digital camera live preview

see also:
- a review on Canon's live preview with WiFi applications:
  - http://www.sportsshooter.com/news/1752
- a review on live preview for astrophotography using the Canon 40D:
  - http://www.cameralabs.com:80/reviews/Canon_EOS_40D/live_view_astro-photography.shtml
- for those who do not have live preview (ie. don't own the E330, etc) but would like one:
  - Zigview live preview LCD attachment to viewfinder - ~$US299
- remote control of cameras

NB. this was written when Live View had only just started becoming mainstream in dSLRs in 2007

Introduction:

Live preview is the technology in most current digital cameras that allows you to compose your image on an LCD screen without looking through the viewfinder.
Live preview has a number of significant benefits over optical viewfinders including:
- ability to compose without having your eye against the camera:
  - if the LCD screen is tiltable, this allows camera to be placed on the ground or above your head or on a pole, or just on a tripod without you having to bend down and squint through the viewfinder in an awkward position.
  - if the LCD screen is not tiltable you are left with just using it in front of your face, although the newer LCD screens with almost 180 degree viewing angle may allow more versatility.
  - if the LCD screen is rotatable, you can see what you are taking for self-portraits.
- if the camera allows you to magnify the preview image, then more accurate manual focus becomes possible.
  - this capability is quite critical for macrophotography, tilt-shift lens photography & when AF is not possible.
- if the image is derived from the main picture-taking sensor then:
  - true depth of field assessment is possible assuming you can stop down the aperture.
  - 100% field of view of image is likely to be possible instead of the usual 90-95% with optical viewfinders.
- the camera may optimise the LCD image to brighten it for dark scenes or dark filters which may be otherwise difficult in an optical viewfinder (Olympus but not Canon as no Live Boost mode)
  - photography of stars - it may be possible to more readily focus on the brighter stars if aperture wider than f/4
  - infrared opaque filters may still be able to be composed as long as the sensor does not have a strong IR block filter
  - night scenes
- the camera may provide overlay functions to assist in composition:
  - grid lines to assist in ensuring your composition is level or straight.
- may display effects of selected exposure and white balance to give a true WYSIWYG display:
  - most non-SLRs;
  - Canon EOS 1D Mark III with exposure simulation set to on or during DOF preview;
  - Olympus E410/510 but not E330.
- remote Live preview may be possible with some cameras to allow image to be sent live to another device such as TV, computer or PDA - eg. Canon 1D Mark III with WiFi option
Live Preview also has disadvantages:
- holding the camera away from the face increases camera shake
  - although if it is being used for MF, then once focus is achieved, one can revert to optical viewfinder as long as you don't move the camera closer or further from the subject.
- prolonged use of live preview from the picture-taking sensor may increase noise in subsequent images by heating the sensor
  - some SLR cameras limit live preview to 15secs or so (eg. Fuji, Canon 20Da)
- may not display effects of selected exposure and white balance (but then neither will optical viewfinder)
  - eg. Olympus E330
- auto-focus and TTL flash are THE main issues:
  - if the preview is from the picture-taking sensor on a dSLR, to AF, one must either:
    - use AF technology associated with the picture-taking sensor but this relies on less efficient contrast detection systems which currently are more problematic (ie. slow) in low light or low contrast situations
      - non-SLRs such as the Olympus C8080WZ
      - Nikon D300, Nikon D3x - can select an part of image to focus on in “tripod mode”
      - Panasonic Lumix DMC-L10 (also has face detection AF, intelligent ISO mode and a rotating LCD screen)
    - if it is an SLR it may not allow AF during Live Preview mode:
      - Canon EOS 1D Mark III:
        
        for TTL flash, mirror must drop down for pre-flash metering.
        
        otherwise metering and WB is via the picture-taking sensor thus mirror can remain locked during exposures for quieter shooting.
        
        see http://www.robgalbraith.com/public_files/Canon_EOS-1D_Mark_III_White_Paper.pdf
    - otherwise, it must drop the mirror down temporarily to allow light to the main AF sensors to focus and then move the mirror back up again to re-display the live preview
      - Olympus E series SLR
      - Canon 40D
      - Nikon D300, Nikon D3x
      - see digital cameras and focusing
  - if the preview is from a secondary sensor (“Live Mode A” in Four Thirds terminology):
    - camera must have a unique design which splits light coming to the viewfinder and redirect to the secondary sensor (as in the Olympus E 330 SLR live mode A) but although this gives the most responsive AF in live preview it has some disadvantages:
      - image may not be 100% view
      - depth of field assessment not as accurate
      - optical viewfinder view darker
      - may not allow live magnified view or grid lines (as in Olympus E330)
    - Sony has decided to venture into this niche market in 2008 with their a300 and a350 dSLRs and they have gone one step further on the Olympus E330 by incorporating a 2.5-3.5EV IS.
- does not work for imaging Xrays on a screen lit by flourescent lighting as the horizontal banding artefact makes it near impossible to use. I suspect this may be an issue for other older technology flourescent lighting situations but new flourescent bulbs do not seem to be an issue.

