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Real world-FF vs Crop ISO

Discussion in 'Help Team' started by CanonGary, Mar 29, 2017.

  1. Learning

    Learning Ethelred the Ill-Named

    Every image has noise present. You make the point that noise does not matter when, as usual, the presentation of the photograph does not disclose the noise. Same goes for defocus.
    I cannot comment about the Cannon cameras since I use Nikon. Also I have never used a Nikon Df but I would expect it to have a very good noise characteristic. My present D500 cameras are also low noise. I would expect D5 to be better because the photosites are bigger and both cameras are of the same generaation. The Df photosites are also bigger but the sensor is of an ealier generation.
    Now back to Gary and his original question. It seems no one here has both a 7D Mk2 and also a 5D Mk3. I would expect the 5D Mk3 to be better than the 7D Mk2. Whether the difference matters depends on the size at which you present your photographs, and the low light conditions under which you carry out your most challenging photography.
    Gary. Can I suggest that you hire a 5D Mk3 and do some tests which are relevant to you. Also if you do so I guess that it would be very helpful to other Cannon users if you were to publish your comparisson in the user review room.
     
  2. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    This is the one thing I've long wondered about with digital cameras. Wearing my techy hat, I can't see any mechanical, electronic or programming reason why a dSLR couldn't be designed with a user upgradeable sensor. The only difference from current types would be the provision of a socket and a dust sealing system to introduce the sensor through. With film, when the "sensor designs" were upgraded you just fitted them into the existing cameras. I'm sure there's sound commercial reasons for not putting the effort in for digital but it seems like a shame to design a camera such as the Leica M9 and then make it obsolete when a higher resolution sensor comes along.
     
  3. Benchista

    Benchista Which Tyler

    It's been done - Kodak did it with their full frame DSLRs, the 14N, DSLR/N and DSLR/C. Only the 14N ever had an update available, though, and that to the same sensor as the other two models. It was a commercial failure, not least because the cameras were only really usable at base ISO due to noise - which is an interesting point in this discussion. The huge problem is that you don't need to just replace the sensor, but typically the processor too to get the best results - the imapact of the processor should not be underestimated, even on RAW files.
     
  4. SqueamishOssifrage

    SqueamishOssifrage Well-Known Member

    Ah yes. My dream - interchangeable digital backs for my Rollei 2000 system. All my lovely Zeiss primes back in action - and don't change ISO, change backs, with backs optimized for three stops - 100, 200, 400 then 800, 1600, 3200 und so weiter.
     
  5. PeteRob

    PeteRob Well-Known Member

    I saw an on-line video once of (I think) a 5DIII being taken apart by one of the camera hire companies. They were looking to learn how it was put together because they did in-house repairs. I think any camera body shell with an end-user replaceable sensor (and the mother board etc. that goes with it) and any other bits that need upgrading, like the power supply, would have to be simply enormous to allow room to move and space for component size changes. How you'd align everything to the correct precision would be a technical challenge too.
     
  6. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    I can't see why the motherboard and power supply would need changing. Yes, you'd need new firmware but that could be built onto the sensor carrier. As to size, there's no reason why you'd need any more space than currently used, if you adopted a carrier that just slotted into the base of the camera. This paper suggests that there's no real difference between a sensor and any other component when it comes to control, data and power: http://www.ftdichip.com/Support/Doc...158_What_Is_The_Camera_Parallel_Interface.pdf
     
  7. EightBitTony

    EightBitTony Well-Known Member

    I get the feeling that outside of embedded cameras, the sensors, associated electronics, and connections, are a little more complex.

    From that PDF,

    "Full VGA (640x480) at up to 15fps can be achieved with the FT900 series camera interface"​
     
  8. beatnik69

    beatnik69 Well-Known Member

    Did Ricoh not produce a camera a few years ago along these lines, albeit not a DSLR?
     
  9. Benchista

    Benchista Which Tyler


    Sort of, but not really - there were various modules to choose from, but they never really made updates for it.
     
  10. PeteRob

    PeteRob Well-Known Member

    On reflection this proposal is not much different to a Phase One back.
     
