12 bit vs. 14 bit

[francisco_disilvestro]

<blockquote>

<p>But back to the original quesiton: the D300/D300S does not even have 12 stops of dynamic range. Therefore, the DR argument is moot.<br /> Additionally, as far as I know, the D300 and D3X's sensors can only capture 12 bits. The extra two bits are merely calculated. That is why those DSLRs' frame rate slow down dramatically in 14-bit mode.</p>

</blockquote>

<p>The case with D300/D300s is an interesting one. There are different guesses about how those camera handle the 14 bit conversion, as the in-sensor A/D converters are 12 bit.</p>

<p>Since Nikon does not disclose how they do, we cannot be sure. Anyway, one of the guesses that IMHO is the most likely, is that it uses a proven technique of performing multiple A/D conversions (in this case 4) of the same analog sample (that´s why the speed is reduced by almost 4 times).</p>

<p>The idea would be to average those 4 samples with the end result of some reduction of read noise.</p>

<p>To avoid increasing processing time even more, the division is not performed. The 4 samples are just added, and that´s why you go from 12 to 14 bits (imagine adding 4096 four times you get 16384, equivalent of 14 bits)</p>

<p>So in this case, what you really have is a 12 bit significant number with less noise, not 14 bit.</p>

<p>Anyway, let me emphasize that this is just a guess of how the Nikon D300/D300s gets the 14 bits. It may be a completely different approach.</p>

[photo5]

<p>Interestingly, dpreview.com measured a higher dynamic range from the D300 than from the D700...</p>

[francisco_disilvestro]

<p>According to DXOMark data, what happens with the D700 is that at low ISO read noise is higher than shot noise, so the camera is not able to take full advantage of its sensor capabilities.</p>

<p>For a comparison of DR between the D300s and D700 go <a href="http://front1.dxomark.com/index.php/Camera-Sensor/Compare/Compare-sensors/(appareil1)/441%7C0/(appareil2)/614%7C0/(onglet)/0/(brand)/Nikon/(brand2)/Nikon">here</a> (select Dynamic Range), you can see how the DR vs. ISO curve of the D300s is linear. The curve of the D700 becomes linear after ISO 800</p>

<p>If the D700 had lower read noise, one could extrapolate the values and it could reach almost 14 bits of DR alt base ISO</p>

<p>Anyway, even for 12.15 stops of DR at base ISO for the D700, you need at least 13 bits</p>

<p>From these graphs it should become evident that a bit depth of 14 bits makes sense only at low ISO. (I.E, the D700 at ISO 3200 has a DR of 9.44 stops, not even 12 bits are needed)</p>

[jay_hector]

<p>One other issue with 14-bit on the D300 (and I'm sure the S too) is that the shutter lag just about doubles from 45ms or so to 85ms. That is even worse to me than 2.5fps.</p>

[Ed_Ingold]

<p><em>Sorry, but it doesn´t work that way in RAW capture. Every stop of dynamic range is defined by doubling the light intensity from the previous f stop.</em></p>

<p>I think you meant to say that each bit represents a doubling of intensity. Regardless, your understanding of image encoding is completely false. You continue to build arguments based on a false assumption.</p>

[photo5]

<blockquote>

<p>One other issue with 14-bit on the D300 (and I'm sure the S too) is that the shutter lag just about doubles from 45ms or so to 85ms. That is even worse to me than 2.5fps.</p>

</blockquote>

<p>Yes, it's very disturbing, which is another reason I don't use it. 12 bits is enough for me in any case, it sure beats 8 bits!</p>

[francisco_disilvestro]

<blockquote>

<p>I think you meant to say that each bit represents a doubling of intensity. Regardless, your understanding of image encoding is completely false. You continue to build arguments based on a false assumption.</p>

 

</blockquote>

<p>So you don't agree that for a 14 fstop DR you need at least 14 bits in linear (RAW) capture?</p>

<p>Note: Bith depth will not increase DR, but it could limit it</p>

[luke_kaven]

<p>Edward, I was also wondering why you thought each bit did not represent a doubling of intensity. The numbers coming off the sensor are linear, so why wouldn't that be the case for those numbers?</p>

[pat_warner]

<p>And what is bit depth, in English?</p>

[francisco_disilvestro]

<blockquote>

<p>And what is bit depth, in English?</p>

</blockquote>

<p>It is the number of bits used to quantify the signal. In the case of Nikon models like D3 series, D300 series and many others, it could be either 12 or 14 bits for RAW (You select it via menus)</p>

<p>The maximum number that can be represented with 12 bits is 4095 (or 2^12 -1) and 16383 for 14 bits (2^14 -1)</p>

<p>JPeg uses 8 bits, but the issues discussed here (about the relation of Dynamic Range and minimum number of bits) don´t apply directly since it is a processed format where a nonlinear curve has been applied.</p>

[pat_warner]

<p>Per pixel?</p>

[ShunCheung]

<p>Right 12 bits or 14 bits per pixel. Please keep in mind that we are talking about Nikon DSLRs whose sensors have the Bayer pattern so that each pixel has only 1 color channel.</p>

[ellis_vener_photography]

