What colour is snow?

Winter sunset (Tokina11-16 @1/50s, f6.3)
Winter sunset (Tokina11-16 @1/50s, f6.3)

Click here for larger image (1200×800, opens in new window).

In most images snow is either white or a high neutral grey. Makes sense… snow is white, right?

Snow takes on the colour of the light shining on it. Most of the time, that colour is negligible, but at dawn and dusk (or in the shade during high sun) snow takes on definite pastel shades, usually pinks, yellows and cyans (‘baby blues’).

I often give snow a colour. The viewer mentally assumes snow is white and fails to notice the colouration. Instead, they unknowingly take in the pastel shade and assume the ambient light is that colour. The colour of this light tends to promote an emotional ambience, so our snow tinting is a quick shortcut to imply that most difficult of things; mood.

In the image, I’ve left the snow tinted cyan. Mostly to show we are in shade (we are looking up the shaded side of a short hill) , but also partly to retain a feeling of extreme cold, and partly to contrast with the oranges of the setting sun.

Until you read the paragraph above, I bet you would have sworn the snow was a neutral grey (white darkened by being in the shade), and by implication assume that the camera is in a very cold and quiet shade. Look back at the image and my trick becomes obvious; the feeling of coldness is enhanced by the implication of the local ambient being towards cyan.

I know some photographers would complain about the image, saying it looks a little unnatural to them; snow is white. I have no problem with that (and would do the same for a shot in direct high sun), but I would advise against blindly setting white point with reference to what you think should be a neutral white if the affected hue is widespread in your image and caused by natural light. Doing so may inadvertantly kill the ambient light colour. This is especially true in winter photography where although the scene  may be predominantly tonal (blacks, whites, greys, slate blues and earth browns) it is the ambient light that actually gives you colour.

Image shot with Tokina11-16, at 12mm, 1/50s f6.3, hand held and pointing down at the near-middle distance.

Post processing (using Lightroom): original snow tint retained by setting the colour temperature low (9500… for the snow to be ‘corrected’ back to white, the white point would be set to 11000). Ice tinted yellow (using adjustment brush) to differentiate it from the snow and to exaggerate the implied sky hues. Trees and foliage lightened slightly by adding exposure (again using adjustment brush). Reduced overall image exposure 1 stop to deepen colour of the sunset (from yellow to orange – this also darkens the snow, enhances the feeling of shade, and makes the snow tint a little deeper). 10% crop for aesthetics (removed sky at top to maintain a subdued overall key, cropped slightly from the right to make the fallen log point more to the centre). NB – Usually with snow, its more normal to increase the exposure by 1.5-2.0 stops rather than decrease it, because left to its own devices, a typical camera will try to make snow a grey corresponding to a 12-18% reflective grey, depending on your camera model (but usually closer to 12%, which incidentally, is why I never use a 18% grey card!), but in this shot, darker snow is ok because I want to emphasize the fact we are in shade.

Autumn’s end

Autumn's end
Autumn's end

Click here for larger image (aprox 1400×900, opens in new window)

We’ve just had the earliest snow in years. Autumn has been shunted straight into winter, and I was out the back looking for an image to reflect this.

I found the leaf in a frozen bucket. I prised out the ice in one piece. My intention was to position the ice up to the sun with the ‘water side’ facing the camera. This would hopefully simulate the view of the ice from underwater, looking up to the sky.

Sony Alpha a500, Tamron AF 90/f2.8 Di Macro at f20 (the ice was pretty thick and for this to work absolutely everything had to be in focus, hence the large f-number). 5 exposures 1EV apart. Post processing: combined into a HDR image using Nik HDR EFEX Pro, slight desaturation post HDR via Lightroom, no crop.

Update Jan 2011

I’ve never really been happy with the original (too cold). Here’s another version, where I’ve made good use of HDR EFEX Pro’s UPoints to give a warmer interpretation. If nothing else, it gives a good indication of the power of NiK UPoints when used in creative HDR.

Larger image here, adjusted slightly to make it suitable as a desktop wallpaper (2.7Mb, 1920×1280).

Autumn's End 2
Autumn's End 2

Wide angle and hyperfocal distance

November sunset
November sunset

As a quick rule of thumb, if you put the Tokina 11-16’s lens hood on, set the camera mode to M (manual) and turn the focusing to the absolute minimum (left as far as it will go), then set the f-number as far right as you can go (f22), then everything from the end of the hood onward will be in focus.

Have a closer look at the image above. Note that everything is in focus apart from a little yellow leaf in the bottom left corner; this leaf is not in focus as it was actually touching the lens glass.

All the other leaves at the bottom of the image are close to the end of the standard lens hood that comes with the Tokina 11-16, putting them around 4cm away from the front glass, and in sharp focus. Pretty cool, and something you’d expect of a macro (especially when the normal closest focusing distance of the Tokina11-16 is twice this distance), until you notice that everything else beyond the first row of leaves and up until the far trees is also in sharp focus.  The lens has everything in sharp focus from 4cm to infinity!

A macro lens can’t have that massive depth of view. A wide angle lens can’t do this either… unless you know about hyperfocal distance.

