A Virtual Tripod with Photoshop CS4 Extended

This techique describes a method to stack several high ISO source images in Photoshop CS3 or CS4 Extended, in order to minimize random noise – in effect creating a synthesized long duration low-ISO exposure.

It is the first in a series of techniques relating to ‘computational photography’ – the process of utilizing several source images and raw computer power to enhance your final image output.

So you are at an art museum. You’ve got your shiny new DSLR with you, but the strict rules of the museum excludes both tripod and flash use. Unfortunately the art pieces are not all that well lit, maybe just the equivalent of a single incandescent lightbulb from the distance of a couple of meters.

– But you really want to get that depiction of a museum piece… What do you do?

My Canon 40D features a maximum of 6.5 frames per second. Instead of taking one exposure at high ISO, I can take a sequence of exposures at high ISO, and then combine all of them in a Photoshop Stack to create an image devoid of the rampant random noise. Photoshop aligns, then averages the pixels from each shot to create noise free pixels, and extract details otherwise obscured. The reason this works is because the noise is random – it is rarely in the same spot in two seperate images.

Astronomers has stacked images like this for a long time, indeed they have some very sophisticated software available to them, but now everyone with a copy of Photoshop Extended can utilize its powerful align and stack algorithms to do this trick.

Here’s the workflow:

1) Set an exposure suitable for the lighting and for handholding. For a painting, you don’t need much DOF, so an open aperture is suitable, just choose the first aperture that is sharp for your lens. In this example, my camera settings were: RAW, 1/160s f 2.2 ISO 3200. I want a fast shutterspeed for my 50mm 1.4 to ensure sharpness across the handheld sequence I’m about to make. I choose the highest ISO setting on my camera, ignoring any noise issues for now.

2) Angle the shot, focus, brace the camera as best you can, and hold down the shutter for as long as necessary. The more shots you have, the better a result you can expect, but you should also expect a longer processing time. My Canon 40D filled its buffer at 15 photos at 10MP RAW format, and it took it just a bit over 2 seconds to do so.

3) So, now you’ve got 15 noisy, virtually useless, slightly underexposed ISO 3200 shots of the same washed out painting. Great.

At this point, back at my computer, I open up Bridge, and examine details with the Loupe on all of the frames. If one or two are out of focus, I delete them or exclude them. Then I open up all of the remaining sharp shots in Camera Raw. I make sure to select them all, dial in a +1 exposure, because I had to underexpose the shots a bit to get a faster shutter speed. This will push my source images to ISO 6400(!). I carefully adjust the WB and other settings. I like to keep a linear tone curve for this technique, but your mileage may vary. You may even add a bit of capture sharpening, disregarding the hit you take in noise. – But do turn off all noise reduction, as we will deal with this in the next step.

I usually keep to a 16-bit Prophoto workflow, but I find that for a 15 image stack in Photoshop, it might just be to much data crunching to wait for, so I made my source images 8-bit Adobe RGB in this case. See screenshot:

Camera RAW - 15 photos selected, note positive exposure compensation.

Camera RAW - 15 photos selected, note positive exposure compensation.

Note that these are not photos of an actual piece of art, but of a 1 euro reproduction print I bought in a tourist trap in Spain. It’s hanging on a wall in my room, and it came in handy for illustrating this article.

Next, I click Done.

4) In Photoshop, go File>Scripts>Load Files into Stack. Select your images, and make sure to check ‘Attempt to automatically Align Source Images’ and ‘Create Smart Object after loading layers’.

If you have a lot of source images, this process can take a little while. Go make a cup of coffee, pet your cat or sumthin’.

5) When done, go Layer>Smart Objects>Stack Mode>Mean.

The pixels of all the layers will be mean blended, and the noise will be seriously diminished. Taking into account my photos were ISO 6400 originally, they now look great. I now flatten my image (Layer>Flatten Image), clean up any residual noise with Neat Image, apply a transform to straighten up the image, then apply a healthy dose of Filter>Sharpen>Smart Sharpen. The final step is a slight crop, because when handholding for a sequence like this, framing will differ somewhat, and around the edges of the photo there’ll be a margin where there’s more noise, because there are fewer overlapping frames.

Here’s some before / after crops at 100%:

Comparison of 1 original ISO 6400 frame vs stacked, Neat Image + Smart Sharpen result.

Comparison of 1 original ISO 6400 frame vs stacked, Neat Image + Smart Sharpen result.

And here is the final result:

Result of 15 image mean stack

Result of 15 image mean stack

It sounds like a lot of trouble, but once you establish this workflow, it is quite easy. And it can get you those shots that would otherwise be impossible, such as in museums or other low light situations with static subjects, where you prefer not to use, or cant use, a flash or a tripod.

If you think this sounds like to much work, here’s an idea for a $1 camera stabilizer.



Happy Halloween!

Joshua Hoffine

Happy Halloween! Photo: Joshua Hoffine


One month with Imaging Professional

Dear readers,

Our first month is complete here at Imaging Pro, and I wanted to thank you all for visiting.

We’ve had 663 visitors since sep 25. and I think that is a good start.

The most popular posts has been the Vincent Laforet 5D Mark II video article, followed by Adobe announces Creative Suite 4 and Tineye – the image search engine.

There have been 19 posts in 4 categories, with 86 tags and 13 comments during the last month, and the busiest day were september 26th with 94 visitors.

