What does it mean "expose and step up 2 stops"

Tatiana_ · Nov 24, 2014

I'm reading an article on "how to expose for people". And it basically says expose on the brightest part of the face and alter your shutter speed so as the meter is now 2 stops above middle grey.
What does "expose" exactly involve in manual mode?? Set what to what? How do I know I have "exposed"?
And then the second part about shutter speed. Is it slowing down or making it faster? Just the shutter speed, nothing else?

Or another article - it says " your camera will underexpose cuz there is a lot of light (portrait in sunshine) but you need to override and slow down your shutter speed enough to create bright skin tones. Again, how exactly do I do that?

KmH · Nov 24, 2014

Camera Exposure: Aperture, ISO & Shutter Speed

A Stop
A stop is a fundamental photography concept.

A 'stop' is a doubling (2x) or a halving (0.5x) of the amount of light that reaches the recording media be it film or an electronic sensor.
A stop change in exposure can apply to shutter speed, lens aperture, and/or ISO.

Since exposure is a triad of adjustments (shutter speed, ISO, lens aperture) you can change 1, 2 or all 3 of the triad settings.

If you want 1 more stop of exposure (brighter) you can adjust just one of the 3 by 1 more stop.
Or, you can change 2 of the 3 by 1/2 more stop each for a net gain of 1 stop of exposure.
Or, you can adjust all 3 by 1/3 more stop for a net gain of 1 stop of exposure.

You can also change the triad of settings and have no change in the exposure.
If you change 1 of the 3 settings by 1 stop more exposure and change a 2nd setting by 1 stop less exposure the net change is zero.

Suppose you subtracted a stop of shutter speed to help stop subject motion, you could add a stop of lens aperture to keep the exposure the same. However, adding a stop of aperture will also affect the total DoF by a small amount. So, if you don't want the DoF to change you would add a stop of ISO instead, however, adding a stop of ISO will increase by some amount the image noise in the photo.

Note: DSLR cameras are set by default to adjust the exposure settings in 1/3 stop increments.
Most DSLR cameras let you change that to 1/2 stop or 1 stop increments.
However, the advantage of 1/3 stop step increments is more precise control of exposure.

Tatiana_ · Nov 24, 2014

Ok, just to clarify. I set my camera in M. And I set Iso, shutter and aperture to smth. How do I know I've achieved exposure? Is it based on my personal opinion or is there a rule to say "it is indeed correct exposure"

Sorry to be redundant. Trying to understand

JustJazzie · Nov 24, 2014

Have you read your cameras manual? You will want to know how to use the light meter in your camera. I believe you would want to place it on "spot" metering, then meter off the face for correct exposure and then once you have established what is "correct" decide which setting you want to change to achieve your overexposure.

JustJazzie · Nov 24, 2014

Tatiana_ said:
Ok, just to clarify. I set my camera in M. And I set Iso, shutter and aperture to smth. How do I know I've achieved exposure? Is it based on my personal opinion or is there a rule to say "it is indeed correct exposure"

Sorry to be redundant. Trying to understand

You will use your cameras built in light meter.

Rick50 · Nov 24, 2014

Do yourself a huge favor and read this book by Bryan Peterson.
http://www.amazon.com/Understanding...887344&sr=1-1&keywords=understanding+exposure

Derrel · Nov 24, 2014

Well, with the camera in Manual exposure mode, take a close-up reading of the face using center-weighted metering, from not too far away; this is called a close-up reading, and it works better than a spotr meter reading because it averages out the tones and make the reading more consistently "baseline= the face".

Center the light meter scale at 0.0. Then, with the standard way of using 1/3 stop exposure adjustments, click the aperture "up" six clicks, which is TWO full stops.

Or, click the shutter speed dial six clicks slooooooooower.

Or, split the difference, and open the lens aperture up three clicks, like from say f/11, to f/8, and slow the shutter three clicks, say from 1/500 second down to 1/250 second.

This is a way to over-expose two stops from the light meter's suggested exposure level.

bratkinson · Nov 25, 2014

Perhaps the biggest 'leap' in my learning the exposure triangle was when I started doing nighttime photography about 35 years ago. I had to rely on my handheld meter to determine 'where to start' and then applied what I had learned about exposure bracketing to get one or two 'keepers' from 6-8 shots.

Perhaps the most significant exposure triangle issue is shutter speed. Having a </sarcasm on>'super speedy' ASA (ISO) 100 film at the time </sarcasm off>, and having my lens wide open at f3.5, I was only able to adjust the shutter speed for longer and longer exposures, hoping to get a keeper. Keep in mind that back in the film days, there was no 'instant feedback' on how over/under exposed the image was. You trusted your meter and your experience.

One series of shots I remember taking was a nighttime shot of the US Capitol Building in Washington DC. Not having a tripod handy (I was on a business trip, after all) I had to find a substitute. A square-topped trash can and cable release worked perfectly. Shooting across a calm reflecting pond/pool, I changed my shutter speed from about 2 seconds to perhaps 10 seconds, 1 second longer each shot. Why did I start at 2 seconds? After setting my meter for the film speed (ISO) and aperture, it showed 3-4 seconds for the exposure.

In looking through the results (I shot slides back then), the first couple of shots were all too dark. With each longer exposure, the Capitol Building got more and more visible. It was about bright enough, but then, to my surprise, a statue of some famous person on a horse in a shadow area (some army general, I presume), started becoming visible as well.

