f stop/shutter speed underexpose
Ok...too many books and forum posts are starting to rattle my brain. No wonder I always used auto..

But time to grow up.

So if I am to underexpose an image by 1 or 2 stops (shooting in raw, to make sure I don't blow out my highlights) what does that mean? Does it mean I use a higher f stop and the corresponding shutter speed. Or am I to use a higher f stop but keep the shutter speed set for what it was at the original f stop? Can I even do that? I can feel the knowledge settling in but it isn't quite there yet..

And I guess this leads to the question do you ever use shutter speeds and f stops that don't match? Or is the only reason to adjust is to play with depth of field/ movement?.


Comments (6)

There are four aspects to exposure: Light, Aperture, Sensitivity, Time (LAST). Double any one of these (+1 stop), and you must halve another one (-1 stop) to remain at the same exposure..


* If you must control shadows, adjust the amount of light (flash, angle, etc.), and make up for changes elsewhere..

* If you must control focus, adjust Aperture (f/stop) and make up for it elsewhere..

* If you must control noise, adjust Sensitivity (ISO) and make up for it elsewhere..

* If you must control action, adjust Time (shutter speed) and make up for it elsewhere..

If you don't "make up for it elsewhere," then of course, you will have a brighter or darker image result..

[ e d @ h a l l e yc c ]

Comment #1

Good advice from Ed..

To be a bit more specific to the question of one stop in Manual mode only:.

If you want to underexpose by " 1 stop" then you take a meter reading and either close the lens one f-stop, or increase the shutter speed by one stop (double it). To over expose by 1 stop either open the lens one f-stop or slow the shutter by one stop (half the speed)..

If you are in any of the automatic modes you will not change the exposure by adjusting the aperture or the shutter speed because the camera will adjust the other parameter to maintain what it thinks is the correct exposure. If you are in automatic mode of some sort (Av, Tv, or the P mode) the easiest way to underexpose by one stop is to use Exposure Compensation of 1 stop under (see the manual). The camera will adjust things to give you underexposure of the value you dial in..

Now, that is how you adjust one stop either way. Deciding whether you need to is a very complicated choice, and depends greatly on what exactly you are actually metering..

Nothing is enough for the man to whom nothing is enough...

Comment #2

Thanks for the answers..

It all makes sense as I read it, but if I walk away form it I lose it. .

But eventually I am getting it..

Waiting for the new camera (Panasonic FZ50) and will then start practising..

I am assuming that exposure compensation and bracketing are the same thing. If I am worried about blowing out highlights then this might be the simplest fix and will give me the opportunity to see what happens when underexposed and overexposed..

I manipulate my images a lot so not sure why I am worrying, but in doing research on the cam to buy I have got hooked by all the knowledge in here. Figure if I know more I can do more..

Also the right combination of LAST is subjective I would think. For a photographer lookign to get the best image by these standards then it makes sense, but for someone like me who likes mistakes and working with them for special effects, then this could be played with. I say that as a statement, but perhaps it is a question..

And one last question. F2.8 - F3.7 / F11. This is the description for the camera I want. I understand F2.8 and F11, but am not sure what the F3.7/F11 means..

And thanks for the links too. I am getting quite the bookmark collection..


Comment #3

Mike143 wrote:.

I am assuming that exposure compensation and bracketing are the samething..

Not quite, but related. Bracketing is taking multiple (usually three) shots with DIFFERENT settings, so that you are more likely to have ONE that is good..

If you guess on the correct exposure, then shoot:.

* [sunny+f/16+ISO100+1/50sec] (twice the time)* [sunny+f/16+ISO100+1/100sec] (your initial guess)* [sunny+f/16+ISO100+1/200sec] (half the time).

That's bracketing. One of those three will be more pleasing than the other two. You shoot three for insurance..

[ e d @ h a l l e yc c ]

Comment #4

And one last question. F2.8 - F3.7 / F11. This is the description forthe camera I want. I understand F2.8 and F11, but am not sure whatthe F3.7/F11 means..

I will assume this is the description of the lense on your camera. This means that the maximum aperture (largest physical opening) is f/2.8 at the widest angle. It also means the maximum aperture is f/3.7 at the longest telephoto. It also means you can stop down to the smallest aperture of f/11 at any zoom setting..

Hope this helps. If you're still confused, just ask!.

Tim'Be the change you wish to see in the world.' -Mahatma Gandhi

Comment #5


That is one answer I don't have to think about.

Thanks got it!.


Comment #6

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This question was taken from a support group/message board and re-posted here so others can learn from it.


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