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Just a copy and paste from a small article which I posted on AMC some time back. Slightly tweaked and updated.
Mastering manual exposure setting - the easy way
by soulfly
I love manual setting. It gives me full control of the camera and pretty much the only shooting mode that could produce shots the way that I wanted.
Manual exposure setting is actually not very hard to understand if you know the basics in getting consistent exposures. Nowadays, we are blessed with TTL metering from out DSLRs. It is good enough. You won't really need an external flash/light meter (unless you're doing portrait lighting which meters make your jobs much easier). Take advantage of the TTL metering and just keep your eye on the EV meter in the viewfinder. Combined with suitable metering mode, just keep the EV value at 0 and you'll be safe. And if you get underexposed image, the LCD screen will show it and you can re-shoot. Another bless with digital that you don't need to develop the shots to view it like you do on film. Saves cost.
To nail the basics into your head, I will divide this little article of mine into a few parts:-
1. aperture
2. shutter speed
3. iso
...assume that we are not using the flash, yet.
Aperture
This property directly reacts to three things - overall exposure, depth of field (DOF), artificial light (we will leave this one for the next part).
- larger aperture (small f-number) = bright exposure and thin DOF
- smaller aperture (big f-number) = darker exposure and deeper/wider DOF
Let say we have a few different shooting cases:
1) portrait/candids/street - Always use the largest aperture possible. For people, f2.8 seems to be the most comfortable value to get every part of body in focus. But there's no harm to use larger aperture like f1.8 or f2.0, as long as you have just enough DOF. If you have a lens with no constant aperture, use the largest aperture of the focal length that you are using.
2) group photo/multiple subjects - For this, to be safe I'd use something around f5.6~f8.0. f4.0 is fine, but not lower - that if you want to make sure everybody/everything in focus. Use smaller aperture, like f11 or more, if subjects are not placed within a line or scattered around the frame. Your point of focus would be the most important person in the frame, or focus to the person 'behind' the person at the most front.
3) landscape - Use as small as possible to capture more DOF. I always like to use f8.0 with my kit lens (Sony SAL1870). Some people likes to use f9.0~f11.0. No harm trying.
* Stopping down the aperture might also increase the image sharpness. Different lens react with different stop down value. We call it, the 'sweet spot'. The main reason to this is that more focus to the subject, which tends to make it look sharper. Remember, focus = sharp.
Shutter speed
This property directly reacts with two things - ambient light and speed of movement. To make it simple (let say we have a fixed aperture and ISO setting):-
- faster shutter speed = darker ambient
- slower shutter speed = brighter ambient
Let say we have a few different shooting cases:
1) static objects - You can use any shutter speed you want, as long as you can keep your camera stable (image stabilizers, tripod, bean bags, strong muscular and steady arms, black magic, etc.).
2) moving objects - To be safe, use at least 1/80 sec. for slow moving subjects like people sitting down and just chilling out, or 1/125 sec. for walking people. If you want a motion effect, use panning method. Turn off the SSS if possible, it will give better result.
When you think that your shutter speed is already at your limit (too slow to keep you steady), bump the ISO up accordingly.
SSS does not freeze motion, it only helps giving stability in holding the camera.
ISO
This is always the first and last thing you would adjust from your camera. ISO reacts directly to overall exposure. On digital (image sensor), every stop increase amplifies more current to the image sensor to make it more sensitive to light. The negative to this is more heat. The hotter the sensor gets, the more it tends to produce noise. This what appears in photos as grain or colour blotches. Grain noise is okay, but you would want to avoid colour blotches if possible.
...but it is always better to capture grainy images than blurry images.
My method:
1. To begin shooting, I always prefer to set a 'base ISO' depends on my condition:-
- bright outdoor: ISO100
- indoors: ISO400
- night outdoor: ISO800
2. Then, I would adjust my aperture depends on my subject (refer to Aperture).
3. Then I set the shutterspeed accordingly. Follow the EV meter inside the viewfinder. But be careful not to get too slow. If I am shooting people, I will make sure than 1/80 sec. is the minimum, or maybe 1/60 sec. if I get adventurous. Or else, I'd just bump up my ISO until I get the proper exposure (EV more or less at 0). Do not touch the aperture if possible.
* If you're shooting night landscape, it is best to use a tripod, low ISO and long shutter speed. This way you could capture the beauty of night scenery. However if you're street shooting, you might wanna use high ISO and faster shutter speed instead. It depends on your subject really.
...and again I would say, keep your eye on the EV meter, you'll be safe.
If you still can't get a good exposure, it's time for flash.
By the way, my favourite metering and focus mode is multi-segment metering plus local AF point select. Personally I think this combination is the most versatile and gives me the most consistent exposure most of the time.
Now... open to comments and questions.
DOF = depth of field (areas in focus)
EV = exposure value (with EV at 0 being 'constant', EV to the left (-) being underexpose, EV to the right (+) being overexpose
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