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Physics

Discussion in 'Open Discussion' started by EasyEd, Nov 11, 2010.

  1. EasyEd

    EasyEd Mu-43 Regular

    78
    Feb 16, 2010
    Hey All,

    Years ago when I had the opportunity and pleasure of learning fundamentals of photography at a University which in addition to all the elements of making photographs in the field and studio included processing and printing my own black and white film, I also took a 3 month course that went into the detailed chemistry of photography including how light chemically affected film, all the detailed chemical reactions and equations, temperature effects etc. I actually thought I understood photography right from the capture of an image through to the final print pretty darn good. Then came digital...

    Now all the chemistry is ancient history and it's all about physics and electronics so I been working on trying gain some understanding of this stuff by reading and working to understand articles like this on the Physical Limits in Digital Photography:

    Physical Limits in Digital Photography - full paper

    I've a long ways to go but think I am getting a lot of it. I'm not as inherently good at understanding physics as I am at chemistry. That said some - just some - of what I'm getting from this are the following points:

    1) Digital photography has the potential to be far sharper than film. The practical meaning of which is that the old rules about speeds at which you can "handhold" are no longer valid. So if for example you could handhold at 1/60th with film and you could with digital get twice as sharp an image you probably need to be hand-holding at speeds of 1/250th or faster or you suffer some movement blur reducing your image to the sharpness of film. So maximum sharpness seems to mean more use of a tripod I wanted to throw away if light levels are low. Dang!

    2) There is a fundamental trade-off between depth of field (DOF) and sharpness. Increased DOF means less sharpness once the diffraction limit of the lens is surpassed. With the increased sharpness potential of digital this diffraction limit has meaning if you want truly sharp images front to back. This is apparently around F7 or F8 for micro4/3rds - F10 full frame. Smaller apertures (bigger F-stops) means loss of sharpness. Not sure how hyperfocal distance fits into this yet. Anyway with film simply using small apertures gave you adequate sharpness since the film wasn't very capable of rendering sharper images anyway. Hence to obtain sharper images all the way through an image with digital you need to go to tilt-shift lenses or use focus slice methodologies. Focus slice again means use of a tripod I wanted to throw away since it is based upon repeated images. :frown:

    3) There is a fundamental trade-off between high ISO (low light) performance and dynamic range. Improvements in high ISO performance means less dynamic range even if you have a digital camera capable of covering a lot of dynamic range. Krap As primarily a landscape guy I want both high ISO performance and dynamic range. Actually I can have both but only as in the case of sharpness using focus slices if I take repeated images changing exposure of the same scene and HDR like combine them. That takes some time and camera movement messes it up so it's back to the friggin tripod that I wanted to throw in the garbage. :frown::frown:

    To top it off we are apparently very near the physical limits of what current technology can even do so the future potential of throwing the tripod away isn't promising. Of course there are other nuances that I haven't mentioned and I'm sure there is a lot more to learn.

    So what I'm getting is that digital can and does outperform film and did according to some even at 3 megapixels but to - from a real world perspective - maximise this benefit actually requires more work than simply accepting film like or a little better performance from a digital camera that is capable of much higher image quality. Dang!

    What I was hoping for was increased Sharpness, DOF, Dynamic Range and higher ISO performance ALL at the same time allowing me to simply point and shoot under all kinds of light conditions and enjoy the site of the trash truck hauling away the tripod. Couldn't these engineers have figured out someway to repeal the laws of physics I don't like? :rolleyes:

    I guess it comes down to deciding what level of IQ is "good enough" and perhaps just not having to deal with film is benefit enough for most? Now to figure out where I want to be.

    I welcome any comments and/or corrections.

    -Ed-

    PS Why doesn't every digital photography site have a sticky that lays out all these fundamentals for photography experienced digital beginners like me?
     
    • Like Like x 4
  2. JoepLX3

    JoepLX3 Mu-43 Top Veteran

    509
    Jun 13, 2010
    Japan
    Some remarks on your comments
    - I can also be wrong...

    1) Do you mean sharpness at pixel level or A4 print viewed at 1 m distance?

    2) If High ISO performance is as good as low ISO level then you can use shutter time for motion blur (slow if you want blur or fast if you don't want blut) and you can use aperture to control DoF (open if you want narrow DoF for glamor portraits or narrow if you want sharpness from in front of the lens to infinity).

    3) I don't see how good high ISO performance degrates dynamic range at low ISO levels.

    I don't see drawbacks of digital being "better" than analog as long as you don't go pixel peeping in the MB pixel race...
    - Oh, especially P&S with small sensors are good at increased sharpness at large DoF (and in less extend better Dynamic range and High ISO performance)
    - But for real photographer this is not what they want, they want control and then you have to hold the steering wheel (if you know what I mean)

    Sensor size is one aspect you forget and main driver on that is costs (and companies try to sell smaller sensors camera at premium prices by stating it is more compact).

    If you don't want shallow depth of focus (large aperture icw large sensor and mid-long focal distance) and don't see the value of (E)/OVF then go for a P&S (or bridge camere with fixed large zoom range lens).

    PS: Current DSLR's might indeed not improve much more on High ISO performance & Resolution given certain sensor size (with lens portfolio). Besides auto focus also the good old primes have not seen much improved lenses either. So business with every year a new camera is mainly about gadget specification and buying a different lens to extend your applications might be more wise than upgrading the camera every year.