A900 Metering compared to a700 and Noise Issues ?

[Greg Beetham]

The problem that I had in mind was what is happening accross the entire surface of the FF sensor in translating the sensor data into an image (light cone transmission taken into account, center to edge using a FF lens) as compared to the A700, with the smaller sensor...using the advantage of a DT lens with it's possibly more even light cone, (center to edge), although just how one would go about testing this, I don't know.
One thing I'd guess you would want is the LV value, (light meter reading, I take it) to register at the same value in both cameras as a basis point, although obtaining that might be easier said than done. ISO6400 is probably a bit extreme to conduct the test with, it's amazing the two are as close as .3 of a stop at that end of the scale, allowing for the afore mentioned shutter, apeture, mechanical/tolerance (and other potential variables), it's interesting that the A900 metered at 2.62 LV (value in exif) but actually exposed .3 stop less than the A700 with LV 2.75 a brighter reading?? it should really have exposed .3 more....shouldn't it? (picking nits)
Greg

[j_p_p]

Check this comparison between the a700 vs a900 (maybe he used JPEGs i don't know) :

http://anandtech.com/digitalcameras/sho ... i=3442&p=5

Once again the a900 is darker (underexposed???) than the a700 (or is it a White Balance issue ?? hum...) , maybe this explains the result (or used JPEG and the a900 JPEGs aren't as good as the a700) ?

Anyway, is seems that this shouldn't be happening because the a900 has actually less pixel density than the a700.

[Greg Beetham]

I am tentatively of the opinion that it's due to the image/sensor manipulation because of the light falloff from center too edge on the FF format, (using a digital sensor).
The only issue is maybe a slight discrepancy with the metered ambient and the exposure based on that value vs the actual result, (after the adjustments are done), and even then, what is involved....1/3rd through 2/3rds f/stop under...even if the above is correct, it's no great biggie really...
Greg

[j_p_p]

http://www.popphoto.com/cameras/5624/so ... -test.html

Whatever the cause is, it's being mentioned in the reviews (cameralabs and now PopPhoto)

"But that also means that it tends to underexpose" . From what they say i believe that's related to using Wide Metering ?

The review itself is very very positive to the a900 , not Obsessed with "high iso" like most reviewers are nowadays.

[j_p_p]

First of all thank you for all your answers and looking into this

Anyway like i said in Dyxum

"Anyway... i returned the a900 (i was under the Trial Period ) due to this "problems" ...
In retrospective.... what you guys said about Light Falloff maybe due to Lens (70-300G the lens i tried the camera with the most, since i also brought it Saturday) ??? / Underexpose (increasing the noise or better said... Making the noise more visible) / Possibility of the sensor being less sensitive and evertything else makes pretty much sense.
Maybe is also some issue regarding Wide Metering (the one i use the most) combined with the Light Falloff of the 70-300 G that causes this. I Don't Know... Maybe the camera really needs better lens ?

This is not a definitive return, i will just wait until the "dust settles", the camera "matures" and a new Firmware appears (i am sure it will and sooner than later ) . I wanted the camera to replace my a700, but i feel that the a900 still needs some minor improvments, and until then ,the price will probably go down .
I just felt somewhat uncomfortable paying a lot of money , not being 101% happy with some shots like i explained, and to dispose of the a700 without getting a camera that performs effortesly better than it in ALL circunstaces.

Till Then, i will continue to enjoy my a700
"

I am sure more tests will come out, and we will get news soon. I am already missing that Viewfinder neverthless

[j_p_p]

Hi , i found thgis review :

http://www.letsgodigital.org/en/camera/ ... age_2.html" onclick="window.open(this.href);return false;

Maybe this might explain why some people included myself, have mentioned that the a900 tends to produce Darker or Underexposed images than the a700 with the same exposure ? (same F stop/Shutter Speed and ISO)
If ISO 3200 equals ISO 2238...hum...

"
ISO sensitivity of the Sony A900
The possibility of setting ISO values as you desire is a surplus value of any camera. Traditional films have a fixed ISO sensitivity, whereas it is possible to influence the camera's sensor in order to create a bigger playground. A camera manufacturer is eager to use these values and show them in the specifications. However, in practice, these values may very well differ from the genuine sensitivity and a deviation of 20% to 25% is not uncommon. The sensor of the Sony DSLR-A900 is also tested in the DIWA lab as for its sensitivity, and the ISO values did not meet the 200-1600 values. Deviations as much as 29% to 36% less sensitive show that Sony is clearly trying hard to control the noise. Even more astounding are the values measured at 3200 and 6400 ISO, where differences of respectively 43% and 57% are found. In other words, ISO 3200 equals ISO 2238.
"


they are however not too critical of the high Iso perfomance :
"
Noise reduction has been controlled well
The noise values on the Sony Alpha 900 do not disappoint us. On the contrary, we were nicely surprised by the Sony Alpha 900 with values that are close to the Canon EOS 1Ds Mark III, for example. This is an achievement Sony can be proud of. If you shoot in RAW and effectively reduce noise, you will obtain a perfect result. Up to and including ISO 800 this should not be a problem at all. At ISO 1600 and higher, noise becomes more visible and a precise exposure is required or more corrections have to be carried out in RAW afterwards. Not bad, in fact an excellent result by the Sony Alpha 900 that stands strongly in this high resolution class. For those who like to keep control over noise in their own hands; it will be a relief to know that the Sony A900 offers the possibility to deactivate the internal noise reduction all together, in RAW that is.
"