Dismal shutter lag versus film cameras

Discussion in 'Digital SLR' started by Richard J Kinch, Nov 27, 2007.

  1. My application of digital SLRs is chiefly to fit upgrades to medical and
    scientific instruments that were originally fitted with 35mm film
    cameras (http://www.truetex.com/micad.htm). While for many instruments
    shutter lag is not critical, on certain ones the significant difference
    between film and digital shutter lag is critical.

    I've timed several old film SLRs (by taking 30 fps video and stepping
    through frames) and found that they had a typical shutter lag of only 30
    to 50 milliseconds. On a digital SLR like the Canon 400D I measure this
    at 133 msec (although 100 msec reputed at
    http://www.impulseadventure.com/photo/shutter-lag.html, I can't find a
    Canon spec on this). With mirror lockup on the 400D you can get this
    down to about 60 msec, but that still about twice what the old cameras
    needed without mirror lockup. Some of the higher-end DSLRs improve the
    lag (Nikon sez of the Nikon D2H, "remarkably short 37 millisecond
    shutter time lag is comparable to a fast film SLR").

    Why are DSLRs slower to fire? The mirror and shutter are smaller, so it
    seems they should be faster. Or is this some electronic imaging
    limitation?

    Anything to be done with models like the Canon 400D to speed them up for
    instrumentation?

    The mirror lockup feature on the Canon 400D seems really clumsy. You
    have to push the shutter twice to take one photo. Is there some hack or
    something to get this camera to lock the mirror up for all photos?
     
    Richard J Kinch, Nov 27, 2007
    #1
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  2. Richard J Kinch

    tomm42 Guest


    According to Nikon's literature the pro DSLRs are faster than their
    film brethren. My D200 certainly feels faster than my Canon F1AE. Add
    to that film cameras maxed out at 5 frames per second (with film
    advance), to get 8 frames a second Canon had to put in a a stationary
    1/2 surfaced mirror. Good digital cameras get 8 frames a second
    routinely. I shoot medical photography with mostly digital
    instruments. I would never consider an intrument with a camera as poor
    as a Canon Rebel on it, stricktly amateur stuff. I wouldn't trust my
    work to a camera that is only able to get 25K frames before conking
    out. With the intruments I have the max speed I shoot at is 1 frame a
    second with a 5mp industrial (Megavision) back on a fundus (retinal)
    camera. I also shoot slitlamp photos with first a Fuji S1 1.5fps and
    now a Canon 30D 5fps. Use better cameras you will get better results.

    Tom
     
    tomm42, Nov 28, 2007
    #2
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  3. Richard J Kinch

    TH O Guest

    I don't have one but I recall reading something about a new feature that
    keeps the mirror up while you do all the viewing through the LCD. If my
    recollection is correct, I would think that would solve the problem.
     
    TH O, Nov 29, 2007
    #3
  4. Richard J Kinch

    TH O Guest

    Correct that, I misread 400D as 40D. I believe the Canon 40D has the
    feature I described.
     
    TH O, Nov 29, 2007
    #4
  5. Yup the 40D has live view, but no AF when live view is running...
     
    Not Disclosed, Nov 29, 2007
    #5
  6. I think you may be using manual focus SLRs in manual mode to get very
    short response times. The Contax RTS claimed the fastest of all, and
    that was not much better than your claimed time for the Nikon D2H, which
    is around 1/30th lag. The lag on an old Pentax Spotmatic beats for
    example an Canon AE-1 - very slow, due to trapping the AE needle sort of
    process to set aperture - and the AE-1 in turn beats most AF SLRs. Lags
    of 1/15th of a second (66ms) were common in the late 1970s and early
    80s, and twice that was common - when using the Canon AE-1, we had to
    allow 1/10th of a second delay on break-beam triggering systems to get
    the subject in the frame.

    David

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    David Kilpatrick, Nov 29, 2007
    #6
  7. Also, no external flash sync with live view silent shooting modes (why
    not?). So that's useless for interfacing to instruments.

    Silent shooting disabled with live view does flash sync, but it is even
    slower triggering than the normal mirror-flipping modes.

    Actually, I determined some of the lag was due to remotely activating both
    the half (focus) and full shutter button contacts at the same time
    (electrically in parallel). Even in manual mode the firmware must do some
    thinking when you push the focus button. Leaving it always off or always
    on makes the fastest trigger after the full button contact.

    But at 59 milliseconds on the 40D, shutter lag is still slower than any of
    the old mechanical film SLRs. I wonder if the mechanisms, with their
    motive energy stored in wound-up springs, didn't have faster response than
    the electromechanical solenoids.
     
    Richard J Kinch, Nov 29, 2007
    #7
  8. Faster cycling, not faster shutters.
    I'm talking about shutter lag for the first shot or a single shot, not
    cyclic rates. Film shutters had less shutter lag than digital, even if the
    winder slowed them down on the next shot.
     
