Stage 2: Using a Tripod

Fun Projects for your LEGO^® MINDSTORMS^® NXT!

Three Stages to Better Photos of LEGO Creations

Stage 2: Using a Tripod

To get beyond the results of the Stage 1 fixes, we need to start taking pictures without using the flash, in order to control the lighting better. In addition, we will want to adjust the camera settings to use a very narrow lens opening (high f-stop number) to get sharper focus and better details. However, the combination of these two means that the camera will require a long exposure (shutter speed) in order to get enough light, and this will require using a tripod to hold the camera steady enough so that the picture will not be blurred.

To be able to use the right camera settings for this stage, your camera must have some degree of manual control over the exposure. See the Camera Requirements for details.

The improvements at this level have mainly to do with getting sharpness and fine detail. If all you want to do is take a single picture of your whole robot to post to the web in a size small enough for a typical web photo, then you probably don't need to bother with this, and the Stage 1 improvements are probably enough. However, if you want to post a high-resolution picture, or crop down to make a close-up (such as in the building instructions on nxtprograms.com), then a tripod will help a lot, as shown in the comparison below, which shows a small portion cropped out of the full-resolution photos.

Canon A570

Nikon D200

Flash

Tripod

You will also notice from this comparison that the SLR takes significantly sharper and cleaner photos than the point and shoot camera. This is not due to a difference in the resolution (although the D200 has 10 Megapixels and the A570 has 7 Megapixels, the zoom was slightly different in these shots, so that the resulting resolution of this cropped portion is almost the same), but rather due to the much larger sensor of an SLR, which results in a significantly better signal-to-noise ratio of the light at the sensor. So there's a reason why not all cameras will fit in your pocket...

Using External Lights for Tripod Photos

It is possible to take a highly detailed photo on a tripod without a flash using only the available light that is already in the room, as in this example:

Nikon D200 on tripod, no flash, normal room lighting only
(f/16 for 15 sec at ISO 100, White Balance Incandescent)

However, there are a couple of problems with using only the room lights. First, the robot is lit mostly from the top, which makes the lower portions hard to see, and there are a lot of shadows. Second, as a practical matter, this photo required a 15 second (!) exposure, which is long enough to be annoying if you have several pictures to take. So, if you have some external lights, such as desk lamps, you can use them to light up the model to improve these problems.

To eliminate as many shadows and dark areas as possible, and to help highlight the edges and details of the parts, it works well to have three external lights: two lighting the model directly from the sides, and the third lighting it mostly from the front, as shown in this arrangement:

Using three desk lamps with incandescent bulbs, arranged as shown above, produces the following photo:

Nikon D200 on tripod, no flash, three incandescent desk lamps (left, right, front)
(f/16 for 1.3 sec at ISO 100, White Balance Incandescent)

Note how the details pop out more, and the underside of the robot is much easier to see. You can further fine-tune the lighting by changing the position of the lights to get more light where you want it.

Using a Single External Light

If you don't have three external lights or don't want to bother setting them all up, here is a trick you can use to get pretty good results with a single external light. If you just set up a single light shining at the robot from one angle, it would only be lit from one side and have huge shadows on the other side. However, using a single desk lamp in addition to the room lights, the exposure in this case will still take 8 seconds to get enough light. So, you can take a single desk lamp, hold it in your hand, and move the light around during the 8 seconds of exposure time to help light up all areas of the robot. In the result below, I slowly panned the light in a half circle from the right side to the front then to the left side. Using this technique, you could even linger a little longer on the dark areas or areas that you want to call attention to in order to light them up a little better.

Nikon D200 on tripod, no flash, one desk lamp panned from right to left
(f/16 for 8 sec at ISO 100, White Balance Incandescent)

The following sections detail the camera settings needed to get good tripod photos, assuming the use of three external lights.

Tripod Settings for Point and Shoot Cameras

Unfortunately, your automatic camera, smart as it is, does not know that it is on a tripod (hmm, what if there was a touch sensor in the tripod mount hole?...). So, if you turn the flash off, then in an attempt to get a short enough shutter speed for non-blurry photos, the camera will make a number of choices that are not what we want for good tripod photos, so we will need to manually change these settings.

First of all, when taking pictures indoors, the camera will normally want to flash, so you have to set the flash to "No Flash".
As in the Stage 1 fixes, you want the camera to be about 3 feet away from the robot, using the optical zoom to make the robot fill the frame. This will be approx a 3x zoom.
To maximize light, the camera will normally try to open the lens all the way (lowest f-stop number). However, we actually want the highest f-stop number that the camera can do in order to get good focus across the whole model (good depth of field). So, we need to manually set the f-stop. On the Canon A570, you can use Aperture Priority mode and set the f-stop to f/8 (as high as allowed).
Given that we set the f-stop to f/8, in order to try to get a shorter shutter speed, the camera will try to boost the ISO sensitivity of the sensor, which will make the picture grainy. To prevent this, we need to set the ISO sensitivity to its lowest value instead of "automatic". For the Canon A570, this is ISO 80.
Depending on your camera and the kind of light bulbs you are using in your external lights, the camera may or may not guess the correct "white balance" for this kind of lighting. To make sure, when using incandescent lights as in this example, set the white balance to "Tungsten" (or "Incandescent" -- they mean the same thing).
With all these settings, the shutter speed will be forced to be long (1/2 sec or more), which is fine on a tripod. However, at this speed, pressing the button to take the picture will bump the camera slightly which will blur the photo. So to get around this, use the self-timer feature of the camera to make a delay between when you press the button and when the picture is taken. The typical use of the self-timer is to allow you time to run around and get in the picture yourself, and a typical delay for this purpose is 10 sec, but if your camera allows a 2 second self-timer delay, then you can use that instead to get it over with faster.