If you have ideas or comments to this blog so far, feel free to leave them at this post.

Next month will see the introduction of more original material, including CS4 tutorials.

Again, thanks for stopping by!


Save $39.500 on your next camera

Michael Reichmann of Luminous Landscape has a nack for the odd outlandish and seemingly proposterous claim. His site is very popular, especially amongst landscape photographers, and every time he puts a fantastic story on there, the interweb is ripe with debate and discussion. I bet that’s real good for his site traffic!

Anyway, the claim this time is that its near impossible to tell the difference between a $500 camera, the 15MP Canon G10 pocketcam, and a $40.000 camera, the 39MP Phase One P45 back on a Hasselblad – at prints up to supersize a3 (that is, when shooting a specific target – here a forest landscape – and at base ISO, etc. etc.).

Hard to believe? Well, the whole point of shooting medium format is that you can print really large, and really large is quite a bit larger than a3. So I dont see anything really surprising about this claim. Besides, I for one have deep respect for whatever Michael is saying for various good reasons.

I have occasionally shot with a P45 and a G9, but never thought to compare those two. Apparently, the pocket cams are advancing really fast these days!

Take a look at his article and make up your own mind: Youve got to be kidding!

Camera Raw 5.1, Lightroom 2.1 released

They’re spitting them out faster than I can type…

Adobe has just made Camera Raw 5.1 (Photoshop CS4 only) and Lightroom 2.1 available with added support for the following cameras:

  • Canon 1000D (Digital Rebel XS/EOS Kiss F)
  • Canon 50D
  • Fuji FinePix IS Pro
  • Kodak EasyShare Kodak Z1015 IS
  • Leaf AFi II 6
  • Leaf AFi II 7
  • Leaf Aptus II 6
  • Leaf Aptus II 7
  • Nikon D700
  • Nikon D90
  • Nikon Coolpix P6000
  • Olympus SP-565 UZ
  • Pentax K2000 (K-m)
  • Sigma DP1
  • Sony A900

You’ll notice that this camera list is the same as the one I posted for camera Raw 4.6 for CS3, but these cameras did not make it into CR 5.0 for CS4 before shipping. Now they’re supported.

Go to adobes download page.

The DNG profile editor and the beta color profiles previously mentioned has also been updated.

Strangest camera of the week

Carl Zeiss has recently announced this strange cross-breed of a camera and a spotting scope, the PhotoScope 85 T* FL.

The Carl Zeiss PhotoScope 85 T* FL

The Carl Zeiss PhotoScope 85 T* FL

Intended for sportsshooters, birdwatchers and… private detectives?, this beast features a zoom range of 15-45x (600–1800mm in 35mm equivalence), in one handy camera / lens combination. I’m pretty sure theres a market out there for this one, but to me it just seems… Strange.

Available spring / summer 2009.

Random photograph #3

Mathias Vejerslev

What do I have in common with the great David Lynch? Probably more than I realise, but at the very least both of us have done a commercial stint for Nissan Micra. The strange pattern on 'my' car is supposed to disguise it as a leather handbag - this posed an interesting challenge to portray! There is no artificial light on any of these photos, and the entire shoot took only a couple of hours - postprocessing a bit longer. HDR merge via Photoshop and Photomatix. Click photo for more. Photo: Mathias Vejerslev.

David Lynch Micra commercial on YouTube

Black Silicon the new Orange?

Black silicon is a silicon processing method that was serendipitously discovered by Dr. Eric Mazur at Harvard University in the late 1990s. Basically, by blasting a silicon surface engulfed in sulphur gas, with a powerful laser at short intervals, the surface of the silicon turns black and becomes a tiny forest of evenly spaced micro-spikes. The spikes reflects light between them, preserving about 96-98% of it, instead of reflecting it away into space – thus the black surface.

These properties, and this light efficiency, has a lot of promise in the silicon industry. For instance, it could lead to more efficient solar cells. For digital imaging, the implications are obvious. The scientists claim that their black silicon absorbs between 100-500 times the light of a standard silicon chip. – Though only about a 100% increase in the visible light spectrum.

Based on this promise, the team of scientists at Harvard has announced a new company, SiOnyx, with the aim of commercializing this potential. It seems their first market is night vision systems.

Obviously, there is a lot of room for improvement still in the digital camera / silicon chip industry. But there are also many hurdles to overcome for such new technology before it is viable as a fine imaging chip. The future remains elusive.

From New York Times

Capture One 4 PRO released

Danish company Phase One today released Capture One 4 PRO RAW workflow software. The new version is much speedier than its predecessor, and among the new features are:

  • Custom tool tabs
  • Enhanced color editor
  • Styles presets
  • Skin tone tool
  • Lens corrections
  • There’s a lean 30-day demo version available from the website.

    Dont look at the sun…

    We all know not to look at the sun, particularly not through a telelens… I know not to do so by experience, but I’ll leave that story for another day.

    Our star is not only the provider of all the energy available to us, indeed the provider of all life as we know it, it also represents the photo in photograph.

    A transit of the Moon across the face of the Sun, as seen by the STEREO sattelite (NASA/STEREO)

    A transit of the Moon across the face of the Sun, as seen by the STEREO sattelite (NASA/STEREO)

    Boston Globe’s The Big Picture has a feature on this remarkable star. (It’s safe to look at pictures).

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