  11. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    All modern processors look like a data bus, a control bus and a range of independent ports to the outside world. A sensor package needs to be attached directly to a data buffer and that has to connect to each bus. The data buffer and sensor is a flat package. All that's needed is to put the assembly in a frame, possibly with some flash memory to hold the replacement firmware and fit an appropriate connector at the top. Everything else is just the same as at the moment.
     
  12. Benchista

    Benchista Which Tyler

    Except, crucially, the processor...
     
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  13. Benchista

    Benchista Which Tyler

    I'm trying to track the article down, but I'm pretty sure Canon were asked about the idea of replaceable sensors about a year or so back. Their response was (IIRC) that to make it work, you had to replace so much of the camera that it was cheaper just to buy a new one.
    In the case of the Kodak that I mentioned before, the data buffer was the first (and most common) upgrade, and was certainly separate to the sensor package. But the point is that it's the processor that's responsible for the rate of read from the buffer, which is the primary reason why it needs to be upgraded when you upgrade the sensor.
    To get back to the point of this thread, I have owned several cameras with the same sensor, but whose noise performance even in RAW has been different - the original EOS M, for example, is noticably better than the EOS 7D, both with the same 18MP sensor, and the 600D comes in between. Why? The processor.
     
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  14. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    The default design of a digital image sensor chain is sensor -> analogue to digital converter -> data buffer -> processing. Is it the A/D converter you're talking about? That's already effectively part of the sensor package and would be replaced along with the sensor. The camera processor has nothing to do with noise because all it ever sees is a bit stream that it packages into a file on the storage device. It also handles the camera's functions including initiating the sensor read sequence, of course.
     
  15. Benchista

    Benchista Which Tyler

    With all due respect, I would rather believe what the camera manufacturers themselves say: https://www.learn.usa.canon.com/resources/articles/2012/digic_processors.htmlp
     
  16. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    So they've chosen to integrate the sensor, A/D converter, data buffer and CPU together. Doesn't mean it's the only way to do it. To be honest, I own three Eos dSLRs and didn't realise that's what was going on inside so I've learned something in any case.
     
  17. PeteRob

    PeteRob Well-Known Member

    The only practical way to have a fully interchangeable system is to separate the mechanical part of the camera from the electronic, i.e. to have a fully replaceable back. I suspect the reason these failed for 35 mm format is that it overly constrained the size of the camera and was too bulky - a 120 back was already quite a big thing so digital backs on medium format cameras were perhaps not so much of an issue though I think the trend there is now to have an integrated camera. A CSC might be a better base for interchangeable back design as the body basically doesn't do much beyond provide a shutter and housing but again, once you fix the body size there is less room for differentiation.
     
  18. Benchista

    Benchista Which Tyler

    I can show you another article that shows reduced noise because of the inclusion of the AD converter on chip reduces noise, and it's the path Sony have chosen for the same reason. So not the only way, but the most effective way in terms of performance.
     
  19. AlexMonro

    AlexMonro Old Grand Part Deux

    Not necessarily. Consider an image with a lot of fine detail and texture - e.g. grass in a field, sand on a beach, leaves on trees. Noise will be a lot less visible against such backgrounds than it would be against a flat uniform tone, such as clear blue sky. So if, say, you have a picture of a beach scene, you might be able to see noise in the sky, but not on the sand. But just because you can't see it, doesn't mean it's not there.

    Possibly I'm seeing things differently because I spent several years working in a university research lab writing software to remove noise from experimental data that was thousands of times greater than the signals we were interested in. The technique used was slightly similar to darkframe subtraction long exposure noise reduction in photography.
     
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  20. Roger Hicks

    Roger Hicks Well-Known Member

    Dear Alex,

    If you can't see it, it really doesn't matter very much whether it's there or not.

    Also, the brain sees what it wants to see. Film grain can be interpreted as several different textures -- skin, rock, etc. -- but is a lot less acceptable in things we know or believe to be textureless, such as blue skies or shiny chrome.

    Cheers,

    R.
     
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