ALZO Digital

IMAGING TENT APPLICATION GUIDE

HOW TO - PRODUCE A PRODUCT IMAGE
WITH A PURE WHITE BACKGROUND

There are three requirements to achieve a pure white background when photographing products in a tent.

1. Adjusting the lights relative to the subject

2. Setting the correct camera mode, aperture, metering and exposure

3. Image editing with software.

4. Eliminating under object shadow

1. Adjusting the lights relative to the subject

The objective of the position of the lights relative to the subject is to strongly illuminate the background while casting less light on the subject.

This is accomplished by positioning the lights towards the rear of the tent pointing at the background and moving the subject forward in the tent (see diagram on right).. You will need to experiment with the position of the subject, for if you move it too far forward in the tent with the cover removed, your product will not get sufficient illumination and it will be underexposed.

If your lights are on light stands and the tent is on a table, the stands will be placed against the front of the table. If you move the tent to one side of the table or if your working table is small, you can easily position one or more of the lights towards the rear of the tent. The tent will be positioned with the front protruding out over the edge of the table, and the subject will then be placed in the tent close to the front edge of the table.

The camera on a tripod should be a few feet in front of the tent which will allow you to zoom in on the subject. A camera too close to the subject will distort the shape of the subject.

Strong background illumination can be accomplished with a 2 light kit but it is better with a 3 light kit where the third light is a boom mounted overhead light. The overhead light should be tilted toward the background.

Correct setup - subject forward - lights back

A third overhead light is very important when photographing tall objects in a tent as 2 lights may not be sufficient to illuminate the top of the background, and the images will have a gray band on the top. Also, more light produces better results

HOW MUCH LIGHT IS REQUIRED?

The more light the better. Low light levels in a tent will require very long exposures and will increase the objectionable digital noise in the images. We recommend at least 500 watts of light in a 28" tent and at least 1000 watts in a 48" tent. Remember the tent walls reduce the light entering the tent and therefore strong illumination is a requirement.

2. Setting the correct camera mode, aperture, metering and exposure

CAMERA MODE SELECTION:

First turn OFF the flash
and FORGET AUTO MODE:

You will not be able to achieve a pure white background or correct color or properly expose the subject setting your camera to AUTO mode.  This image of a wood carved head was shot with a Fuji S7000 in auto mode and is typical of most digital cameras AUTO MODE.

APERTURE SETTING:

We recommend setting your camera to "aperture priority" mode or manual exposure. If your camera does not have an "aperture priority" mode or manual exposure mode you should get a better camera. An SLR is not required. A Fuji S5200 or S9000 is a perfect low cost digital camera for tent imaging. Some cameras have a P mode that will allow you to set most of the parameters discussed below. With your camera in "aperture priority" mode or manual exposure you can set the aperture to a small opening like f-8 or f-11 thereby increasing depth of focus. Greater depth of focus will produce much sharper images. Your camera must be mounted on a sturdy tripod as your exposure time will most likely be long. We recommend using the auto timer in the camera as this will allow you to have hands-off the camera during long exposures. Note: the Fuji S9000 has a mechanical shutter release option which is perfect for long exposures. If you don't want long exposures then you need much brighter lights.

WHITE BALANCE SETTING:

Light has a wide variance in color temperature which will effect the overall color tint of a digital image. Digital Cameras provide adjustability to compensate for variation in the color of light and this function is referred to as "White Balance".

The optimal white balance setting is "captured" by the camera and is typically available on many current issue 4-8 mpix digital cameras. This feature allows you to "custom set" the white balance using a "white card" placed in front of the camera. This feature is available on the FUJI S5200 and the FUJI S9000 cameras and is frequently referred to as "custom" white balance. This option will provide near perfect color reproduction when using artificial lighting. Study your camera manual for procedures on setting "custom" white balance (NIKON refers to this feature as pre-set white balance). If your camera does not provide "captured" or "custom" white balance, you should upgrade your camera.

This image of the head was shot with the Fuji S7000 in Aperture Priority mode, aperture set to f 8, shutter speed was 1/40 sec. with a Custom White Balance "captured" from the inside tent wall. Notice the difference from AUTO MODE above.

