HDR Bracket Shooting with the Nintendo DS

Transcription

1 HDR Bracket Shooting with the Nintendo DS Assuming you have constructed or obtained the appropriate cable to interface your camera to the DS, we can begin shooting HDR sequences. The DS software will make a few assumptions about the settings on your camera. The camera will be set to Bulb mode and Manual aperture. The DS will control the exposure length by a variable length closure of the cameraʼs manual shutter port. The camera should be set to manual focus. This is not mandatory, though if auto focus is used, a suitable amount of time should be added to each shot to make sure focus has been found. We never use autofocus in shooting HDRʼs, itʼs simply good practice to know where the lens is focused, and that each shot has consistent settings. In our time spent in film sets observing some great DOPʼs, weʼve never heard anyone say rolling...autofocusing...and action! Upon launching the bracket software, weʼll see these two screens on the DS. The first is the main settings. By pressing START weʼll see the panorama calculator. The screen is mainly used to configure an attached pano motor, however it might be useful if one is doing manual camera moves. If shooting with an older camera, or slow memory card, setting the memory speed slider may be necessary. Most cameras can handle continuous shooting, though Canon Rebels, the Sigma SD-14, or cards like the Eye-fi might need a little cushion. If you see that the DS is triggering shots while the camera is still saving the previous picture, add a little delay by moving the slider left.

2 Set the desired mirror lockup delay. This is a subjective setting, although intended to wait for internal camera vibrations to settle, it can be adjusted to compensate for the general stability of the tripod and head as well. We like to travel with the lightest carbon-fiber tripod, so we adjust the mirror lockup delay to account for a greater amount of vibration. This setting does not tell the camera to use Mirror Lockup. ML must be enabled or disabled in your cameraʼs menu functions before shooting. Many cameras do not have a reflex mirror, so the setting is not needed. If no ML is used, the setting should be adjusted to 0.00 seconds. In-camera noise reduction is a mixed blessing. It allows new cameras to shoot at high ISO and low light, but requires a lot of processing power. The 5D Mark II, for example, will take twice the exposure time to shoot an image, not noticeable for quick shots, but a five second exposure takes ten seconds to shoot and process before saving. The noise-reduction setting simply informs the bracketing program if youʼve turned on or off NR functions in your camera. It does not change the setting itself, it is merely a way to tell the DS that it needs to take extra time after each exposure to allow the camera to compute the NR filter. Merging multiple images ameliorates the effect of sensor noise, so you may wish to try turning it off in order to speed up HDR shooting in dark settings. the difference between a five minute shot and a ten minute delay to compute NR for a five minute shot is significant, and some hold the opinion that there are more controllable ways to deal with noise; taking a single dark-frame shot per session, for example, to be subtracted downstream in the processing workflow.

3 A number of radio buttons act as a quick way to better control shooting. The MT setting offers the option to stop between each shot an await a button press before continuing. In this example, Highway 395 is a few meters in front of the camera. The shots were triggered manually when a long-enough gap between cars occurred. For longer shots, my timing isnʼt always perfect. The 2X button takes a second insurance shot for every exposure to increase the chance of success. The REV function reverses the order of the shots, switching from fastest-to-slowest to slowest-to-fastest. This was added when it was noticed that shots after sunset can be slightly different depending on the shot order, as the brightest images became darker as the twilight progressed. The WU setting fires a throw-away shot at the beginning of a bracket sequence. This is mainly used during intervalometer time-lapse shots, when the camera might enter sleep-mode. The SS setting simply turns off the display backlight during a shoot, to save battery life. The DS is designed to be used for several hours before charging, so it is usually moot. The PM setting starts a motor-controlled panorama, more info can be found in a separate document.

4 The Stop Steps setting is changed by touching the number inside the ring. It is currently programmed to switch between 3, 5, 7, and 9 stops of bracketed exposures, with an even number above and below the metered shot. Itʼs the photographerʼs choice, the amount of bracketing needed hinges on the physical conditions of the scene, although I have also found that metering a scene is sometimes inaccurate, and adding more stops of padding allows for choosing the correctly exposed images during processing after the shoot. It is not uncommon to find one or two extra shots of nearly black or white-out images. Below the steps function is the Stop Interval setting. It can currently be stepped between 1/3, 1 and 2 stops of stepping between shots. The effect of this setting is a trade off between the number of exposures and the amount of time it will take to complete the sequence. The effect can be most easily judged by watching the arrowheads and tick marks on the upper screen, these represent the actual shots to be taken during a shot sequence.

5 The slider function across the top of the lower screen quickly sets the metered exposure or middle shot of the HDR sequence. This exposure should generally mark what an ideal non-bracketed, non-hdr imageʼs shutter speed would be set to. The DS touch-screen pen is used to slide the diamond across the scale, and the rest of the sequence will automatically adjust around this setting. In a pinch, when the DS pen is misplaced, this setting can be changed with a finger and a little patience. The test buttons can be used to judge if the exposure outcome is as desired. If the settings are made and you know youʼll be moving the camera, tripod, or maybe rotating the rig for a panorama, the Padlock setting is used to ensure that the sequence doesnʼt accidentally change. Weʼve use the DS to document dozens of props and objects on a movie set, for example, and use the padlock to make all of the sequences consistent to one another.

6 The Planned readout confirms the number of images to be taken. The Sequence Duration readout estimates how long a HDR bracket sequence will take to complete. It acts as a fast way to see the effects of all of the various settings on exposure time, and good way to tell if using things like 2X insurance will simply take too long for a given situation. The Walk Away delay setting determines how much time youʼll have to hang the DS on the tripod and walk away so that you donʼt interfere with the shoot by bumping the tripod, or moving on flexible floors.

7 The Intervalometer can be used to take continuous HDR time-lapse sequences, although Iʼve yet to find an efficient means of processing the number of images that result from shooting so many exposures. For a more traditional intervalometer, use the standalone interval shooter DS program, which allows for rapid single setting sequences. Shooting To begin shooting, hold the left and right shoulder triggers on the back of the DS and place the DS in a stable location before stepping back. If you hang the DS from the tripod using the wrist strap, watch out for pendulum motion that can have a subtle effect on the image quality. The Current readout will tell you what shot is being taken, i.e. 1/2 second etc.

8 If you are using the intervalometer, the Interval Remaining readout describes the wait before the next sequence begins, otherwise the Sequence Remaining display offers up the remaining amount of time before the current sequence finishes. Keep in mind that these readings do not update during a shot, because the DSʼ CPU is being used to carefully control shot timing. Since the longest shot is usually the last, and the timer doesnʼt update during this shot, there might be a shorter waiting period than displayed. The Remaining readout simply shows how many more shots need to be taken before an HDR sequence is finished. When it reaches zero, a vocal announcement indicates that the camera is ready to move on to the next position. We tried to make it as loud as possible, though the DS has limited speaker size and volume.

9 Once you take your haul back to the office for processing, youʼll be ready to process the images into HDR, and weʼll discuss some DS specific techniques in another document. Hereʼs some crazy over-processed tone-mapped good/badness taken with the Nintendo DS Phat and an Olympus E-P1 with 17mm pancake. I set the tripod and walked away as the DS shot a seven image bracket, while I discussed the niceties of fighter jet restoration with a technician at the Boeing factory in Everett, Washington. If you wish to modify the software to suit your own needs or establish presets for a particular camera, have a go at the included source code.