Choosing the number of frames: HDR

from Photo Insights June, 2022

Ask Jim

Photoshop will now combine all the images and, being in the ‘mean’ stack mode, will only retain the areas in the frame that didn’t move. That means all the people are magically gone.

It is possible to do this technique without a tripod. Photoshop does a great job at aligning all the frames. In the File > scripts > statistics dialog box, check the box at the bottom that reads, Attempt to Automatically Align Source Images. This approach isn’t guaranteed, but it’s worth a try if you don’t have a tripod.

If tripods are allowed where you’re shooting, you’ll be guaranteed the best possible quality with a firm support.

5. Get up early

Most tourists don’t get up early. They are on vacation. It’s only the serious shooters who set an alarm and wake up to photograph dawn or sunrise . . . or would-be crowded places devoid of people. The Bean in Chicago, for example, always has crowds around it except at 5:30 in the morning. Then there is virtually no one.

Inclement weather is also a good indicator that you’ll be able avoid crowds. The rare snowfall in Venice, Italy, above, shows San Marco Square without a single soul to ruin my picture. §

Choosing the number of frames for

HDR

One of the most difficult concepts in photography for beginners to grasp is that cameras and digital sensors don’t capture what we see. In some cases our images closely resemble what we see, but . . . we never see shallow depth of field, we never see elongated perspectives typical of wide angle lenses, and we never see the compression of elements characteristic of telephoto lenses.

Similarly, our eye-brain combination doesn’t have a problem with contrast. Highlights don’t ‘blow out’ when we look at birds with white feathers, for example, and shadows don’t go black even if there is a large discrepancy between bright and dark tones in any given situation.

Photography has always had a problem with contrast. First with film, now with digital, it’s tough for cameras to record detail when shooting contrasty scenes. The water cave in Portugal, below, is a good example. Even at 6:30am when the sun was low to the horizon, the sky

and the water were very bright while the rock structure facing me was in deep shadow. The only way to make this look like what we see -- or even better -- is by taking several exposures with one f/stop increments (this is the separation of exposures I prefer) and then combining them in Photoshop with third party software.

The question that always comes up is how many frames should you use to capture detail throughout the composition. Many cameras conveniently have automatic HDR commands in which the camera fires off 3 frames and then, on the LCD monitor, you see the HDR effect as a jpeg. For the high resolution composite, you have to do this in the computer.

This is a very easy thing to set up in the camera, and the results are quite good. However, with extreme contrast subject matter like the cave on the previous page or the shot of Casa Mila in Barcelona, Spain, below, three frames isn’t enough. For these two shots, I used 7 frames. The more contrast in the scene, the greater the number of frames is required.

The goal is to show discernible detail and texture in both the highlights and the shadows.

In the past I typically used 3 or 5 frames for each HDR sequence I shot, but I’ve switched to 7 frames because it’s like adding insurance to the mix. The most underexposed and overexposed frames can capture detail that might be missed with only 3 or 5 frames. In some scenarios, like the interior of the Cathedral in Siena, Italy, on the next page, I had to use a 9 frame HDR sequence. The stained glass window was exceedingly bright while underneath some of the arches the light level was many stops darker.