ISO Sensitivity and Noise are an interesting topic. Depending on how you look at it, the explanations can be quite different. The standard photographer explanation is that a higher ISO sensitivity amplifies the light in an image while simultaneously amplifying noise. A more technical response, found on the photography Stack Exchange, suggests that, technically speaking, ISO sensitivity doesn’t create noise.

While there is some technical merit to those statements, the end result of choosing a higher ISO sensitivity is that there will be more noise in your photograph. This is not always a bad thing, though. The resulting amplification of light allows for a higher shutter speed or a smaller aperture – either of which may be necessary to execute a successful shot.

Here is a simple test to show you how these effects play out.  All of these shots were done on a Canon EOS Rebel t1i. The point here is to show how much noise is generated with this camera as the ISO sensitivity increases and the overall exposure is held constant.

To perform the test, I mounted the camera on a tripod and used the EOS Capture Utility to remotely trigger the shutter and alter the settings. I used my Canon EOS Rebel t1i with a Canon 85mm f/1.8 lens attached.

I started with ISO 100, and selected what seemed like a “proper exposure” – 1 second at f/5.6. Then, I held the aperture constant (so as not to effect the focus of the image), and as I increased the ISO by one stop I simultaneously decreased the shutter speed by a full stop. So at ISO 200, the shutter speed was 1/2 second. At ISO 400, the shutter speed was 1/4 second. So on and so forth.

To properly appreciate the results, click on the grid image to see it at full size. Each of those squares is a small sampling of the original image above – zoomed in to about 75% of actual size. Certainly there is some room here for perceptual differences, but I see no discernable difference between ISO 100 and 200, a slight amount of noise/speckling at 400, and the first significant amounts of noise at ISO 800. However, it is still quite understated at ISO 800. By ISO 1600, the noise is quite clear and at ISO 3200 it is more pronounced.

A few interesting points, however. First, take a look at the original image at the top of this post. That is the ISO 3200 image. Downsized to 625 pixels high, there is almost no perceptible noise. You have to view the image at a fairly high resolution (25-50% of original size) to appreciate the noise. If you’re viewing the images on the web, you’ll rarely look at an image that big. This will only make a difference if you’re using an uncropped image to make a very large print, or if you’re using a cropped image in a smaller print.

This also doesn’t taken into account the awesome noise reduction possibilities in Adobe Lightroom or Photoshop. Lightroom does an excellent job at noise reduction, although very high levels (50+) will lead to a significant softening of the overall image.

Also, the reason that I specified the camera being used (a Canon t1i) is that noise is a function of the image sensor and processor. Larger sensors with better processors (i.e. a Canon 5d MK II) will handle noise significantly better and allow for higher ISO shots with less noise.

Clearly, choosing a higher ISO rating than necessary leads to extra noise. However, if the image is still properly exposed, that noise may not be very apparent in most cases. The problem only becomes very pronounced when the resulting image is still underexposed, and the exposure is raised in post production. But this will be an example for another day.

In general, it’s better to choose an ISO setting that is at or slightly above your needs. In everyday shooting, I typically choose an ISO rating of 400 to 800, because I know this will give me more room to play with the shutter speed / aperture, and I know it won’t adversely effect the image. Moreover, I’ll happily switch to ISO 3200 if its necessary to get the proper shutter speed – i.e. basketball games, wrestling, or an indoor fashion show with no flash.

You’re camera has a setting called “exposure compensation,” usually labeled or represented by “EV” and a + or a -. What is exposure compensation, and why would you want to use it?

When you leave the camera in an automatic or semi-automatic mode (i.e. Automatic, Aperture Priority, Shutter Speed Priority), you let the camera pick some or all of the settings that determine an image’s exposure. The camera has a built in light-meter, and it makes an educated guess as to how bright or dark the image should be.

