Increasing sensitivity to light: in camera or in post?

The Phase One P65+ and the new New IQ180 80 MP camera backs can go from a top ISO of 800 to up to 3200 by dropping the effective pixel count of the image to 15 and 20 MP respectively. This makes sense as the new "pixels" are 4 times as large. Still, one can reduce the size of an image in Photoshop or any other processing software. So what are the differences in the resultant image. Any experience or ideas?

Asher

No experience on this subject, but here's why I think it works:

In the camera, they can take the 4 pixels and add them together, and then apply the gain.

In Photoshop when you reduce the size of the image, I don't think any of the available operators does exactly that. In fact, if you start with a 20 x 20 pixel image and put some brush strokes on it, and then re-sample it down to 10 x 10, I'm pretty sure they don't, but it's a little hard to tell.

Hi, Asher,

Asher Kelman said:

The Phase One P65+ and the new New IQ180 80 MP camera backs can go from a top ISO of 800 to up to 3200 by dropping the effective pixel count of the image to 15 and 20 MP respectively. This makes sense as the new "pixels" are 4 times as large. Still, one can reduce the size of an image in Photoshop or any other processing software. So what are the differences in the resultant image. Any experience or ideas?

Click to expand...

Well, simplistically, larger sensels improve the noise performance for any given photometric exposure on the sensor. Note that this happens before demosaicing. (It is important to recognize that in the normal processing, there is one pixel per sensel, but they are not the same thing.)

Combining developed pixels will improve the noise performance too (compared to the noise performance for the individual, small pixels).

There may well be matters that I'm not right now aware of (since I don't work much contemplating this matter) that would make the two not theoretically equivalent (likely involved with the matter of demosaicing plus the matter of the nonlinear representation of R, G, and B).


And of course there could be "practical" reasons that would make the theoretical picture not predict actual results.

I know that's a complicated way of saying "I have no idea"! But we work with what we have at any given instant.

Best regards,

Doug

Doug Kerr said:

Combining developed pixels will improve the noise performance too (compared to the noise performance for the individual, small pixels).

Click to expand...

....... and if so, what are the preferential orders of processing in order to maximize noise free images when employing image size reduction for that purpose.

Are there any unique qualities of various RAW processors which would suggest any required steps prior to or after reduction in size should be done in one particular program versus another?

I know I've already asked a lot of you! Still, film exists in large sheets and 8x10 cameras are relatively inexpensive. Since I am fitted with 120 mm, 240mm and 300 mm lenses, I'm in the position to use film for the same purpose: have more resolution than one needs and down-sample.

Let's consider that w'ed need an ISO of 3200 to be as noise free as an image on a 5DII at ISO 800.

Also include the idea of taking the same picture with 8x10 film and reducing the size of the scanned image to get an even better noise free final image. Of course, the film would be color and the choice would be Kodak Portra NC 400. So it is very limited! Under-exposed but pushed, the highlights are fine but the shadows will not be so well recorded.

Thanks so much,

Asher

Here's one method I have tried with some success.

Convert the image to Lab mode.
Select the L channel
Despeckle
Gaussian Blur
Reduce resolution

Bob Rogers said:

Here's one method I have tried with some success.

Convert the image to Lab mode.
Select the L channel
Despeckle
Gaussian Blur
Reduce resolution

Click to expand...

Bob,

I'd imagine that the Topaz. Neat Image and other noise reduction software plugins might also work in Lab mode. What I'm wondering is how this compares to in camera binning.

Asher

Hi Asher,

If you buy me one of those cameras I'll try it out and get back to you!!!

;-)

Bob Rogers said:

Hi Asher,

If you buy me one of those cameras I'll try it out and get back to you!!!

;-)

Click to expand...

It's like, "Walk a mile in someone else's shoes!" Then one is 1 mile away and one has their shoes. Same with a camera!

Asher