Pixel Density Question

[DBY]

Sorry to bring this debate up again and I promise that I researched this extensively beforehand
I am trying to understand the RAW/JPEG influence on sharpness and have questions on pixel density. I think I have figured this out but need someone to check my thinking. For a point of reference I am looking at a Nikon D700 which has a nominally 12mp sensor. The D700 has three Image Size settings: Large, Medium and Small, and from the manual, the settings result in a pixel count of 4.3k x 2.8k = 12mp, 3.2k x 2.1k = 6.8mp and 2.1k x 1.4k = 3.0mp respectively. My first question is how does the camera accomplish this change in pixel count? It doesn’t appear to me that the camera is using fewer sensor pixels with each setting, and it is still a full frame image with the same nominal image dimensions. When I pixel peep, I can see the pixel rendering degrades going from Large to Medium to Small settings (i.e. with reductions in Image Size, there are fewer rendering pixels attempting to render the same image size, so the rendering pixels are larger with reductions in Image Size). My theory, which I am seeking clarity on, is that the reduced pixel “count” of the Medium and Small settings are not based in a difference of sensor pixels used, but is actually accomplished by a processing algorithm in the camera that attempts to render the original 12mp picture with half the number of rendering pixels at each setting. Is this how it works?

Second question is on sharpness of RAW versus JPEG. I know the raw file doesn’t change in size regardless of the Image Size setting. Since Large Image Size is 12mp, and I have attempted to pixel peep the raw file to be certain, but it seems that the effective pixel density is the same for the JPEG Large setting and the RAW image. Is this generally true? If so, then am I correct to conclude that what is considered to be the enhanced acuity characteristics of RAW over JPEG doesn’t come from a different pixel count but actually comes from the higher image capture bit count (12 or 14 bits in the case of the D700) over the 8 bits of JPEG, the lack of JPEG compression algorithm in the RAW file and possibly other processing subtleties. Not trying to start a RAW versus JPEG battle – the engineer in me just needs to know how this works.

 

[greybeard]

You may find the answer to your questions here:

New Camera and Photography Articles, Nikon DSLR camera and lens

mirrorless, DSLR, and compact camera and photography articles, by Thom Hogan

bythom.com

 

[Ysarex]

Sorry to bring this debate up again and I promise that I researched this extensively beforehand
I am trying to understand the RAW/JPEG influence on sharpness and have questions on pixel density. I think I have figured this out but need someone to check my thinking. For a point of reference I am looking at a Nikon D700 which has a nominally 12mp sensor. The D700 has three Image Size settings: Large, Medium and Small, and from the manual, the settings result in a pixel count of 4.3k x 2.8k = 12mp, 3.2k x 2.1k = 6.8mp and 2.1k x 1.4k = 3.0mp respectively. My first question is how does the camera accomplish this change in pixel count? It doesn’t appear to me that the camera is using fewer sensor pixels with each setting, and it is still a full frame image with the same nominal image dimensions. When I pixel peep, I can see the pixel rendering degrades going from Large to Medium to Small settings (i.e. with reductions in Image Size, there are fewer rendering pixels attempting to render the same image size, so the rendering pixels are larger with reductions in Image Size). My theory, which I am seeking clarity on, is that the reduced pixel “count” of the Medium and Small settings are not based in a difference of sensor pixels used, but is actually accomplished by a processing algorithm in the camera that attempts to render the original 12mp picture with half the number of rendering pixels at each setting. Is this how it works?

I'd say yes. I don't have a D700 but it should be easy enough to test. Set the camera to save raw + JPEG and set the size to medium. Take a photo and examine the raw file -- 12mp? Then the JPEG was resized in processing to create the medium output file.

Second question is on sharpness of RAW versus JPEG. I know the raw file doesn’t change in size regardless of the Image Size setting.

You just answered the question above.

Since Large Image Size is 12mp, and I have attempted to pixel peep the raw file to be certain, but it seems that the effective pixel density is the same for the JPEG Large setting and the RAW image. Is this generally true?

Yes.

If so, then am I correct to conclude that what is considered to be the enhanced acuity characteristics of RAW over JPEG doesn’t come from a different pixel count but actually comes from the higher image capture bit count (12 or 14 bits in the case of the D700) over the 8 bits of JPEG,

No.

the lack of JPEG compression algorithm in the RAW file and possibly other processing subtleties.

It's the other processing subtleties. The camera processor sharpens the image when creating the JPEG. In processing a raw file I have a choice of multiple different ways to do a better job sharpening the final image than what the camera processor can achieve.

Not trying to start a RAW versus JPEG battle – the engineer in me just needs to know how this works.

 

[smoke665]

Since Large Image Size is 12mp, and I have attempted to pixel peep the raw file to be certain, but it seems that the effective pixel density is the same for the JPEG Large setting and the RAW image

You're not viewing the RAW file itself, you're viewing a JPEG preview image embedded in the file, which likely has at least some manufacturers proprietary algorithms applied.

 

[21limited]

The final jpg will be the same as the raw, for the first edit. If you come back to the image after you've deleted the raw file, and edit further there may be artifacts and that will completely destroy your resolution. Big ugly squares in your darker areas. And I find in some settings, trying to use a really small size jpeg will produce banding and artifacts right from the raw. I generally try and get my images down to 1m MB or posting on-line. Sometimes Ihave to go a bit more, as high as 1.7 MB to avoid banding.

 

[greybeard]

The final jpg will be the same as the raw, for the first edit. If you come back to the image after you've deleted the raw file, and edit further there may be artifacts and that will completely destroy your resolution. Big ugly squares in your darker areas. And I find in some settings, trying to use a really small size jpeg will produce banding and artifacts right from the raw. I generally try and get my images down to 1m MB or posting on-line. Sometimes Ihave to go a bit more, as high as 1.7 MB to avoid banding.

Yes, editing in jpeg is a lot like trying to edit sound using mp3 instead of .wav files. The compression/uncompressing process during editing creates more and more artifacts with each generation.

 

[DBY]

Thanks - so I was thinking about this the wrong way - that the pixel count for Large, Medium and Small were somehow achieved optically or photographically but as you point out all JPEGS are algorithmic translations of the original RAW file and Nikon's Large, Medium and Small settings are just primary inputs to be taken into consideration when making that translation. Strictly from a pixel density perspective a Large file does have equal pixel density to the RAW file but then a lot of other things happen when you look at the final JPEG. Thanks

 

[Ysarex]

Thanks - so I was thinking about this the wrong way - that the pixel count for Large, Medium and Small were somehow achieved optically or photographically but as you point out all JPEGS are algorithmic translations of the original RAW file and Nikon's Large, Medium and Small settings are just primary inputs to be taken into consideration when making that translation. Strictly from a pixel density perspective a Large file does have equal pixel density to the RAW file but then a lot of other things happen when you look at the final JPEG. Thanks

A lot of other things happen indeed. It's just a novelty, but you can display and look at unprocessed raw data. It's very dark but you can make out the image and if you zoom in real close you can see the color filter array. (Download it, put it in an editor and lighten it up). To get some perspective on just how much in the way of other things needing to happen here's an unprocessed raw file, the JPEG the camera made, and the JPEG I made.