 you have effectively downsized the 24Mpix image with reference to 100% significantly more than the 12Mpix image.

The issue is, what do you lose by increasing pixel density? The answer is
nothing (except file size and processor capacity).

Purchase cost!

If you choose to
make an image to your prefences with a low and high pixel density
camera with the same size and tech sensor, the noise will be of the
same amplitude, so you haven't lest anything. What you've gained is
the ability to make larger prints with some detail should you choose.

That is true for very Low ISO range pictures. In fact we ought to be able to do prints of double the size from 24Mpix - but it is a case of how big do we need to go when we can already get large prints of extremely high quality from 12Mpix?
...

However as for the A900 being only "one third of a stop" worse noise
than the D700 "at equal output sizes" - would you mind pointing to
your evidence for that?

First look at Emil Martinec's tables
( http://theory.uchicago.edu/~ejm/pix/20d/posts/tests/D300_40D_tests/ )

  • the D300 has to stand in for the A900, and adjust for area. This

might not be completely accurate, but since sensor efficiency seems
to go across sensor families (look at the Canon ones) it's a fair
assumption. Now look at Clarkvision

( http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary/index.html ) again letting the D300 stand in for the A900. On the sensor efficiency side (from Emil), we find that the D3(or D700) has about 1/3 stop advantage in area efficiency. Since the sensors are the same size, that translates to overall efficiency. Now look at the read noise figures (from Roger) and we find an advantage (more than a stop) to the A900 at low ISO's, with them being about even at high ISO's. This suggests that if anything the A900 will have a slight advantage at low ISO's. this actually triangulates with real test results, where the A900 seems to have a measurable DR advantage over the D3/D700.
It's a bit more difficult to find noise tests in raw at high iSOs
(and JPEG tests tell you nothing about the sensor qualities) but this
thread here:

http://forums.dpreview.com/forums/readflat.asp?forum=1037&thread=29804929 did an equal size comparison in RAW at 3200 and I'd agree with his conclusion, the A900 holds up quite well, certainly seems to triangulate with my (around 1/3 stop) estimate. Above 3200 we'd expect the D3/D700 to pull further ahead, since its sensor efficiency advantage is still there and relative read noise is dropping. Beware of basing you assessment on JPEGs, the A900 seems to have a very poor JFIF engine. That may affect your purchase decisions, but doesn't tell you much abour relative sensor efficiency.

Not at all sure about your reasoning here and I'm afraid I don't believe your estimate of "around 1/3 stop" advantage for the D700. There seem to me to be several less than obvious theoretical complications which quite probably at least throw your estimates off beam (and I can't say I have confidence in your assumptions along the way).

Also there is the problem that your opinion seem to be a long way out of step with results and comparisons posted elsewhere including, notably, DPReview's own review of the Sony A900. Check for example this page of the review:
http://www.dpreview.com/reviews/sonydslra900/page20.asp
I quote:

"Measured noise as you move up the ISO range is broadly the same for all cameras, though one glance at the crops above should be enough to tell you that Sony is making increasingly desperate attempts to control noise through pretty brutal noise reduction as you head up the scale. By ISO 3200 the result is a blurry mess with little fine detail - with the added insult of visible chroma noise in the shadow areas. I think it's fair to say that ISO 3200 and 6400 are firmly in the 'emergency use only' bracket (of course with 24MP to play with you shouldn't have many problems at small print sizes).

That's a long way from your third of a stop estimate.

  • Frank

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