Using these settings on the Canon A570 results in the following photo:

Canon A570 on tripod with three incandescent lights (left, right, and front),
no flash, 3x zoom, Aperture Priority mode at f/8, ISO 80,
White Balance set to Tungsten, 2 second self-timer delay
(the camera chose a shutter speed of 0.6 sec)

Tripod Settings for SLR Cameras

Similar to a point and shoot camera, an SLR camera does not know that is on a tripod, so the automatic choices it would make are not appropriate. We need to manually change the settings as follows:

Make sure you have the flash turned off.
As in the Stage 1 fixes, you want the camera to be about 3 feet away from the robot. On a zoom lens this will result in a focal length of around 50 to 100mm.
To maximize light, the camera will normally try to open the lens all the way (lowest f-stop number). However, we actually want a high f-stop number in order to get good focus across the whole model (good depth of field). So, we need to manually set the f-stop. An f-stop of f/16 is good for this purpose. Many SLR lenses can go even farther (e.g. f/22 or higher), but going this far can actually cause the photo to start losing detail due to diffraction effects. To set the f-stop you will need to choose either Aperture Priority mode or Manual mode.
Given that we set the f-stop to f/16, in order to try to get a shorter shutter speed, the camera will try to boost the ISO sensitivity of the sensor. The Nikon D200 can go all the way up to ISO 1600, which would result in a very grainy looking picture. The sharpest pictures are achieved at the lowest sensitivity settings, which for an SLR should be around ISO 100. To force ISO 100 on the Nikon D200, you need to turn "Auto ISO" off, which is buried down in the camera menus, then make sure the ISO is set to ISO 100.
If you chose Aperture Priority mode, then the camera will choose the shutter speed for you based on the light meter's evaluation of the situation. In my experience, the Nikon D200 will normally underexpose pictures of NXT robots (being conservative to make sure it does not overexpose the white areas), so you can either add Fill Light later in a digital photo editing program, or use the Exposure Compensation control to force a longer exposure by asking for a compensation of something like EV +1. If you choose Manual mode then you can increase the shutter speed yourself until the light meter shows +1 or whatever you find gives the best result. You will need to experiment a bit, so take several shots in a row at different settings to determine the right settings for your situation.
Depending on your camera and the kind of light bulbs you are using in your external lights, the camera may or may not guess the correct "white balance" for this kind of lighting. To make sure, when using incandescent lights as in this example, set the white balance to "Incandescent" (or "Tungsten" -- they mean the same thing).
With all these settings, the shutter speed will be forced to be long (1.6 sec in this case), which is fine on a tripod. However, at this speed, pressing the button to take the picture will bump the camera slightly which will blur the photo. So to get around this, you can use the self-timer feature of the camera to make a delay between when you press the button and when the picture is taken. The typical use of the self-timer is to allow you time to run around and get in the picture yourself, and a typical delay for this purpose is 10 sec, but if your camera allows a 2 second self-timer delay, then you can use that instead to get it over with faster. As an alternative to using the self-timer, you could use a remote shutter release cable if you have one.

Using these settings on the Nikon D200 results in the following photo:

Nikon D200 on tripod with three incandescent lights (left, right, and front),
no flash, 50mm focal length, Aperture Priority mode at f/16, ISO 100,
White Balance set to Incandescent, 2 second self-timer delay,
Fill Light added in photo editing program
(the camera chose a shutter speed of 1.6 sec)

Light Bulbs and White Balance

When using external lights, getting the "white balance" right can be a little tricky, since the color of the light given off by various light bulbs differ. With your camera's white balance set to automatic, it may or may not make a good guess on the white balance. Errors in the white balance can be corrected somewhat using Picasa's Neutral Color Picker, but only to a point. Further corrections could be made in a more advanced program such as Adobe Photoshop, especially if you take your photos in "RAW" format rather than JPEG, but an easier solution if you have a lot of photos to take is to use daylight fluorescent light bulbs, which are designed to give off a precise light color that imitates full-spectrum sunlight.

The following sequence of photos shows a progression of photos with increasingly more accurate white balance.

Incandescent lights, White Balance "Automatic"

Incandescent lights, White Balance "Incandescent"

Incandescent lights, White Balance "Incandescent",
Neutral Color set on NXT brick in Picasa

Daylight/5000k Florescent Lights, White Balance "5000k"

Note that in the last picture with the daylight florescent lights the carpet color looks much greener. Both this picture and the incandescent photo above it actually have a "correct" white balance, the difference just comes from the actual appearance under the different light bulbs. My carpet really does look brownish at night under incandescent lights and a little greenish during the day when daylight shines on it. The important part is that the colors in the robot are correct. The whites are white, the grays are gray, and the blacks are pure black. Note that the last picture is slightly the best in this regard (look at the tires).

Summary of Tripod Photo Settings

Point & Shoot

SLR

Three external incandescent lights (left, right, front)

No Flash

Camera about 3 feet from robot

About 3x zoom

Focal length 50-100mm

Aperture Priority mode at f/8

Aperture Priority mode at f/16

Sensitivity manual at ISO 80

Auto ISO off, ISO 100

White Balance "Tungsten"

White Balance "Incandescent"

Self-timer with 2 second delay

Use digital photo editing software to adjust the lighting afterwards if necessary

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