Hyperfocal distance is pretty easy to define. It is the focal length and f-stop combination that gives you the maximum depth of field. It is only really useful at the low end (below about 25mm), and is particularly useful for wide angle lenses when used for landscape photography. It is the trick behind the standard ‘small smooth pebbles shot close-up on a beach, but with the sea and sunset behind them in perfect focus’ cheese shot.

Older lenses had what amounts to the hyperfocal distances etched on the focusing ring, but with auto-focusing, the practice has all but died out. The trouble with auto-focusing is that it concentrates more on getting the thing you are pointing at in sharp focus, at the detriment of everything else. This strategy works well for everything except landscape (especially wide angle), where you may have something very close to the lens, but you also want distant scenery to be sharp. The good news is that you can generate the hyperfocal distances yourself.

I won’t bore you with the maths (as I’ve done it for you) or the theory (because you just want to take pictures), but will instead show you the quickest way to get going with hyperfocal distance, assuming you have a Tokina11-16 (For those with a wide angle other than the Tokina 11-16, you can form your own chart via http://www.panohelp.com/hyperfocaldistance.html).

  • The table below is the hyperfocal distance chart for a Tokina11-16, set at 11mm. Normally you would have a different chart for each possible focal length, but nobody uses the Tokina at anything other than 11mm for landscape photography, right? Click this chart to get a full size image in a new browser. Print the image.
tokina11-16 hyperfocal chart
tokina11-16 hyperfocal chart
  • Laminate the chart (or cover the printout with Sellotape on both sides and then cut the chart out). Keep this chart in your camera bag whenever you take the Tokina11-16 out for landscape shots. There are two charts. One is in feet, the other is metres. Take your pick (and sorry about the spelling; it is correct but only in the Queen’s English).
  • If you want to create an image that includes a subject very close to the viewer (such as a flower, etc), but that also needs the background to stay in focus to infinity, you need to find the distance the subject will be away from the centre of the Tokina (or from the front lens of the Tokina if you want to be a bit more conservative)in the h/2 column. Read off the corresponding hyperfocal distance h and f-number, and with the camera in manual focusing mode and aperture priority, set the corresponding f-number at the camera, and enter the hyperfocal distance h as the focusing distance on the Tokina11-16. There, you’re all set up.

As a quick rule of thumb, if you put the Tokina’s lens hood on, set the camera mode to M (manual) and turn the focusing to the absolute minimum (left as far as it will go), then set the f-number as far right as you can go (f22), then everything from the end of the hood onward will be in focus. Although you may be unused to having your camera in manual mode, this is nothing to worry about, because your lens is now set with such a wide depth of focus that everything will be in focus. The downside of course is that you have such a small aperture that you will not be able to catch fast movement (but the lens is set up for landscape shots, so speed doesn’t really matter).

I like to stop up a little more than the minimum; for the image above I used the f18 column on the metre chart.

For those interested in my shot, it is a HDR image (12 exposures, 1EV apart), and is the background layer for another work (the final piece extends further at the bottom of the current image to show a cross section of the earth below, where we see an acorn under the ground). Yeah, I know. Cheese shot.

Peace lily

Peace lily (Spathiphyllum)
Peace lily (Spathiphyllum)

Click here for larger image (1280×850, opens in new window)

Too cold to go out, but shot this at home late at night. Loving the effect that HDRI makes to images taken in low light; looks almost like an airbrushed illustration. The background is not a Photoshop texture. It is my living room wall, currently partway through redecoration (although it is giving me so many photo opportunities that I’m considering leaving it that way!). 

HDR: 6 exposures 1EV apart, tone mapped with Nik Efex Pro (as a plugin for Lightroom).

Flash Review: Photomatix vs Nik HDR EFEX Pro vs Photoshop CS5.

Review updated and conclusions significantly revised 6Nov 2010; original review was overly critical of Nik EFEX, but the issue was almost certainly due to my own camera work!

Autumn is the time of low, cold bright suns. Those suns make a perfect subject for evaluating a number of HDRI (High Dynamic Range Imaging) applications.

Last week, I drove around the Peak district (UK) whilst taking a large number of shots directly into the autumn sun. I then reconstructed the shots as tone-mapped images using three different applications;

  • Photomatix Pro
  • Nik HDR EFEX Pro
  • Photoshop CS5

I present the results of my trial below (as well as a few other test shots) as a flash review consisting of brief pro/con bullet points. The review is aimed at existing HDRI users, and I have kept it to brief bullet points under the assumption that you know the issues in HDRI, and standard HDR photography work flow. In fact, you probably only really want to know how good the just-released Nik HDR EFEX Pro is vs existing solutions, and want some insight regarding whether it is worth changing over to it.

