BACK FOCUS SETTINGS
November 19, 2001 by: Lensmith
For a variety of reasons, your backfocus can be messed up. Anything from using someone elses camera to swapping out a lens. I've had to adjust my backfocus in the field several times.
Put the camera on sticks. Zoom in and focus on something really far away. Tree branches, a fence, anything with nice fine/thin lines. I also like to use my neutral density filters to make the focus point as critical as possible. Once you've zoomed in and focused, zoom back out wide. If you're picture is soft, you have to loosen (but don't remove!) the set screw at the back of your lens and then twisting that ring, not the normal focus section of your lens, adjust your focus. Again, look at the wide shot in your viewfinder and find nice fine lines in the picture to help you set a good focus. Once you have the picture focused, tighten that set screw you loosened. Be gentle. It's easy to move that ring out of focus a bit when you are re-tightening the screw. Zoom back in to the same point you focused on before. Focus and pull wide again. Your picture "should" be nice and crisp. If not, repeat the procedure again. Sometimes you have to do it twice to "be sure". You'll be surprised how easy it really is to set your own back-focus.
It's a lot easier on the eyes to do this in the engineering shop with a chart and nice big color monitor. The problems I've had with some shop-set back-focus is most shops aren't very big so they set the chart up only ten feet away or less. With the chart that close, you may still end up with a "soft" wide shot when you get back to the field.
Remember, the further away that chart or point of focus is, the better you'll be when setting your back-focus on the lens.
November 19, 2001 by: Dinosaur
What Lensmith does works in a pinch, but for better accuracy I would recommend setting backfocus in a lower light setting. Outdoors your depth of field may be too great for an accurate backfocus adjustment. Use the same proceedure that Lenssmith outlined, but work in a setting where your iris is nearly wide open. If you don't have a resolution chart you can use a full page newspaper ad with lots of detailed vertical and horizontal lines hung at about 20 feet from the camera.
Try to use a decent color monitor when making the adjustment so that you are seeing both chrominance (chroma) and lumeinence (brightness). By using the viewfinder for adjustment reference, you can be fooled by a misadjusted viewfinder diopter lens.
WHITE BALANCE TIPS
MORE TO KNOW
[11/24/03] From: Eric J. Smith, Director/Director of Photography, Puritan Films
I rarely use anything but my "Preset" white balance. Preset defaults your white balance to 3200 Kelvin degrees (except on some newer cameras where there is an ENG menu setting to switch between 3200 and 5600 Kelvin degrees). It is as if you were shooting color film, where you don't have a white balance button, and must use filters. This usually takes some practice to train your eyes what different color temperatures your light sources are (unless you want to buy a $1,500 color temperature meter).
What is happening when you white balance is the camera's circuits are electronically reading the voltages from the red, green, and blue circuits, and balancing them out to produce a "white" signal. If you're in a bar with blue neon signs blaring, the blue circuit will have a higher voltage, and when you white balance, it desaturates the amount of blue in the picture. Thus you lose much of the rich blue ambient light.
I try to stay in Preset as often as I can, and make my key light source a 3200 Kelvin degree or slightly warmer source. Be careful of other light sources infringing on your key light though. I like the look of various color temperature sources though.
There are other ways to make your colors richer that are much easier and a little safer. Here's a few:
1. Slightly decrease your exposure. This will knock down the luminance value, and increase the saturation. Auto Iris is usually the biggest culprit of desaturated images.
2. Flag off any stray light into your lens. Look at your lens and pass your hand in front of it. If a shadow passes over the glass, then your lens is being "flared". This decreases color contrast.
3. When shooting outside in daylight, use a Polarizer. A Polarizer cuts down ambient stray light from the sky that decreases color saturation.
4. Stay away from Fluorescent and Mercury Vapor lights. These lights do not put out a full spectrum light. They predominately produce a spiked green and red light, respectively. Without getting technical, a camera that is white balanced to these lights will either have desaturated colors or will have noisy (grainy) signals.
I'M IN THE BOOK
10/3/02 from: Bob Mark:
There have been a lot of suggestions about white balancing to achieve a warmer look. An easy way to do this is to use a color gel sample book. My favorite is the "Jungle Book". You can use color correction blue (CTB) in 1/8, 1/4 or 1/2. Just place it over your lens and white balance on a regular flat white card.
If you are under the influence of florescent lights try combining a 1/4 blue with a 1/8 green gel at the same time and then white balance. Florescent light may have a green spike and by adding the green gel you can adjust for that.
Experiment with various gels strengths and combos to get the most pleasing color. Most of all, be sure your monitor is set up correctly before white balancing! Remember, too much color shift and your subjects will look like naval oranges!
THE SUN'S COMING UP ROSES...
from Douglas Weathers:
When shooting surises or sunsets you really can't make a bad shot. But to make it look even better white balance on blue and it will give it more of an "orange-yellow" look to it.
On certain cameras when you white balance it gives you the Color Temperature reading. If you have A and B sets so you can save them, try saving it at 9000K or higher and then shooting the sunrise or sunset with it.
SET IT AND FORGET IT!?
From: Jamie, NBC-41, Kansas City
Question: I've heard or read somewhere that "not" white balancing in some settings will give you much richer color. Recently I started "experimenting" with this...and it's particularly true in bar settings or concerts where colored gels might already be in place. BUT, when does this work well and when will I get burned by it?
Replying to Jamie at NBC-41, Kansas City (set it and forget it?)
Jamie, I've found that you've always got to white balance. What you want to remember when shooting under gelled lights is that the gels were placed there to achieve a look. If you white balance under an amber gel, for instance, you'll be color shifting your video away from what the lighting director had planned. The best way I've found is to white balance on something under a white halogen or tungsten light-a sheet of music, or even a shirt, provided it looks white to your eye. That way, the gelled lights will appear as designed.
BTW, when I work an accident scene at night, I always stop down and white balance on a steady burning (not flashing) headlight on a fire truck or police car. That way I know the red and blue lights of the emergency vehicles will appear as they should.
Jim Dean, Adelphia News 4, Forsyth County, GA
From: Jina Burn
Want your shots taken in shadow to be warmer and have no 812 or light? White balance through 1/8th blue or 1/4 blue in your Cinegel swatchbook. Learned this from an old dog from Virginia many years ago...btw: the swatch book will also help you out when shooting under the hideous brown sodium(?) lights so popular in many heavy duty repair shops.