In practice we have found that when capturing a white balance, aiming the camera at the surface of the tent where the light is very strong will produce the most accurate white balance. Using a white card (as described in many camera manuals) is the second best option, and we recommend holding the card very close to the light source as more light in the camera produces more accurate white balance.

The second choice is selecting a "preset" white balance. Study your camera manual for procedures on setting a "preset" white balance.  Use "interior", "incandescent" or "Tungsten" for continuous HOT light or Quartz Halogen light kits. Many cameras today provide several presets for florescent lighting. If your camera does not provide several florescent presets then try "daylight" white balance with ALZO Cool lights.

Using a "pre-set" white balance may not reproduce perfect color but will always be consistent when using a specific light source. A consistent color shift is easy to correct in software, and once you get the correction parameters set, you will use this adjustment on every image and get excellent results.

METERING OR PHOTOMETRY SETTING:

Many cameras provide options for exposure metering and although they may vary in naming they are; Average, Center Weighted, Spot or Multi-Spot. If your camera metering provides these options we recommend using either center weighted or spot. Spot metering typically produces the most accurate exposure of most objects because the meter is only measuring the light on the subject and not the background.  If your subject has high contrast areas i.e. silver on black, spot metering is not recommended, use Center Weighted.

EXPOSURE COMPENSATION SETTING:

This is a very important camera setting to master. Setting the correct exposure compensation will properly expose the subject and white-out the background. The exposure compensation control (the +- symbol shown) should be set to +.7 to +2 and this setting is dependant on the lightness of the subject and the mode of light metering that the camera is set to. You will need to experiment with this setting and you may want to take several shots with different settings to assure that you get the optimal subject exposure. Study your camera manual for procedures on setting a exposure compensation.

This image of the head was shot with the Fuji S7000 in Aperture Priority mode, aperture set to f 8, with a custom white balance and Exposure Compensation set to +1.7. The camera selected shutter speed at 1/10 sec. Camera was on a tripod.

Medium density to dark subjects are the easiest to expose for a white-out background, whereas very light subjects are very difficult and always require more image editing in software.

Although ADOBE Photoshop CS is the defacto standard image editing software application, we know for most product imaging tasks it is overkill, expensive and not the best choice. Many digital cameras include an image editing application with the camera and this product will, in most cases, have all the power needed. If your camera did not come with image editing software, we recommend either Corel Paint Shop Pro, Ulead Photoimpact, Arcsoft Photoimpression, Microsoft Digital Image Suit and others that sell for under $100. All of these products include very robust sophisticated features.

CONSIDER YOUR "WORK FLOW"

It is important to consider "work flow" when using image editing software for you will be accomplishing several tasks and the logical order is important to master. A typical editing work flow may include:

• Transferring images from camera to computer.
• Naming and filing images
• Cropping and or rotating
• Contrast adjustment
• Background selection and erasing
• Resizing
• Backing up images.

This list may sound like a lot of work when you have hundreds of products to image but some of these tasks are automated in some image editing software products.

CONTRAST, BACKGROUND SELECTION & ERASING

The Contrast Adjustment step and the Background Selection and Erasing step are the operations that will produce the total white-out background. With most images a simple contrast boost will completely white-out the background and will also improve the look of the subject and liven up the colors. All products photographed in a tent require a contrast/brightness boost to make them look better on a computer screen.

This image of the head was shot with the Fuji S7000 in Aperture Priority mode, aperture set to f 8, shutter speed 1/10 sec with a Custom White Balance and Exposure Compensation set to +1.7. Contrast and Brightness were increased 15% using Corel Paint Shop Pro. Notice that the background is almost gone.

If the contrast boost does not white-out the background completely, then you will need to use either use a paint brush (color pure white) to clean up the background or you can use a "selection tool" to select the background and then replace it with pure white. Study the software manual or follow a tutorial for "paint brush", "area selection" methods and "color replacement". Below is our final cropped head.

1. Use of a clear riser platform
2. Bottom illumination of the tent

A clear riser platform (as shown) placed inside tent is the easiest solution. This platform raises the subject above the tent floor and eliminates the shadow.

Bottom illuminating a tent requires using a glass table and placing a third (or fourth) light under the table and under the tent. The difficulty with this approach is supporting the light under the table as tables can have obstructing legs and supports