<p>i bit + either black or white , either 0 or 1, (2 tones)<br>

2 bits = black, 2 shades of gray, and white ( 4 tones )<br>

3 bits = black, 6 shades of gray, and white (8 states of tone)<br>

4 bits = black, white, and 14 shades of gray ( 16 states of tone)<br>

5 bits = 32 tones<br>

6 bits = 64 tones <br>

7 bits = 128 tones<br>

8 bits = 256 tones ( expressed as 0-255)<br>

9 bits = 512 tones<br>

10 bits = 1024 tones<br>

11 bits = 2048 tones<br>

12 bits = 4,096 tones<br>

13 bits = 8,192 tones<br>

14 bits = 16,384 tones<br>

15 bit = 32,768 tones<br>

16 bit = 65,536 tones</p>

<p>Now here is the thing to understand if it has not been mentioned earlier. every photo site ,or pixel as you are calling them , in a sensor is actually monotone. It can only see / record a shade of gray. The color is made by capping each photo site with a red, green, or blue filter. 99 times out 100 the ratio is 1:2:1 or 1 red, 2 green , and 1 blue. This 1:2:1 ratio has been found to pretty well match the sensitivity of the healthy young human visual system to color.</p>

<p>Color for each point ( photosite /pixel) is created by an algorithm that looks at the values of a pixel and the pixels that surround it and and makign an estimate of what the other two color values should be. This ordering of filters and interpolation of color color values is called respectively the Bayer Matrix and Bayer Demosaicing algorithm. It is called "Bayer" because if you think about this too much for long periods of time you will get a massive headache.<br>

So this means that any color in a 14 bit per channel image are made up of a combination of any of 16,384 x 16,384 x 16,384 tones.<br>

More bits are important for three main reasons:</p>

<ul>

<li>the more samples the smoother rendition of a range of tones or color</li>

<li>the more fine details in the highlights the camera's visual system ( light recording sensor, analog to digital conversion and other signal processing and encoding processes ) can be recorded as discrete values ( data is denser i nthe highlights than in the shadows).</li>

<li>the more data (meaning after raw processing) Post- processing programs like Photoshop have as disposal headroom to absorb rounding errors in the millions of calculations necessary to create the final photograph. </li>

</ul>

[pat_warner]

<p>I shoot a 300S x 14 bit uncompressed Raw NEF's, not because I know squat about what you're talking about (yet) but, indeed the tonal range is stretched out, facilitating more editing latitude. I do appreciate your (Ellis) effort , et. al. and will continue to follow this most interesting thread, one that Nikon ignors.<br>

<a href="http://patwarner.com/new_pix.html">Some minor pix.</a></p>

[ellis_vener_photography]

<p>Pat You do have more editing latitude, but it is not because the end points are stretched out , by which I think you mean further apart, -- absolute detail-less black and absolute detail-less white are still absolutes but because the gradations in between the two absolutes , the sampling rate of the continuous range of tone is ever more fine creating a better illusion of continuous tone and color, even after the (usually) unintentional damage done by the processes involved.</p>

[ellis_vener_photography]

<blockquote>

<p><em>Pat You do have more editing latitude, but it is not because the end points are stretched out , by which I think you mean further apart,</em></p>

 

</blockquote>

<p>On reflection , I see that I am wrong about this. A 14 bit capture obviously has a longer tonal scale than a 12 bit capture- -there is more distance between absolute black and absolutely specular no detail white. It is just that the extra dynamic range is concentrated mostly in the highlights where as I said before, there is a lot more data / information.</p>

[photo5]

<p>I want to SEE the evidence with my eyes. I don't want to just see NUMBERS. I don't see any advantage until I can see PROOF.<br>

Anyone?</p>

[ShunCheung]

<blockquote>

<p>I want to SEE the evidence with my eyes. I don't want to just see NUMBERS. I don't see any advantage until I can see PROOF.<br />Anyone?</p>

</blockquote>

<p>Dave, how about run some A/B comparisons to convince yourself?</p>

<p>When can we expect your results?</p>

[photo5]

<p>Shun, I'm slammed in school right now, just have enough time to take a break and read Photo.net forums :-)<br>

I figured there are plenty of people here who say they shoot in 14 bit and notice a difference who could share their results.<br>

I did do a test with my D300 in 2007 shortly after purchasing it, shooting at various ISOs in a dimly lit room. At least in shadow, there is absolutely no difference between 12 and 14 bit whatsoever! I didn't test it with highlights at ISO 200 outside, though. Hadn't thought of that. Will do a test next summer while hiking near Mt.Rainier. Lots of highlight information on that mountain in the sunlight.</p>

[ShunCheung]

<p>Dave, the problem is that over the web, we are severely limited by the 8-bit JPEG images we can post. There is no way you can show the difference between 12-bit RAW and 14-bit RAW with 8-bit JPEGs. Therefore, you pretty much have to do some experiments yourself.</p>

<p>My background is from shooting slide film with 5 stops of dynamic range. Having 7, 8 stops of dynamic range is already a luxury. I think you have to look pretty hard to find subjects with 14 stops of dynamic range to see a difference.</p>

[pete_s.]

<p>This is a good read:<br>

http://www.earthboundlight.com/phototips/nikon-d300-d3-14-bit-versus-12-bit.html</p>