BeforeAfter_425

Single Exposure / Multiple Exposures

Need to make an exposure at a setting that’s sure to produce noise? Make a bunch of them. Then watch the noise disappear.

You can reduce noise in an image by combining multiple exposures of the same composition in Photoshop. Photoshop can search for the differences between the separate exposures and then blend them, keeping what stays the same and eliminating what changes. Random noise between separate exposures of the same composition will be substantially reduced, even dramatically, or disappear altogether. (This technique won’t eliminate fixed noise; hot pixels or column and row noise. There are other techniques for that, like using dark slides.)

You’ll find having this option will greatly reduce the reluctance you have towards using high ISOs. This means two things. You’ll be able to make images in lighting situations you thought you couldn’t and you’ll be able to make hand-held exposures in conditions you ordinarily wouldn’t be able to without severely compromising quality.

So how do you do this? Take these steps.
MultipleExposures_425

1      Shoot multiple exposures.

(Try to minimize camera motion as much as possible. It’s not necessary to use a tripod, but it can be helpful.)

ScriptLoadFilesIntoStack_425

2     In Photoshop go to File >  Scripts > Load Files into Stack

LoadLayers_425

3     Click Browse and select the exposures to be used in the Stack and check Attempt to Automatically Align Source Images and Create Smart Object after Loading Layers.

(The resulting Smart Object will contain all exposures in a single layer.)

StackMode_425

4     Go to Layer > Smart Objects > Image Stack Mode > Median to blend the separate exposures.

(You’ll see the noise substantially reduced.)

5     Optionally, compare the Image Stack Mode > Mean.

(This works best for exposures containing no movement.)

So what is Photoshop doing? Photoshop first aligns a series of images as separate layers, converts them into a Smart Object, and blends them, reducing or amplifying the differences between the layers with a variety of rendering modes. You can choose one of eleven rendering modes; Entropy, Kurtosis, Maximum, Mean, Median, Minimum, Range, Skewness, Standard Deviation, Summation, and Variance. Few people will ever use all of them; most won’t use any of them; but I recommend you try two – Median and Mean. (Stacks were designed for analytical tasks in various scientific fields, like astrophotography or forensics and they’ve since been put to many other uses.)

Median and Mean select values in between the highest and lowest values, smoothing out the differences between aligned layers in a stack. Median works best for images with some motion, either subject or camera, to remove moving objects or noise. Mean works best for processing exposures without motion. (Astrophotographers typically make many exposures, sometimes dozens or more, of the same subject and use Mean to reduce noise.)

The more exposures you make and combine the better the noise reduction. Only practical limits apply. How many exposures can you make? How many exposures can Photoshop process on your computer? You can stack and process as few as two images. Three is my recommended minimum. Six is better. After that, you get diminishing returns. (Try using your camera in burst mode more frequently.) The most challenging part of this technique is identifying situations where it’s helpful and remembering to make multiple exposures. If you have the exposures you can take advantage of this great feature; if you don’t have the exposures you can’t.

Combine the recent advances in digital cameras that offer exceptionally low noise at high ISOs, with new exposure techniques, with new post-processing techniques by the latest software, and you’ve got a profound paradigm shift in photography.

Learn these techniques and you’ll find your photographic options will expand dramatically. The most challenging thing isn’t learning the techniques; the most challenging thing is redefining what’s possible and practical. You’ve got to experience it to truly understand it.

Read more on Noise here.

Learn more in my digital photography and digital printing workshops.

Hand_BeforeAfter

Learn how to make the most of your images!

Come join us for a 3 day no-holds-barred seminar on digital image processing led by two long-time industry leaders!

Demonstrations will include essential new features you need to know about in Lightroom 5 and Photoshop CC. Master the most advanced cataloging, keywording, searching, and filtering capabilities of Lightroom. Learn best practices for using Lightroom at home, on the road, and even on a network. See how you can efficiently share your images in slideshows, web galleries, social networks and print. You’ll know what to do in Lightroom and what to do in Photoshop, when to do it, and how to move back and forth seamlessly between the two.

We’ll cover all the ins and outs of developing Raw files. You’ll see what every slider in Lightroom’s Develop Module / Adobe Camera Raw does. And then we’ll show you how to double process and even use Camera Raw as a filter allowing you to use all of Photoshop’s advanced masking capabilities. You’ll see two top pros process their own files and each other’s files.

You’ll be dazzled by game-changing multi-shot processing techniques – including HDR, panorama, focus-stacking and more. You’ll be wowed by our creative uses of Photoshop’s most advanced sharpening and blurring tools. Witness the most advanced color adjustment strategies you’ll find anywhere. Combine them with the most sophisticated selections and masks to master the interpretive art of dodging and burning.

You’ll be able to take your files to a whole new level!

Register now!

Sossusvlei_BeforeAfter

“Learn to combine multiple exposures together into one composite shot with Adobe Photoshop CS6. Russell Brown demonstrates stacking images and using advanced blend modes to combine multiple images together.”

View more Photoshop videos here.
Learn more in my digital photography and digital printing workshops.


Subscribe

Get the RSS Feed  

Subscribe by Email