What's the point of all those pixels

Geoffc

Senior Member
A common thing I see written about the D800 or even the D7100 for that matter is "what's the point in all those pixels". In truth I very rarely need them myself as I don't print big, however they are very useful to me for the following reasons.


  1. If I ever do manage to take a great image and want to print big I've got it available.
  2. If I need to crop I've got plenty to play with. Sometimes I take things like buildings with plenty of space around so I can straighten them in post. In reality, if I always need to crop because I can't get close enough I would be better with the high resolution per mm of the D7100 and thats what I use for shooting small stuff, but the D800 gives me the option.
  3. Noise. This is one of my biggest things these days since I realised the impact of sizing. As most of my stuff goes on Facebook, online competitions or Flickr, the biggest dimension is about 1600 pixels. If I go into Photoshop and change the image size down to this it removes lots of noise. My ISO 6400 images are stunning (in my mind) with regards to noise. I've been a little late realising this, but it now allows me to shoot with a very relaxed attitude to ISO.
  4. Sharpness - Doing the resize described above also makes the world look sharper.

The thing with points 3 and 4 is that an image should be processed based on what distance it will be viewed. If you print very big and stand a long way back a noisy image will look much better. However, if you view a D800 image at 100%, 18 inches from your eyes and it's anything short of perfect in terms of noise and sharpness and it won't look great. Lots of new owners say they are not impressed and this is why.

The other thing I love about this sensor is the dynamic range and the ability to recover blown or underexposed detail; that's just wow.
 

WayneF

Senior Member
  1. If I ever do manage to take a great image and want to print big I've got it available.

Right. And just to elaborate on your point 1, the D800 image is 7360x4912 pixels on a 35.9x24 mm sensor. So this is 205 pixels per mm.

Without getting bogged down in it, let's claim a sharp lens can resolve 100 line pair per mm. So this is 200 lines per mm, and if those lines were somehow precisely aligned with the sensor pixels, the D800 sensor can resolve them. But of course, they cannot be aligned, and the Nyquist rule is we need at least a minimum of 2x this sampling frequency (and more is better).
So... the D800 really is not enough to resolve what a good lens (in good conditions) can do. Which to do so could be a goal.

But if all we are going to do with the image is to show in on a video monitor screen, or to print it 6x4 inches (both being greatly smaller images), then yes, a much smaller camera would suffice. But then again, that is all you would get. :)
 

Geoffc

Senior Member
Right. And just to elaborate on your point 1, the D800 image is 7360x4912 pixels on a 35.9x24 mm sensor. So this is 205 pixels per mm.

Without getting bogged down in it, let's claim a sharp lens can resolve 100 line pair per mm. So this is 200 lines per mm, and if those lines were somehow precisely aligned with the sensor pixels, the D800 sensor can resolve them. But of course, they cannot be aligned, and the Nyquist rule is we need at least a minimum of 2x this sampling frequency (and more is better).
So... the D800 really is not enough to resolve what a good lens (in good conditions) can do. Which to do so could be a goal.

But if all we are going to do with the image is to show in on a video monitor screen, or to print it 6x4 inches (both being greatly smaller images), then yes, a much smaller camera would suffice. But then again, that is all you would get. :)

Wayne, I don't want to get bogged down either and I honestly don't know what point your trying to make:confused: Mine was nothing to do with lens resolving power, rather that if you have a lot of pixels that you can afford to chuck away, you throw away noise and sharpness errors while your at it. For example, if you cause blur across a couple of pixels because of movement you eliminate some of that by downsizing. My resolution point was comparing the pixel density of the D800 and the D7100.

I was not suggesting getting a lower resolution camera, far from it. I was saying that if you take a 7360x4912 image you can downsize and still have a good image with less noise. If you start with a small image the trick doesn't work very well!! I was saying the D800 is good for this and I have one.
 

WayneF

Senior Member
Wayne, I don't want to get bogged down either and I honestly don't know what point your trying to make:confused: Mine was nothing to do with lens resolving power, rather that if you have a lot of pixels that you can afford to chuck away, you throw away noise and sharpness errors while your at it. For example, if you cause blur across a couple of pixels because of movement you eliminate some of that by downsizing. My resolution point was comparing the pixel density of the D800 and the D7100.

