Working With the Exposure Triangle to Adjust Scene Brightness


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I've been involved with photography for over 30 years. I began in the old days while working on my high school yearbook and have evolved with the changes in the industry every step of the way. Talk about how time goes by. I can remember hanging out in the darkroom with my friends, waiting and waiting and waiting.

Anyway, back in those days, because the cameras were so different and because we used film, we had to really learn photography and we had to make sure we applied what we learned as to take proper shots and not waste the film that cost us so much money. There was very little experimentation and what experimentation we did engage in was usually by accident. Supplies got expensive here and there, but we eventually picked up on how things worked and I became pretty good at my craft.

I want to share a bit of basic knowledge with you today because I think it may be helpful for folks who are new to photography. What I'd like to talk about will save you a lot of time down the road and hopefully it'll help you by removing some of the struggle we all feel when we're just starting out.

Basically, there are three primary parts to exposure in photography. Those parts are shutter speed, aperture and ISO. Shutter speed is the duration of time that passes when your camera's shutter moves to allow light to strike the sensor. The longer the shutter speed, the more light. Aperture is the hole inside of your lens that has the ability to grow and shrink. The larger the hole, the more light that's let through. And finally, ISO is the sensitivity of the sensor itself. ISO is like an amplifier. It can take whatever light that's being let through and amplify that light so it's viewed much more profoundly than it actually is. The higher the ISO value, the more sensitive the sensor.

When I talk about exposure, I'm referring to the brightness or darkness of a photograph. A properly exposed photo is one that looks just right. An overexposed photo is one that appears to be too bright and an underexposed photo is one that's too dark.

The big question is how to control exposure in photography. As I alluded to above, there are three primary methods we can employ. We can adjust the shutter speed, aperture and/or ISO. The issue is, each one of these methods comes at a price. You'll need to negotiate with your camera in order to produce a satisfying result.

Shutter speed controls not only how much light makes it through to the sensor, but it also controls how much blur appears in a resulting photo. If the shutter speed is very fast, you'll get a sharp, clean photo that contains very little, if any, movement at all. If you have a slow shutter speed and there are moving objects in your scene, you'll end up with blur in your image that appears like movement as well. It's these two areas that you'll need to decide on as you're out shooting. Brightness or darkness as well as motion blur.

When it comes to aperture, not only does the hole inside of the lens let more or less light through, it also controls what's referred to as depth of field. Depth of field is what makes some photos look soft in the foreground and background and sharp right at the center. The larger the aperture, the more light that's let through. With that, though, comes a shallower depth of field. Smaller aperture sizes offer a deeper depth of field. So if you're looking for a photo that's sharp from front to back, you'll need a very small aperture size, but just remember that the cost for that sharpness is light. Small apertures don't let much light through to the sensor at all.

Finally, we have ISO. If you keep your ISO value low, your sensor will be of average sensitivity. If you boost up the ISO value, you'll make the sensor much more sensitive to the light that's let through, giving you more leeway when it comes to darker, less lit scenes. The cost for that leeway is noise in your resulting image. The higher the ISO value, the more grain that's introduced. Again, this is the dance we must partake in as photographers. If we're dead set on keeping as much grain out of our photos as possible, we'll need to set that value to 100 (or lower, if possible). Then, we'll need to decide on where we're going to get our light from. A large aperture or a slow shutter speed.

If we don't want any blur at all in our shot, we'll need to keep the shutter speed very fast, but then we'll need to decide where we're going to get our light from. Either a large aperture size or a high ISO value.

And finally, if we want a deep depth of field in our shot, we'll need to decide if a higher ISO value is better than a slower shutter speed. While this seems cumbersome right now, as you get used to considering the attributes and limitations of each piece of the exposure triangle, you'll become so well versed that you won't even think about it anymore. I promise.

I hope this helped someone out there. Please let me know if it did and also let me know below if you have any questions.
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