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Posts posted by herbko

  1. I still don't think your get my point regarding Digic. Canon uses the Digic brand regardless of whether the sensor is their design or not. It's nothing more than a branding of their DSP, it doesn't indicate anything in particular. It has been very effective, though, and now Nikon is emulating it. Of course it's nice to have design commonality between products, but having worked closely with VLSI design groups before, I don't think it's that big a deal. Once they do a few of these kinds of parts, they get good at it.


    I think I share you view about this branding gibberish. The point I'm trying to make is that the image processor's tasks are dependent on the sensor design. Canon is up to Digic III. All the Canon CMOS cameras have one of the three chips. If Nikon did the same thing they may be up over 10 by now, which may make the branding of those chips less effective. The fact they are choosing this time to brand their image processor suggest to me that they've converged on a design, and do not plan to do one CMOS camera followed by a CCD followed a LBCAST.... I also read that the sensors on these cameras are their own design and not from Sony. The two suggest to me that they've finally got their design and process act together and plans to use that in the future.


    If it really is true that the two new sensors are not from Sony. I'll stick my neck out and predict that with the possible exception of the D40x upgrade, Nikon is done with Sony.

  2. They call it "visually lossless" which some who've tested it claim to be true. I'd rather avoid it though. The Leica uses an even more extreme form where they store the square root of the raw data as an 8 bit value in the raw output! Yuck...


    Renaming it to "visually lossless" is their new face saving spin. Have a look back at the D70 introduction. It was just lossless at that point. I guess the spin is working.



  3. I don't see how making both the sensor and DSP lends any special credibility or significance to the "Digic" brand. "Digic" after all, is a name Canon uses in their digicams where the sensor itself is a CCD supplied by Sony. It's marketing pure and simple, though it is effective. Canon is clearly a better marketing company than Nikon and selective branding of technologies is very effective in promoting an image as a technology leader. Nikon is basically ripping off Canon there and I'm glad to see it. Now, when ignorant Canon fans boast that Canon has Digic, ignorant Nikon fans have something in response. ;-)


    Sure. Canon marketing played up their DSP. The point is this is not possible if you're using a different one for each camera you build because each has a different sensor design. The fact that Nikon is now doing this suggests that they will continue with one line of DSP design which I think really only works if they stop switching sensors with every camera.

  4. I think it's interesting that Nikon has taken a page out of Canon's playbook and branded their DSP. Canon has been convincing their faithful that "Digic" is somehow special for years now; Nikon decided that it needed to be equally special with "EXPEED". Both are meaningless; all cameras have pieces whether they name them or not. Perhaps soon Nikon will relabel some of their lenses "L". They already paint the rings.


    I think this is more than sales and marketing at work. The new sensors are Nikon designed processed by their own contract fab. I think they will now converge on this and evolve both the sensor and the DSP and use it all the new designs as Canon has done all along. Previous to this they been using CMOS and CCD from Sony as well as their own LBCAST which probably required different DSP's. Going forward I think they'll dump Sony and go with their own for all new designs.


    It makes sense. I wouldn't depend on a competitor for such a key component in a market with so few players.

  5. Im definately waiting for the D3x announcement to see what that'll be like.




    Since the housings probably won't be ready until that time, there's no rush. If it's roughly the same camera with more pixels and more noise and lower dynamic range which would you choose?


    Looks like Canon will have to adjust their prices on the 1DsIII in light of this new competition.

  6. Interestingly, Sony's new CMOS DX sensor has many parallel ADCs. I wonder if that implementation results in a lower noise conversion since the ADCs are clocked much slower.


    First, they are 12-bit converters, and the state-of-the-art in that is probably good enough to be not much of a factor. Also, multiple A/D's have threshold matching problems which can show up as noise or patterns. Since, Sony is sending this out they're likely to have a good handle on it, but it's not clear that is not a noise contributer.

  7. Each of these sources say that 12 bits is equivalent to 74 dB. Where the 2dB difference is I don't know and don't really consider important. It's a constant in the equation though. Each bit is 6dB. The important thing is that 78dB means 12 2/3 stops, not 13.


    The 6 db/bit is the range. The difference is that to get to the maximum signal-to-noise, SNR, that most specs quote, you have to divide by the quantization noise which is a fraction of a bit, so that number is about 2db higher.


    I really don't think we can assume anything about the effective difference between current 12 and 14 bit converters. Julia reports 2/3 stop improvement for the 1D3 over the 5D and Clark reports that the 5D achieves nearly 12 stops. If Julia is to be believed, the 1D3 is only achieving about 12.5 stops. If there is really a 1.5 bit advantage like you say, then the 1D3 should do better. Perhaps it does.


    It could be limited by the sensor or the A/D. If a careful test gives 12.5 bits we still won't know which it is.

  8. I have seen specs as high as 78dB for 12 bit converters as well. That would exceed their resolution though.


    Assuming 12 bit converters can do 74dB or better and 14 bit converters do 78dB, a 14 bit converter only offers 2/3 stop over 12 bit. Julia Borg, the source of this information, claims that an engineer gave her these numbers and it corresponds to her observation that the 1D3 only offers a 2/3 stop improvement over the 5D.


    Perhaps the reason we haven't seen 14 bit converters before now is that they have been impractical as well as unjustified in these systems. I would think this would improve with time, but for now expecting a 2 stop improvement with 14 bit is, perhaps, too optimistic.


    FYI: Julia Borg is a knowledgeable photographer and contributor at the dpreview forums. Her father, Iliah Borg, is the author of Raw Magick, a well respected raw converter for Windows.