That exercise showed me the effect of changing shutter speed while keeping the other 2 components of the exposure triangle constant. Today, I could use a 'faster' (larger aperture) lens to increase the total light reaching the sensor. I could crank up the ISO speed as well to make it respond 'faster' to the light hitting the sensor. I could still change the shutter speed as well. As mentioned previously, I could double the exposure time (2 seconds to 4 seconds, for example), and double the ISO speed (perhaps 1600 to 3200), adjusting each by 1 stop. How many stops and how to achieve it is what makes the exposure triangle so interesting.

Torus34 · Nov 25, 2014

Tatiana:

The 'correct' exposure for a picture is a bit of a fuzzy concept. What one photographer will want a final print to look like may not be what another would desire. So ...

Your camera can let you explore this by 'bracketing'. All that means is that you take the same shot at different exposures -- some 'lighter' and some 'darker' than the camera says is 'best'. You then pick the one you want and scrap the rest. After you've done this a few times you'll come to know, in advance, what change in exposure you'll want for certain types of shots.

Find someone who wouldn't mind acting as a subject for you. If your camera has a 'center weighted' metering setting, select it. Pick a nice day outdoors and set the ISO at 100. Set your camera on 'Auto' exposure, move in close to the subject's face and see what the camera says it has selected as a shutter speed and lens opening [stop].

Now shift the camera's setting to 'Manual'. Set the same lens opening and shutter speed that the camera had selected on 'Auto'. Take a picture of the subject. Then change the shutter speed to one stop faster [say, from 1/50th to 1/100th sec.] and take another picture. Don't change the lens opening. Again shift the shutter speed one stop faster and take a third picture, again without changing the lens opening. Finally, go the other way -- from 1/50th to 1/25th sec.

You now have four pictures: 'normal', one stop under-exposed, two stops under-exposed and one stop over-exposed. You can transfer them to your 'puter and see the differences.

That's 'bracketing'. For subjects that don't move, you can use a tripod and bracket, getting absolutely identical shots except for the exposure. I do this routinely when I shoot film of contrasty subjects.

Braineack · Nov 25, 2014

Tatiana_ said:
What does "expose" exactly involve in manual mode??

You put the camera in M mode so the camera doesn't change the shutter and aperture based on your meter reading.

Set what to what? How do I know I have "exposed"?

Need basic understanding on how your light meter on your camera works.

And then the second part about shutter speed. Is it slowing down or making it faster? Just the shutter speed, nothing else?

slowing the shutter will allow more light, thus making the image brighter.

Here's the point behind the method:

Your camera's meter tries to make everything gray. In auto mode, if you point it at the brightest part of the face, and take a picture, it will actually be dark. This is because the camera saw a bunch of white area and changed the settings to make it so it exposed as gray.

Adding two stops of light above middle gray is pretty much white. But not too much that there's no information behind it. What you don't want to do is "Clip" the whites. I'd suggest a google search here on clipping, but once the whites are clipped, there's no information behind it to recover the image if you want to make it darker in that area.

So this author is suggesting that you find the brightest part of the face, set the camera so it's gray, then set the camera two stops above that so it's now going to be close to white without clipping (either shutter speed-slower, aperture-wider, or ISO-higher).

480sparky · Nov 25, 2014

What does it mean "expose and step up 2 stops"

It means the writer didn't proofread his/her own work.

Replace the word 'expose' with 'meter' and see if it makes sense.

"Meter and step up 2 stops"

Tatiana_ · Nov 25, 2014

Torus34 said:
Tatiana:

The 'correct' exposure for a picture is a bit of a fuzzy concept. What one photographer will want a final print to look like may not be what another would desire. So ...

Your camera can let you explore this by 'bracketing'. All that means is that you take the same shot at different exposures -- some 'lighter' and some 'darker' than the camera says is 'best'. You then pick the one you want and scrap the rest. After you've done this a few times you'll come to know, in advance, what change in exposure you'll want for certain types of shots.

Find someone who wouldn't mind acting as a subject for you. If your camera has a 'center weighted' metering setting, select it. Pick a nice day outdoors and set the ISO at 100. Set your camera on 'Auto' exposure, move in close to the subject's face and see what the camera says it has selected as a shutter speed and lens opening [stop].

Now shift the camera's setting to 'Manual'. Set the same lens opening and shutter speed that the camera had selected on 'Auto'. Take a picture of the subject. Then change the shutter speed to one stop faster [say, from 1/50th to 1/100th sec.] and take another picture. Don't change the lens opening. Again shift the shutter speed one stop faster and take a third picture, again without changing the lens opening. Finally, go the other way -- from 1/50th to 1/25th sec.

You now have four pictures: 'normal', one stop under-exposed, two stops under-exposed and one stop over-exposed. You can transfer them to your 'puter and see the differences.

That's 'bracketing'. For subjects that don't move, you can use a tripod and bracket, getting absolutely identical shots except for the exposure. I do this routinely when I shoot film of contrasty subjects.

Ok, I think I'm finally getting what is so obvious to all of you but not to me. I think I was not clear how to meter in Manual mode because I was thinking the settings are what I make them to be. So then how is the camera telling me what it's metering if the settings are what I set them. What you are saying is that I use the auto mode to see what it meters and then step up or down from those measurements in manual mode. Is that right? Sorry, don't have the manual with me and quick Google search hasn't helped yet.

ronlane · Nov 25, 2014

You may want the settings in Manual mode to be ISO 200, F/4 at 1/1000 of a second to be able to stop action and have the back ground out of focus. But the camera when the camera looks at the scene and meters for the "correct" exposure, it may be 2 stops too bright.

You then have a creative choice to make. Do you leave it at your settings are do you stop down 2 stops. This can be done as suggested above.

Basically the camera is going to look at the scene and compare what it thinks is correct exposure for that scene against what settings you have put in the camera.