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Author Topic: Photography technicalities  (Read 303 times)

PeterC

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Photography technicalities
« on: 21 December 2016, 17:55:28 »
Peter's set-up
  • I used my (wife's) current camera: Canon IXUS 80 IS (8MP) - also known as: PowerShot SD1100 IS (US), IXY DIGITAL 20 IS (Japan) - Firmware 101a, Focal length (35mm equiv.): 38 - 114 mm
  • The rig (see photographs attached below):
    • one cheap tripod (Hama Star 75 from Amazon)
    • central rod extended fully
    • the 2 "front" legs extended by one section
    • the "back" leg fully extended, and held down by a string/chain to 2 hand training weights (from Tesco) tied together
    • if necessary, using book(s) under the pair of weights to adjust the height of the camera at the other end
    • 2 hand training weights for each front leg (1 behind to stop it moving, 1 wedged in front to damp vibrations - important if using a delay timer)
    • 2 * 24 inch steel rules to act as weights on the map
    • small double level (sold for caravan levelling) - to level the camera (taking into account that weight of the level affects the levelling)
    • large card or paper ruled for guidelines stuck to floor so one set of lines are parallel to the camera - to help align the map as I move it for each shot
    • the quick release plate on the tripod was very useful, as I could do things with the camera without affecting the rig
    • attach a long USB lead to the camera - to be used for transferring JPG images when experimenting (so the plate could stay attached to the camera), and for the shutter release when using CHDK (see below about DNG/RAW format)
    • (the rig extends behind the front legs by about 90 cm but I can, if necessary, shorten the back leg and hence this dimension)
    • adjusted so the end result is the camera is 19-23 cm above the map, and the reach from front legs to camera is 88 cm - this is helpful so that I can photograph large maps
    • (it is worth setting up most of the camera settings before attaching the camera on its quick release plate to the tripod)
  • The settings on the camera are:
    • (the default Point and Shoot settings on the camera mean it is losing preciseness, so it is worth exploring the settings: for that we need to understand a bit about photography, and what is possible with my camera - where I discover things I will have added them below)
    • to vary some things (exposure compensation, but could also vary white balance and My Colors) we need to use Manual Mode (Func Set - changed from our default of Auto)
    • experiment with exposure compensation (can vary from -2 to +2 : +1 2/3 seems a good starting point) to get a well lit image (Func Set - default is not relevant in Auto mode)
    • when experimenting, checking the histogram (eg in irfanview it is Shift H) of the image can show what the minimum and maximum brightness are - we are aiming for a good spread (0-255)
    • max pixels: L (8M pixels) (Func Set - changed from our default of M2) - best resolution
    • AutoFocus (AF) Frame: Center (Menu - changed from our default of Face Detect) - uses the centre of the frame for the autofocus
    • compression: Superfine - S (Func Set - left as our default) - best quality setting for JPGs
    • Image Stabilizer (IS) Mode: Continuous (Menu - left as our default) - this just means it applies to the LCD all the time
    • each time we start taking shots we need to change, or at least check:
      • ISO ("film speed"): 80 (top button - have to set again after turning off/on) - gives least noise, but needs longest exposure
      • flash: Off (right button - have to set again after turning off/on) - keeps lighting as even as possible
      • macro mode: On (left button - have to set again after turning off/on)(without Macro Normal Focusing Range is 30 cm – infinity; with Macro it is 3 – 50 cm)
      • self-timer (only needed if we do not have a shutter release cable): 10 seconds if rig is very bouncy (bottom button p66 - have to set again after turning off/on)
    • White Balance, digital Zoom, AF Lock, Metering method etc left as default
    • (if necessary, and photographing a map in just one shot, use the optical Zoom to get the area wanted)
    • press button halfway (or turn on remote power) to focus, then full down (or turn off remote power (if set, the timer then does its 2 or 10 second delay)
  • To use the Canon Hacker's Development Kit (CHDK) (also see the CHDK manual):
    • (Note: do not do this when testing for exposure settings, as it is not necessary, and it prevents downloading images to a computer)
    • put the SD card with CHDK into the camera
    • set to Playback mode, turn on
    • (every time we turn ON) set the camera to temporarily use CHDK: Menu, (Up) Firmware Update, OK
    • to enter the Alt Menu, with its special keys, press the Print button (here known as ALT) for less than a half second
    • special key: Menu leads to the CHDK Menu
    • special key: Display (which normally turns on the screen display when shooting) now goes back one menu
    • to save images in DNG/RAW (as well as JPEG), ALT MENU, RAW Parameters; check the Save RAW box, and tweak any other settings we want (using RAW is too difficult for me)
    • (note that the print button flashes blue during the RAW save process)
    • to enable USB remote operation, go to the CHDK Settings/ Remote parameters menu and select
      • enable Remote ON
      • switch type: OnePush   (ON: "half-press", OFF "full-press" )
      • control mode: Normal (half press: focus, set exposure and flash settings; full press: take the actual photograph.
    • ensure Disable Overrides is YES, and Disable Overrides on Startup is enabled
    • it would be better to use a smaller aperture to get better focus, but on this camera we cannot override the automatic aperture of f2.8-4.8
    • use the Print button (ALT) again to exit <ALT> mode - in order to take photos normally!
    • (Note: When entering numeric values in menu item fields, the zoom lever can be used to move left and right over digits; and the left/right buttons change the number)
    • CHDK settings persist, but to reset all CHDK option to the default values used when CHDK starts for the first time go to the CHDK Settings/ Reset Options to Default
    • to turn off CHDK the easiest way is just to turn the camera off and then on again
    • My camera, needed Acid to find the firmware version
    • CHDK loaded easily onto a spare SD card, and I could readily start it up in the camera without any permanent effect
    • Note that, if we did generate them, DNG files cannot be seen or transferred over the camera's USB connection, but can be by taking the SD card out of the camera and putting it into a card reader plugged into the computer
  • The process:
    • once the rig and camera is set up we try not to touch or move it, and move only the map - in a regular way oriented in the same way

Test Examples(Hint: move the mouse and you will see a spyglass comparing the whole and the stitched versions of the same map - there is a lot more you can do in this prototype mapping system, but for this purpose it is just to show the difference between the two images)

Useful references:
« Last Edit: 11 January 2017, 15:36:54 by PeterC »

 

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