Sometimes… the camera doesn’t know what you want, and it makes the wrong guess. Exposure compensation helps you adjust that guess without going to a full manual mode. If you set it to +1, you’re telling the camera, “Take your best guess, and then make everything a little brighter.” If you set it to -1, you’re telling the camera, “Take your best guess, and then make everything a little darker.”

Keep reading…

Why use shutter priority mode when your outside with your speedlight…? Cause otherwise you’ll end up with a picture like this. Oops.

I had two new students taking pictures at graduation. That tends to happen every year, because my photography crew is all seniors… so they can’t really take pictures when they’re in the graduation. I’m also participating in the graduation, so I can give the new girls some hints here and there but I can’t follow them around and make sure everything goes smoothly.

In this case, I instructed them to try and shoot from the left side of the field, where the sun would come down and light everyone nicely (see post 1 of this series). Then I made the mistake of telling them that if they really needed to take a picture from the right side of the field, they could try putting the speedlight on top and seeing if that helped.

Keep reading…

In the first part of this series on shooting in sunlight, we looked at how to position yourself properly and utilize the sun as a light. In this second part, let’s think about what is the best camera setting or mode to use when working outside in bright sunlight? Keep reading…

A problem with cranking up the ISO setting on your camera is that your pictures will come out noisy. But does that mean you should never turn up the ISO setting on your camera…?

Nope. The picture to the left, from my coverage of the 2011 William Paterson University fashion show, was shot at the maximum regular ISO setting for my Canon EOS Rebel t1i – ISO 3200. When you zoom in to a 1:1 ratio, you can see some noise. However, I edited the picture in Lightroom and I also scaled it down in resolution for web viewing.

At this point, even if you click on the picture to bring up a full screen image, you won’t notice a whole bunch of noise. If you ask me, it looks great. I doubt it would look all that much different if I had put up a flash and stepped the ISO down to a more reasonable 400 or so.

Why Does the Picture Look Nice…?

Here’s another picture, from the same show and the same set up.

To give you an idea… I was sitting in the audience about 10 rows back. I had a telephoto zoom lens on the camera (70-200mm f/2.8).

The model started out in the back of the stage, where there was usable but slight amounts of light, and they walked down the runway into a bright, hot spotlight.

On the back of the stage, they were coming out ok at something like f/2.8, 1/125, ISO 3200. At the front of the stage under the spotlight, the models were perfectly well lit at f/2.8, 1/320, ISO 3200.

The key to the picture, and the reason that the noise isn’t terribly bad, is that there is enough light to brightly light the subject and allow for a proper exposure.

How Bout a Picture That’s Not So Nice…

In this picture, from the same show, there is considerably more noise. You might also notice that the picture looks a bit fuzzy as well as noisy.

The problem is that in this scene, the lights were not sufficient to light the models. The lights were dimmed for the whole scene (friendly warning, the gallery isn’t 100% safe for work), and I was shooting at f/2.8, 1/100, and ISO 3200. That was quick enough to prevent there from being too much motion blur or camera shake, but it left the pictures underexposed by about a stop.

This creates a two-fold problem. When the camera takes an underexposed picture, noise tends to be worse. Then, when you edit the picture (which I did in Lightroom, bumping the exposure by +1 and the Fill Light by 25), that noise gets exacerbated.

Add to that the fact that I cropped the picture, and you notice a lot of noise. To combat the noise, I jacked the Noise Reduction in Lightroom up to 50… and that kind of helps, but it also makes the picture a little fuzzy. It’s all a matter of compromise. The alternative would be not having a picture at all. Without a high ISO rating and without some help from Lightroom, I simply wouldn’t have been able to get any kind of usable picture from this scene with the lights dimmed.

In short, pictures taken at a high ISO can still look great if the subject is well lit. If you’re camera handles noise well and you run the image through software like Lightroom or Photoshop, a well exposed image will still look good. An underexposed image is going to look noisy, but you might just have to put up with it if you alternative is to not have a picture at all.

