Photo Tips San Diego Underwater Photographic Society
Photo Tips
San Diego Underwater Photographic Society
| PUSH IT by Randy Morse Have you ever been in a position where the available light was just a little too low or your subject was moving just a little too fast for your film speed? Where you knew that if you just had one more f-stop or one faster shutter speed, you would of had it made. Obviously, one answer for these problems would be to switch films, to one having a faster speed/ASA rating. Although how many of us are willing to buy double or triple the amount of film for a big trip, just to cover all the possible film speeds we might need? Another solution is to shoot your standard film at a faster ASA setting. Then have the lab alter the development process to increase the effective ASA to match what you selected on your camera. This is known as Push Processing, which can be a very effective tool given a few limitations. Lets look at an example where pushing could make the difference. You are using a 100 ASA slide film and photographing sea lions on a broken overcast day. The shutter speed is at at 125th of a second. The sea lions are darting in and out of your frame and you just know that 125th is not going to be enough to stop all the motion. If you set the camera at 250th of a second, then you are forced to open up your aperture another stop and depth of field then becomes a problem. The solution is to shoot the 100 ASA film as if it were 200 ASA film. You can do this manually by setting the camera ASA setting to 200. By doing this you have gained one f-stop. In the above example you could now set your shutter speed to 250th and leave the aperture setting unchanged. Or if you were in a low light situation shooting at say f4. By pushing one stop, you would be able to shoot at f5.6. This may not seem like much, but one stop will often make or break an image. |
So this is great, your 100ASA film is now a 200 ASA film
if pushed one stop, or it could become a 400 ASA film if pushed two stops
or it could it be...well not quite. Lets talk about the limitations which
I already mentioned. As you push process film, the more it is pushed, the
more contrast is added to the final result. More contrast means that dark
areas get darker and light areas get lighter. Because of this you begin
to lose detail. The apparent grain of the film will also increase. The
color balance will also change. My experience has been that most E6 slide
films can be pushed no more than one f-stop. This means a 50 ASA film can
be shot at 100 ASA, or a 100 ASA film can be shot at 200 ASA, with little
loss of detail or color balance. Every brand of slide film will react differently
to pushing, so doing a few test rolls is a must.
A few things to remember if you are going to push. When you push film, you must shoot the entire roll with the camera set at the same higher ASA setting, because the entire roll will be push processed in the lab. You will need to tell the lab how much to push process the roll. In the above example, a 100 ASA film was shot at 200 ASA which is a one f-stop increase or what is known as a one stop push or Push One by the lab. I always keep a permanent marker in my film bag and write +1 or whatever the push amount was on each film canister. Also keep in mind that you will likely be charged an extra couple of bucks per roll for this service. Another service a professional lab can offer is called a snip test. If you felt you had under or overexposed a roll of film and had some shots you really wanted to save, you could have the lab do a snip test. To do this the lab will cut off, snip, the first few frames on the roll and process them. You could then review these frames and decide on how much to push or pull the processing on the rest of the roll. This of course means that you will likely lose the first few frames from the roll and you will be charged a premium for this service. Your questions and comments are welcomed. Randy Morse |
