Auto Exposure Lock (AE-L) With Nikon D90

I thought this topic would be helpful to all of you who are interested in DSLR photography but fairly new into the field. I spent days to understand and implement Auto Exposure Lock feature and I feel like it is worth to share with you all so that you don’t have to spend much of your time. Although the idea is same for every DSLR camera, I am taking reference of Nikon D90 for the menu settings and have included couple of photographs I have taken with my D90. If you are using other DSLR, you may have to go through different menu options but you can always refer your camera manual for a quick search.

What is an Auto Exposure?

Camera automatically controls your camera exposure setting under different environmental situation depending upon the lighting condition. For example, if you are shooting any dark subject as a main subject with white background (enormous amount of light), your camera sets the exposure as per background and your main subject will come dark. That's why locking the exposure is very important to properly balance the lighting for your subject blended with different kinds of objects and backgrounds. There was a reader’s question about how to use AE-L/AF-L correctly and I posted a separate blog demonstrating the effect with the snow background. You can follow the link if you are interested to read more about it.

When should I use AE-L function?

The AE-L function can be useful when taking photos in tricky background situation so that the consistent exposure is achieved across the image, or when you wish to expose for the background and then recompose and shoot a photo so that you can achieve a better lighting effect on your subject over different environmental conditions.

How to set AE-L on Nikon D90?

1. Press the Menu button on the left hand side of your camera.

2. Navigate to the Custom Settings Menu (Pencil icon).

3. Go to f Controls menu and option f4 is for AE-L/AF-L button.

4. Select an option according to your need. You can also press the info (i) button to learn more about the particular menu item.

I recommend using AE lock (Hold) because it will lock the exposure and hold that setting until you push the AE-L/AF-L button again.

After the menu is set, you can lock the camera exposure by pressing the AE-L button once. You can find the Exposure Lock button to the right of your viewfinder, which is  labeled as AE-L/AF-L. Once you pressed this button, you can see the AE-L icon on the lower left corner of the viewfinder.

Let’s see how does it actually work in our real life example. I will try to explain it with the couple of shots I had taken for this purpose.

Without Auto Exposure Lock

I took this picture without locking the exposure. Camera controlled the exposure according to the white sky background and my main subject (building) came out bit darker than I would like it to be. Then I took my second picture using the exposure lock feature.

With Auto Exposure Lock

Now what I did in this case is I focused on the walkway (can be seen on the left bottom of the picture) which matches to the building color and locked the exposure (by pressing AE-L/AF-L button) to that settings so that any bright background won’t affect the exposure anymore.

When I took the picture with the exposure being locked at one value (referencing the sidewalk), it overexposed the sky little bit (not too much noticeable in this case) but the subject came out brighter. Sometimes this could create a problem if you are shooting with very bright sky and you have to be careful about the background lighting, how you want to expose your subject and your reference point to lock the exposure for the subject.

How To Shoot Fireworks With Nikon D90

When you are shooting fireworks, there are few camera settings you have to remember. Even though there are no definite rules, I'm trying to cover basic settings and things to remember before shooting the fireworks. Once you get the idea, you can play around and change your requirements like Aperture, Shutter Speed, ISO etc to adjust the exposure. To make it simple, I am taking the Nikon D90 as a reference for the menu settings. If you are using other DSLR, your navigation menu for the setting might be slightly different but the theory is same.

Things to remember before shooting fireworks

First of all, you have to get into the fireworks place at least 30 minutes prior shooting time to setup the camera on the tripod and choose the best location to view the fireworks. Being too close to the fireworks is also not a good choice for taking pictures. If you are too close, you might get lots of smoke coming out of the fireworks and ruin your picture. And most importantly, if you are planning to shoot fireworks without a tripod, you are probably wasting your time. Now let’s review the camera settings.

1. Turn your camera Mode dial into Manual Mode (M).

2. Set the ISO to the minimum possible value to avoid the noise in the picture.

3. Set the shutter speed 2 to 5 seconds and aperture f/11-f/14 to achieve the maximum depth of field throughout the frame. It will let the camera sensor to grab more lights and you will get the clear view of fireworks.

4. Set your lens focus into Manual Focus. Auto-focus is not good idea when you are trying to shoot long distance subject (moving fast) in a low light condition.

5. Use wired or wireless remote control to trigger the shutter release button to prevent the camera shake.

Tip: If you don't have a remote control, you can put the shutter release option into self timer mode and set the timer for 2 sec. That will trigger the shutter release button in 2 seconds after you pressed it which will avoid the potential camera shake.

Here is one of the fireworks shot I took on July 4th in Washington DC. Despite of being too close to the fireworks, it came out OK to me but learned a lesson for the future.

Focal Length - 18mm     Aperture - f/20     Exposure - 2 sec     ISO - 200

In this picture I set the exposure to 2 sec because I was too closed to the fireworks and they fired too many at the same time and as a result I got the overexposed shot with the 5 seconds of exposure time. You can always start with the recommended settings and then play around as you take more and more shots.