Stacking and Blending and HDR-Oh My!

I’ve been getting a lot of questions lately about the various techniques I use for combining multiple images. What’s the difference between “stacking” and “blending,” and why would you choose one of these methods over HDR?

First, I need to make it clear that I have no clue about the proper terminology for any of this, or even if such a thing exists. As I’ve done with most things in life, I pretty much make it up as I go along. What I do in Photoshop and other programs works for me and the terms I use to describe it seem to be appropriate.

Okay, it doesn’t ALWAYS work for me, but it does most of the time. Okay, some of the time.

I don’t want to get into a discussion about the ethics of combining multiple exposures. It’s early in the morning and I’m not in the right mood for summoning up my ranting voice, so we’ll save that for an evening post after I’ve had a few glasses of wine. Suffice it to say for now that for the vast majority of images, the reason I use multiple exposures is because it is the only way to record the scene as I see it or as how I wish to portray it. And since they are my photos, I’ll create them the way I want to. Single exposures work for most images captured in the day and a lot of them captured at night, but that still leaves a vast amount of situations that need these additional processing techniques.

However, I will never hide behind my methods and make you think a photo is from a single exposure when I’ve used some other technique.

Stacked

When I say, “stacked,” I’m talking about stacking two or more pics as layers in Photoshop. From Bridge, choose Tools>Photoshop>Load Files into Photoshop Layers. From the Library or Develop module in Lightroom, choose Photo>Edit In>Open as Layers in Photoshop. Both of these methods will automatically open Photoshop and stack the files as layers.

Car Light Streaks-Venus-Twilight

This image is a stack of 4 separate frames with the blend mode changed to Lighten so all the light streaks show up on one photo.

Car light streaks layers

The 4 photos used to create the stack of car light streaks. These individual photos are straight from the RAW files, with almost no post processing performed.

If you already have two or more files open in Photoshop, you can manually stack them. Choose the Move tool and drag one photo on top of another. If you hold down the Shift key as you drag the image and keep it held as you release it, it will register perfectly with the photo underneath. This is critical so that all the elements from each image register precisely. Of course, this means you have to shoot all the layers with the camera mounted on a tripod. You can certainly stack photos that you didn’t shoot at the same time, but there’s no need to hold the Shift key when you stack them because you’ll probably want to position them manually.

With all of these methods, once the photos are stacked, you’ll see them in the Layers palette. Very often, the next step I take is to change the Blend mode of each layer to Lighten so that all the light parts show up. That’s what you’ll want to use for things like star trails, light painting, and combining multiple shots of car light streaks.

Occasionally, I’ll use other blending modes, and might even use different modes for different layers in the same photo, but in all cases with a Stacked image, I’m using blend modes to achieve the desired result.

Blended

When I say “Blend,” I’m taking two photos and loading them as layers, just as with Stacked, but I don’t change the blend mode. Instead, I use a layer mask and brush out parts of the photos so that only the best parts from each one show up. A good example is shooting two pics for a waterfall. One is for the water and one is for the surroundings. I stack the two, and then brush out the overexposed water from the shot I made for the surroundings, which reveals the properly exposed water beneath. The same technique works well for sunrises and sunsets, when you shoot one pic for the sky and one for the foreground.

Occasionally, I’ll stack three or more photos and use this technique but in most cases, two is all I need.

Waterfall created from 2 exposures blended

This photo is blend of 2 photos, one for the water and one for the surroundings.

Waterfall image layers

The 2 photos used to create the blend of the waterfall image. These individual photos are straight from the RAW files, with almost no additional post processing performed.

HDR

With HDR, I take three or more photos and let the software (Photoshop, Photomatix, or Nik) do all the blending work for me. When the software finishes with the photo, I usually have to fine-tune it in Photoshop, but the software has done the hard work for me.

LeConte Lodge dining room

This photo of the dining room in LeConte Lodge atop Mount LeConte in Great Smoky Mountains National Park is an HDR created from 6 bracketed exposures.

LeConte Lodge layers

The 6 frames used to create the LeConte Lodge dining room photo. These individual photos are straight from the RAW files, with almost no additional post processing performed.

Which one?

So the big question is which one you should use. That depends on the type of image you’re shooting. If you’re doing night photography and want to combine the light parts from multiple frames, you’ll want to go with Stacked. If the scene consists of light and dark areas that are too extreme for one image to capture, there is a relatively distinct transition between these contrasts, and there aren’t a lot of little extremes scattered all across the scene, a Blend is the way to go. If the scene has too much contrast to record properly in a single capture and the transitions are not well defined, or if the contrasty areas are small and scattered all about, HDR is the ticket.

We’ll be talking about some of the opinions people have about using these techniques later on. For now, I’ll leave you with this tidbit. Regardless of where you stand on the issue, I’d be willing to bet that if you go online and find 100 photos that you love, a good number of them will have been processed using some version of one of these three techniques.

Money in the bank.

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