    The maximum dynamic range of a 12-bit A/D is 20*log(2^12) = 72db. State of the art for high speed ones seems to be around 70db.




    The 14 bit converters are probably ~1.5 bit better than the 12-bit ones.


    The 5D cell area is about 30% bigger. The new generation sensor design from Canon may not have improve things that much.

  9. I read from a generally knoledgable source that today's DSLR 14 bit converters are limited to 78dB which would be about 13 bits. If that's true (which would be a bit surprising to me) then the value of 14 bits is only one stop over 12, not two like it should be. Any idea whether that's the case?


    That seems to be close to the state-of-the-art:




    The 12-bit A/D don't have 12 effect bits either, so the 14-bit ones are about 1.5 bits better.



    Well, I just heard that the official annoucnement will definitley be tomorrow (8/23rd). Little that I heard sounds promising. It won't compete with DsIII in certain aspects but otherwise it should hold up very well against anything else that Canon has to offer. It is a good thing I did not buy the 17-55mm yet either :(


    Has anybody checked amazon.com :)

  10. If what you are saying is that 14-bit gives you a 2 stop improvement in ISO performance, as would be suggested by your explanation, then absolutely not. If that were the case, all we'd need for great high ISO would be 20 bit converters!


    The output of the sensor, after amplification, is referenced to a set voltage which is the maximum voltage the ADC responds to. This is independent of the number of bits in the converter. The "extra" bits added in the 14 bit converter, therefore, aren't at the "top", they're at the "bottom".


    Perhaps I didn't word that very well. I'm not saying that the 14-bit converter will give 2 stops better ISO performance, and I agree that the extra bits are at the "bottom" of the range. Let me try again with an example....


    Set the 14-bit camera at ISO 100 and the 12-bit camera at ISO 400. If the exposure is correct for ISO 400, both cameras will give the same signal-to-noise raw outputs with the same number of useful quantization levels with the top two bit of the 14-bit camera always 00. However, the shot of the 14-bit camera will not be over exposed if the "correct" exposure happened to be ISO 100. So in effect you can shoot ISO 100-400 exposure at ISO 100 setting and get at least a good 12-bit output. If the exposure level is ISO 400, the 14-bit camera will not give a better output than the other one. If you happen to over expose what you thought was an ISO 400 exposure, you're protected by a couple of stops. I think the high dynamic range mode in the 1DIII is doing something like this.


    What's more interesting is that you can think of exposing the bright parts of you image at ISO 100 ( the sunball for example ) and dark parts at ISO 400, and bring the ISO 400 parts up to ISO 100 in post processing. The signal-to-noise of the dark parts will be no better than an ISO 400 exposure, but it would not be limited by quantization problems.


    The analog voltage representing 2 stops below maximum will be 1/4 of maximum voltage regardless of bit depth or ISO. If a sensor has less than 12 stops of range, then both the 12 and 14 bit converters will be digitizing noise in their lowest bits.


    As I mentioned before even if the sensor has less than 12 stops of range as defined by the RMS noise level, there is still information below this level. It's better to record it than to cut it off, especially in cases where you have to bring up the darker levels for dynamic range reasons.

  11. The 40D has 14 bit now but I'll be surprised to see that it helps that sensor in any way. If Canon can exceed 12 stops at base ISO with a 10MP 1.6 sensor then they've made impressive progress.


    The area of the 1.6x sensor is about 2/3 the area of the 1.3x sensor, so the signal-to-noise of the 40D should be within one stop of the 1DIII at the same exposure and ISO. Even if by the usual definition of dynamic range, max signal/noise level, the sensor is not quite 12 bits, there is still information below the RMS noise level and the extra resolution will still help. It'll make the parts below noise level fuzzy instead of banded.


    Looking at it another way, with a 14-bit A/D the parts of a shot that are 2 stops under exposed will have the same sensor output as the same sensor with a 12-bit A/D set to 2 stops higher ISO. Assume the same sensor, the output of an ISO 100 shot with the 14-bit A/D will be no worst than an ISO 400 shot with 12-bit A/D. If nothing else, it will give you room for underexposure in cases where you want to really be sure to preserve the highlights.


    I'm not surprised that Canon put the 14-bit A/D in the 40D. It probably cost them less to make just one Digic III and associate IO that process 14-bit and use it for all the camera than to make 2 versions. The only incremental cost is a little more memory for the same shot buffer.

  12. I think you may be confusing the 8-bit color graphic scheme with the 8 bits per channel format of common photo encoding like JPEG. For display and print, 8 bits per channel is enough. I'm not aware of any display or print devices that are much better than that. 16 bits per channel is better when you are adjusting the image. After the final adjustments are done, you shouldn't see a difference in converting to 8-bits.

  13. What advantages would this camera have over your 1DsMkII for underwater use? Note I'm not saying the MkIII isn't an excellent camera (despite the potential teething problems with at least some units), but I'd be interested to know which of its features are of benefit for underwater use, especially compared with other cameras.


    The low noise sensor and 14-bit A/D converter is a combination that's unmatched for the capture of images with large dynamic range, like sunball shots. The 1.3x crop format does not have a lens that's optimal for sunball shots. I'd wait until Canon puts the new sensor and A/D into the 5D and 1Ds2 replacements.

  14. I see from the EXIF of the photo that you shot that with an 85mm lens. The shark is too far away; there's too much water between the lens and the subject. You'll have to get closer with a wider lens. For your Canon 300D the typical lenses for that kind of shots are 15mm fisheye or 10-22 zoom.

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