How easy is Live Preview implemented?

mirrorless camera systems:
- these cameras have the easiest live view as this is what they use all the time, and there is no need to worry about a mirror
Olympus E330:
- mid-2006
- has a dedicated live preview (LP) button
- live preview is automatically displayed after exposure taken (after the taken image is temporarily displayed)
- has a dedicated button to switch from Live Mode A and Live Mode B via the control dial.
- can set Live Boost on for viewing darker scenes or with IR filters in place
- the ONLY dSLR (except Panasonic) with separate Live Mode A
  - thus has the easiest Live Mode A with real time AF as it is
- the ONLY dSLR with live preview on a flip out LCD screen for easy use at ground or waist level for discrete candid photos (several have a rotatable swing-out screen but these sit beside the camera so not as discrete as the E330 flip out but have the advantage of use for self-portraits)
Olympus E410/510:
- mid-2007
- has a dedicated live preview button
- must press the AF button to drop mirror down transiently for AF
- can set Live Boost on for viewing darker scenes or with IR filters in place
- no live mode A, no real time AF
- can use mirror lockup with Live Preview and you can even specify how many seconds mirror is locked up prior to exposure starting (see Antishock setting on menu)
Olympus E-3:
- Nov 2007
- similar live preview features to the E510 but with a swivel out & rotatable LCD screen in a pro body.
Canon 1DMIII/40D:
- mid-2007
- can program the SET button to go into Live preview mode via menu wrench II : Live View function settings = enable.
- clumsy AF on the 1DMIII as must hit SET button to go out of LP then activate AF then hit SET button to return to LP.
- 40D allows AF as with Olympus E410/510;
- no Live Boost so NOT suitable for IR filters or dim astro targets (eg. total lunar eclipse at f/5.6)
- no live mode A, no real time AF
- use of simultaneous mirror lockup cumbersome:
  - if mirror lockup enabled C.Fn III-15-1, must go out of Live Preview first for it to function, then press shutter button once to activate mirror lockup, then press shutter button again to take exposure.
    - if using TC-80N3 Remote Controller with interval timer, set number of photos to twice the number you need in this mode but be aware that actual interval will be double that selected on the remote.
    - don't forget to set the interval to allow for camera to get back to shutter ready (and if using dark frame noise reduction for long exposures, this includes a 2nd exposure duration!)
  - if mirror lockup enabled C.Fn III-15-2 which means mirror lockup de-activated by SET button, this works best in Live Preview if using continuous drive mode.
- even worse, if you want to use mirror lockup and Live preview and Bulb exposure and self-timer, then it is only one shutter button press, not two as for usual mirror lockup, thus you have to do this:
  - enable Live Preview to work using the SET button via wrench II on menu.
  - set C.Fn III-15-1 to enable mirror lockup
  - set mode to BULB
  - set drive mode to self timer
  - press SET button to enter Live Preview, compose and focus as usual
  - press SET button again to exit Live Preview
  - press shutter button and HOLD button down to activate mirror lockup AND take exposure - THIS is different to usual mirror lockup mode as you don't press shutter button down and release to activate mirror lockup prior to taking exposure!
  - this in reality forces you to use a TC-80N3 Remote Controller or RS-80N3 Remote Switch in Bulb mode and there is no simple IR remote to do this as there is with Olympus.
  - if using the camera's 10sec self timer and you want to take a 60sec BULB exposure using the TC-80N3, set the TC-80N3 to LONG mode and 1min 10sec to allow for the camera's 10sec self timer mode, then press Start.
- in addition, if you want to use mirror lockup in continuous drive mode you must use C.Fn III-15-2 setting
Nikon D300/D3/D700:
- late 2007
- clumsy activation of live preview:
  - use mode dial to set LP mode THEN press shutter release to put mirror up for LP but only for one shot, must do this again for each shot!
  - cannot use other modes on mode dial at same time as Live preview ie. self timer, mirror lock, sequential shooting
  - thus cannot even use self timer simultaneously with mirror lockup - what are these guys thinking about?
- allows AF as with Olympus E410/510 but:
  - LP returns when you take finger off the AF-ON button & not automatically when AF is attained - another clumsy feature
  - has an added advantage of real time AF using contrast detection via main sensor BUT slow AF AND activating this mode requires setting Live Mode in the menu to “tripod” mode.
- perhaps even higher magnification possible than with other dSLRs given the higher resolution VGA LCD screen, but 10x magnification of the others seems adequate for accurate manual focus.
- no Live Boost so NOT suitable for IR filters or dim astro targets (eg. total lunar eclipse at f/5.6)
- more jerky than Canon - refresh rate 15fps instead of Canon's 30fps.
Panasonic Lumix DMC-L10:
- early 2008
- similar to Olympus E510 but:
  - no sensor based image stabiliser (optical IS in lenses instead)
  - more expensive
  - has contrast-detection AF in live preview with:
    - face detection AF
    - intelligent ISO mode
    - rotating LCD screen
Sony a300 and a350:
- early 2008
- similar design to the Olympus E330 in that uses 2nd sensor to give “live mode A fast AF” plus a tiltable LCD screen and adds a 2.5-3.5EV IS.
- but instead of splitting the light beam to go to this 2nd sensor as in the E330 which made its optical viewfinder dimmer, the Sony approach uses a tiltable mirror within the viewfinder which in Live View mode tilts so the light beam is directed at the sensor instead of the eye.
- this means you can't use the optical viewfinder simultaneously and the viewfinder is a bit tunnel-like.