    Richard J Kinch, Nov 29, 2007
    #8
  9. Richard J Kinch

    Toby Guest

    The newer dslrs have much better specs. The lag on the Nikon D200, for
    instance, is 50 ms.

    Toby
     
    Toby, Nov 29, 2007
    #9
  10. Richard J Kinch

    TH O Guest

    Out of curiousity, what is the external flash sync activating?
     
    TH O, Nov 30, 2007
    #10
  11. Richard J Kinch

    Ray Fischer Guest

    The biggest difference between today's cameras aand the old ones you
    have been using is probably the fact that today's dSLRs all use
    autofocus lenses while old film cameras didn't.

    If you want less lag then simply turn off the autofocus.
     
    Ray Fischer, Nov 30, 2007
    #11
  12. The instrument is a retinal camera which uses a xenon flash tube and
    optics to put light through your pupil and evenly onto your retina, but
    obliquely through the edge of your pupil so the instrument can
    simultaneously look in through the center of the pupil without getting a
    reflex of the flash.

    Also, the SLR's flash sync contact is a handshake back to the instrument
    that the camera took the shot. That is, the camera was connected, it
    was turned on, it wasn't asleep, the memory card wasn't full, etc.

    The instrument expects the SLR to fire the flash within a maximum of
    about 75 milliseconds of the remote shutter-open signal. Thus the
    typical DSLR (Canon 400D) misses the window with its 100 millisecond
    lag, unless you use the mirror lock up to get 60 milliseconds (but
    that's only every other shutter press and with no way to confirm
    remotely the state of the shutter--very clumsy). A midrange (Canon 40D)
    barely makes it with 59 milliseconds, assuming everything else is
    perfect.

    The original mechanical film camera back, circa 1970s and 1980s, had
    about a 35 millisecond lag from a solenoid operated shutter. I assume
    the spring-loaded mechanisms were more energetic and thus faster.
     
    Richard J Kinch, Nov 30, 2007
    #12
  13. Define less. On a Canon 400D I get a lag of 200 milliseconds in *manual
    focus* with focus+shoot activated together. With focus off and shoot
    activated, it is the rated 100 milliseconds, but if the camera goes to
    sleep it never wakes up. With focus always on the camera never sleeps.
    It's semi-crippled as an instrument interface.
     
    Richard J Kinch, Nov 30, 2007
    #13
  14. Richard J Kinch

    Paul Furman Guest

    Does it make a difference in manual exposure mode? The only 'going to
    sleep' behavior I've noticed is the exposure meter & associated readouts
    and that's pretty quick like 15 seconds or so. I've not seen a DSLR go
    completely to sleep, I've left mine on in the bag for days & it's fine,
    ready to go. USB-activated remote control shooting remains awake for
    extended periods.
     
    Paul Furman, Nov 30, 2007
    #14
  15. Richard J Kinch

    jean Guest

    Have you tried other DSLRs besides Canon? I am sure you tried setting the
    flash sync to first or second curtain, did that make any difference?

    Just curious

    Jean
     
    jean, Nov 30, 2007
    #15
  16. By "sleep" on the Canon 400D and kin I mean the "auto power off" feature.

    On the remote contacts, the shutter contact alone does not wake the camera
    up from auto power off (what I meant by "never wakes up"). You must close
    the focus contact. But closing the focus contact increases the shutter
    lag, regardless of the state of the camera (awake or sleeping, recent shot
    or not) and even in manual focus mode.

    The point being, the instrument inteface, even if the shutter lag is
    acceptable, cannot be a simple switch contact. It must involve some
    intelligence to keep track of the (presumed) state of the camera. The
    camera firmware does not have to do it this way, but it does.
     
    Richard J Kinch, Nov 30, 2007
    #16
  17. Not myself, but in regard to shutter lag, others have:

    http://www.the-digital-picture.com/Reviews/Canon-EOS-40D-Digital-SLR-Camera-Review.aspx
    Tried that, just made things worse. The lag is due to the mirror flip,
    so the curtain choice isn't going to shorten the lag.

    What is needed is an "instrument mode", that leaves the mirror up all the
    time, so the shutter lag is only waiting for the curtain to move.
     
    Richard J Kinch, Nov 30, 2007
    #17
  18. Richard J Kinch

    jean Guest

    Well, Canon did come out with a 20DA for astronomy, would this camera work
    in your application? Maybe if there is enough of a demand they will issue a
    firmware change and come out with a 40DI (for instrument)

    Jean
     
    jean, Dec 1, 2007
    #18
  19. Richard J Kinch

    TH O Guest

    Very interesting. Thanks for posting so much detail.
     
    TH O, Dec 1, 2007
    #19
  20. Hadn't heard of that, but looking at the specs is seems merely to have
    added live preview and mirror lock up to the 20D, which are on the normal
    40D anyway.
    As a trivial firmware feature, it seems like it should just be there. It
    almost exists in the live preview silent mode. Almost, but not quite.
     
    Richard J Kinch, Dec 1, 2007
    #20
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