Aside from the exposure settings (aperture, shutter speed, ISO), there are a number of other important things to think about when using your camera. A lot of the time, you may not need to worry about them. But, when I go out to take photos at a sporting event, there are a series of settings that I routinely think about changing.

Here’s a quick rundown, so you can think about them next time too…

Autofocus Mode. On my Canon t1i, I can choose between One Shot Focus, AI Servo, or AI Focus (a hybrid of the two). Whenever I get ready to shoot sports, I immediately flip the autofocus mode to AI Servo. This tells the camera to continuously focus on the focus point until I take a picture, and the camera will continually refocus if the subject moves.

Why is this important? Well, in sports… people move. You also need to anticipate the action to get those good shots. So I spend a lot of time watching the game through the viewfinder with my finger halfway down on the shutter release button. This gets the camera to pre-focus on the moving subject, and when it’s action time I press the button down the rest of the way.

Autofocus Point Selection. On my Canon t1i, there are 9 focusing points. If you don’t change anything, the camera automatically selects which point it thinks it should focus on. Sometimes this works out, sometimes this doesn’t. If I’m shooting a group of people standing still, this isn’t a big deal. I can let go of the shutter release button, and let the camera choose a new focus point.

If, on the other hand, I’m in the middle of a football game… I don’t have time for second chances. When there are a lot of bodies around, I want to choose where the camera focuses. As a result, I generally manually choose a point, and it’s usually the center point. This way, the camera will focus on whatever I’m pointing the camera at.

In some sports (like wrestling), you don’t have to worry about the extra bodies and the camera will be able to do a much better job of picking out what it should focus on. As a result I’ve experimented with using the automatic point selection, because that frees me up from pointing the center of the lens directly at my subject.

This is potentially one of the biggest problems with not adjusting your settings for sports, though. If your camera is constantly guessing at the wrong focus point, try manual selection and see if that helps.

Continuous Shot. Continuous shot mode was made for sports. It’s hard to guess precisely when the best moment of action will be, and using continuous mode you can take two or three frames and hope that one of them comes out great.

Be careful how long you hold the shutter down, though. On the one hand, its a great way to fill up your memory cards too quickly. However, it can also fill up the internal memory (the buffer) on your camera and cause it to shut down for a few seconds until it finishes writing all the image data.

I found this out the hard way during a 55-meter shuttle hurdle race. In the race, a team of four sprinters take turns racing down a 55 meter stretch of track. The result is that in a matter of 20 to 25 seconds, four guys have zoomed by my camera and I’m trying to take pictures of all of them. I accidentally clipped off too many shots during the first leg of the relay, and the camera was struggling to empty the buffer and keep up for the rest of the (very brief) race.

Finally, Exposure. To me, the three settings above constitute “sports mode.” It gets my camera all set up to focus on action and take continuous shots. Once that’s done, I can worry about nailing down an acceptable exposure (or letting the camera do it in aperture-priority mode).

A very important setting, and one that my students often forget about, is the auto focus mode. In Canon, you’ve got three choices – One Shot, AI Focus (which we’re going to ignore for now) and AI Servo.

What’s the difference, and which should you use when?

Keep reading…

Not directly, no.

The DNG (Digital Negative) format is an open and standardized raw image format developed by Adobe. The Canon Rebel t1i does not have the capability to directly save an image in the DNG format. Keep reading…

“Shooting in raw” means that you’re saving your images to the memory card without processing them in camera. Instead, you’re saving that editing process for later, when you can sit at the computer and make sure everything comes out just right. While some people argue that you should just “get it right the first time,” that’s not always possible… and here’s one example.

Keep reading…

Something seem wrong with this picture? There surely is.

Your camera most likely has a “White Balance” button or setting on it. Chances are, you probably leave it on auto most of the time. If you don’t know what it does, that may be a good thing…

The image to the left is the result of using the wrong White Balance. My student photographers were shooting a football game yesterday, and one of them accidentally changed the White Balance setting to Tungsten. The result is a blue-ish tinge to the picture. Keep reading…