I was not suggesting getting a lower resolution camera, far from it. I was saying that if you take a 7360x4912 image you can downsize and still have a good image with less noise. If you start with a small image the trick doesn't work very well!! I was saying the D800 is good for this and I have one.

Relax. I am agreeing. I am only saying to make more use of the lenses full resolving power is another reason for more pixels. If the lens can do it, we might want to capture it. :)
 
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randyspann

Senior Member
The other side of the coin... 34mp on a full frame sensor vs. 16mp on the same size sensor means each photosite on the 16mp is larger and able to 'receive in' more light. Hence better low light performance. ie. D800 vs. Df.
 

Geoffc

Senior Member
The other side of the coin... 34mp on a full frame sensor vs. 16mp on the same size sensor means each photosite on the 16mp is larger and able to 'receive in' more light. Hence better low light performance. ie. D800 vs. Df.

The D800 is actually 36mp rather than 34. In many tests you find that when you downsample (As per my original point) the 36mp file down to 16mp it comes out rather well. I'm not saying it's better than the native 16mp FX sensor but it does a very good job. On that basis the D800 is a respectable high ISO camera but not a class leader. As I didn't particularly buy it for that purpose alone I'm good with that. On the other side of the coin, the 16mp sensors are complete garbage when it comes to taking high resolution images at 36mp ;) Or to put it another way, what's clever about a low res sensor that has pixels the size of buckets? It's a bit like bragging about designing a car that has a top speed of 25mph but delivers 100mpg. And yes I am just teasing and don't want a debate about the merits of the D800 vs the DF and to prove it I haven't banged on about rubbish like dynamic range and colour depth etc etc :cool:
 

WayneF

Senior Member
And of course, techology times are changing too. DxO reports the 36 megapixel D800 sensor significantly ahead of the 12 megapixel D700 sensor, in every category. Larger is only one factor any more.
 

aroy

Senior Member
Even I find that excess pixels are of some use. The crops come out well and you can always print big if required. For example on my D3300, the 24Mp sensor gives me plenty of pixels when I shoot a bird with 35mm/50mm lense. It may fill 1/4 of the sensor horizontally, but that itself is 1500 pixels, more or less the maximum you use for internet displays. In case it was a lower MP sensor, I would need bigger lenses for similar number of pixels.
 

Scott Murray

Senior Member
This is my point...

SHM_6501.jpg




SHM_6501-2.jpg
 

Geoffc

Senior Member
Even I find that excess pixels are of some use. The crops come out well and you can always print big if required. For example on my D3300, the 24Mp sensor gives me plenty of pixels when I shoot a bird with 35mm/50mm lense. It may fill 1/4 of the sensor horizontally, but that itself is 1500 pixels, more or less the maximum you use for internet displays. In case it was a lower MP sensor, I would need bigger lenses for similar number of pixels.

A good point and the 24mp DX sensors are actually better than the 36mp FX for this sort of thing where you can only fill a part of the frame.


Sent from my iPad using Tapatalk HD
 

Sambr

Senior Member
Right. And just to elaborate on your point 1, the D800 image is 7360x4912 pixels on a 35.9x24 mm sensor. So this is 205 pixels per mm.

Without getting bogged down in it, let's claim a sharp lens can resolve 100 line pair per mm. So this is 200 lines per mm, and if those lines were somehow precisely aligned with the sensor pixels, the D800 sensor can resolve them. But of course, they cannot be aligned, and the Nyquist rule is we need at least a minimum of 2x this sampling frequency (and more is better).
So... the D800 really is not enough to resolve what a good lens (in good conditions) can do. Which to do so could be a goal.

But if all we are going to do with the image is to show in on a video monitor screen, or to print it 6x4 inches (both being greatly smaller images), then yes, a much smaller camera would suffice. But then again, that is all you would get. :)

Sorry but what hell did you just say?????
 
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