D4 vs 1Dx (Imaging Resource), RAW, ACR, 6400-12800

Started Sep 4, 2012 | Discussions thread
Andre Affleck Senior Member • Posts: 2,362
Re: D4 vs 1Dx (Imaging Resource), RAW, ACR, 6400-12800

Lance B wrote:

bobn2 wrote:

Lance B wrote:

bobn2 wrote:

Yes, but it yields a silly result - one where a camera can appear better in low light simply by gaming the meter to give more exposure at some set ISO. that really doesn't help, because if you need 1/30 sec, say, you'll raise the ISO till you get it, even if that results in a different setting on different cameras, so this really isn't a good tets of low light capability.

That is not what I am saying. Gees, you like to argue against a point I am not making.

I'm arguing against a point you used to be making. Your point seems to be abit flexible, as you discover that you hadn't thought it through.

So, if the ISO's of the tested camera's are slightly different and/or one or both is inaccurate, as I have been saying, then the testers will need to adjust one or the other's shutter/aperture combo to get similar looking test photographs.

No, this is the completely the wrong way to perform the test. I don't think you have fully digested what bobn2 has been trying to say.

Many have trouble with this topic since it is a shift in paradigm from what they are used to - film exposure , which uses a different mindset.

In digital capture what counts "sensor exposure" since this determines how many photons are captured. It is the light gathering capability of the camera (total number of photons captured) which dictates how well the camera will performance with respect to noise, DR, S/N, etc. The *only* thing that determines sensor exposure is sensor size, aperture and shutter speed.

So, the only way for the test to be fair, you must give each camera the same number of photons to play with. Only after they receive the same number of photons can you judge how well they can process those photons.

If the camera's ISOs are "inaccurate", then you pick an ISO (it can be arbitrary really), and set both to the same shutter speed and aperture (equal number of photons). If the images are rendered at different brightnesses, you make them equal using your converter's EC slider. This essentially equates the differences in analog "ISOs".

Also understand that with most modern cameras (especially those with Sony sensors) pushing high ISOs digitally is nearly identical to doing it with analog amplification. So whether you push shadows in post, or push them with "ISO" you will get the same result (for high ISOs above 1600). This is why the above technique works best.

For ISO above 1600, the D4 and the D800 could essentially be ISO-less. IOW, you could leave your camera at ISO1600 and shoot underexposed as far as you want and then "choose" the ISO after the fact in your raw converter. Your underexposed ISO1600 shot pushed 4 stops would look no different than ISO25,600. You can see how ISO is really meaningless in the this context since it really doesn't matter what the camera's ISO is.

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