What is the use,the different and the result of using compensation in the flash and in the camera?

Question

What is the effect if we add some compensation in the camera and in the flash? Is it to get the pictures brighter for the background as well as the object? How about if we increase the ISO then? Thank you for your help

Answer 1

Compensation is a manual adjustment to increase or decrease exposure. For instance, if your whites turn grey (like snow), you need to "step-up" compensation (+ ) to slow down shutter speed. On the other hand, if someone's black shirt turns dark grey when you take a photo, you need to "step down" compensation (-). STepping down increases shutter speed to allow less light into the camera thereby darkening the overall "tone" of the photo. Compensation is a manual adjustment to your automatic mode to correct exposure. Sometimes, the camera's metering system is tricked by the photo to take wrong colors. Predominantly white snow is sometimes taken grey because the metering system sees the white color as overexposure. The camera compensates overexposure by increasing shutter speed thereby darkening the photo.

The direct flash does the same effect - the camera meters based on the closest subject then renders the background dark because of the strong flash. If you want to get more background, check:
1) if your camera has a slow flash sync or a Night Mode. This essentially syncs the flash with a slow shutter speed to get more background.
2) Or you can also buy an external flash that has bounce capabilities (you can angle the flash upward).
3) Or, you can take the foto without the flash and ask your subjects to stay very still because of the slow shutter speed. Better use a tripod and use the self timer to avoid camera shake. Under this flashless mode, you may crank up the ISO to increase shutter speed and reduce the possibility of blurring caused by camera shake. But increasing the ISO will make your photo grainy. 800 ISO is ok.

Answer 2

Compensation? Most flashes are automatic, that is, they measure the light as it is reflected back and stop the flash when it is sufficient. It usually determines the aperature and ISO information from the camera, otherwise it is a dial in setting.

If the flash is manual (such as a bulb or external strobe) then it has a "guide number" The guide provides you with a suggested exposure aperature when divided by distance to subject. The guide number applies to 100 iso film, it would be double for 400 speed. Very strong strobes sometimes give you an option of reducing the flash power. This will increase aperature setting to reduce depth of field for portraits.

The other compensation might be when using a flash for fill in when there is daylight or other light source. Again the automatic flash reads total lighting, so it should be accurate. Manual adjustment require you condsider both sources of light. Your light meter will give a recommended exposure for the ambient light. Compare this to the guide number calculation for the strobe. If they agree then the dark shadow areas of your subject will be brightened by the flash for a normal exposure.

Another factor when using 35mm SLR with focal plane shutters is that there is a maximum speed setting for having the entire film plane open is quite low, usually between 1/30 to 1/100 second depending on camera model. This is slow enough that the mixed lighting conditions may be too bright to get a match with the guide number, the only help would be a stronger flash.

Answer 3

Well most other folks have covered the obvious things to so, especially Caio. Moving back a bit & zooming is good advice, but remember that most P&S flashes aren't that powerful (about 3m range) so don't go back too far! Using tissue or paper over the flash is a good tip. Additionally if you want to 'warm' the flash up a bit you could try a bit of pale yellow or orange cellophane over it (a sweet wrapper would do). Photographers often use either 1/4 or 1/2 CTO gel (a pale orange film) to do the same. Slow synchro flash will allow more of the ambient (background) light to contribute to the image - this can often help because it reduces the contrast in the image (your friends faces will look less like they've been 'nuked' against a black background). The button press to focus you ain't gonna change - processing the image & writing to memory times for P&S cameras are similarly notoriously slow. The only way round this is to go for a DLSR or look for a camera that has a very short 'shutter lag'.

Answer 4

Flash info and tutorials:
http://www.chem.helsinki.fi/~toomas/photo/flash-faq.html
http://www.sederquist.com/claflash.html