The images below are shot to test particular important features of HDRI, as noted in the descriptions;

high autumn sun 01
high autumn sun 01

‘High autumn sun 01’ was shot with the camera on the ground using three exposures 0.7EV apart. The sun is to the  upper right in clear air, and is actually too bright to look at. The challenge here for HDRI software is threefold;

  • To ensure that the direct sun does not white out the sky
  • To give some detail back to the road in the near ground  (as it is out of focus close to the lens).
  • To maintain realistic colour to the road and walls (which would otherwise tend towards bright blue).
high autumn sun 02
high autumn sun 02

‘High autumn sun 02’ was again shot directly at the sun, using three exposures 0.7EV apart. In this shot the big cloud has the sun directly behind it, and appeared a bright white. The camera is hand held, and there is a breeze on the barbed wire. The challenge here for the HDR software is;

  • To remove ghosting in the wire between the three shots, without losing detail in the wire, and without blurring the grass texture around the wire
  • To correctly merge the overall shots without adding motion blur, thus keeping the distant tower and treeline intact
  • To add detail to the cloud surface.

It goes without saying that without HDRI we would see blown out highlights and clipped/banded shadows for both the above images.

Although HDRI can be used to for realism (i.e. to maintain a high dynamic range), it is also often used as a creative tool (enhancing textures and adding custom styling by using nonlinear tone map compression). HDRI can thus be used creatively to add movement or texture. The following two images illustrate examples of this.

Creative HDRI 01: low noon sun
Creative HDRI 01: low noon sun

In this shot, I am pointing at the low sun and trying to control the resulting flare via a circular polariser (i.e I am rotating the flare to ensure the longest streak is oriented with the adjacent tree, and also attempting to get a long diagonal streak top left to bottom right). I am doing this to (hopefully) give the scene a sense of movement. As this scene has a very large tonal range, I exposed across the entire range of the camera (12 exposures 1EV apart).

Issues here are;

  • How easy is it to control unwanted aberrations (chromatic aberration) whilst increasing the ones we want (flare).
  • how well did the application deal with the large number of files (12 4272×2848 images).

For the final image, I am using the fact that our house is currently partway through redecoration. It has bare, stripped walls. I thought it would be nice to bring out the textures of the walls through some extreme HDRI, to give a painterly effect;

Creative HDRI 02; Self portrait with red coat
Creative HDRI 02; Self portrait with red coat

Also, click here to see a larger image of the final composition (1200×800, opens in new window)

The issues here are;

  • Ease in bringing out the textures in the image.
  • Ease of controlling the main subjects of the image (shadow and coat).
  • The composition relies on the lack of colour/texture in the shadow, and how it is offset by the big colour/texture in the coat and cushion either side of it. The intent of the composition therefore relies on the technical ability to control the colour/texture in these three areas independently of each other.
  • Ability to add detail back to areas that would otherwise be blown out (i.e. the arm of the sofa and the bright sunlit areas on the wall)

Image created with 7 exposures 1EV apart.

This image is the only one of the set that is not a HDRI test; it is the only one that I consider to be a finished image. With this in mind its probably worth spending a little more time with this image, by also showing the brightest and darkest source images;

Brightest image
Brightest image
Darkest image
Darkest image
Although I created versions of each image in each application, I have only shown one version of each image (this is after all a flash review!). Tools used per each image are as follows;
  • Image 1: Photomatix and Photoshop (Photomatix used for tone mapping only, Photoshop used for post processing only)
  • Image 2: Photoshop only (i.e. Photoshop tone mapping, and Photoshop post processing)
  • Image 3: Nik EFEX (as a plug-in for Lightroom 3). No post processing in Lightroom.
  • Image 4:Nik EFEX (as a plug-in for Lightroom 3). No post processing in Lightroom.

Photomatix Pro

Good

  • Quick user interface (once you get to grips with it).
  • Very good ghosting and Chromatic aberration reduction algorithms.
  • The HDR tool of choice for many well known HDR photographers. Practically the industry standard in HDR creation (up to now).
  • Although the manufacturer’s instructions are a little obscure, there are a few good books that concentrate almost entirely on Photomatix.  I recommend Practical HDR by David Nightingale, the best of the several books on the subject that I own.
  • Dedicated batch processing

Bad

  • Interface is initially very daunting for beginners.
  • Clearly written by programmers rather than photographers; some of the sliders are inter-related (e.g. you have to vary the gamma value after moving many of the main sliders, but this is not made obvious. This leads to a very large learning curve before you stop ‘just guessing’ and begin knowing what each control actually does.
  • No advanced features such as curves or post tone-mapping contrast control. This means that you need Photomatix and another application (typically Photoshop or Lightroom/Aperture) to complete your tone-mapped images.
  • Poor image zoom controls.

Nik HDR Efex Pro

Good

  • Shortest learning curve of all the available options.
  • Nik have clearly learned from and fixed Photomatix’s inter-related sliders. All sliders in EFEX are easy to understand and show little inter-relationship.
  • Full featured enough for advanced users, and has almost everything you need in a single UI.
  • Brilliant, well thought out UI.
  • The ‘UPoint’ Technology is a godsend for quickly spot-editing the HDR image without having to set up adjustment layers (Photoshop) or Adjustment brush areas (Lightroom). Even better, it allows you to adjust before tone-mapping so you maintain dynamic range.

Bad

  • When you save, the whole HDR image is tone mapped and re-exported as a bitmap. This means that you lose all your settings, which is not too bad as you can save your slider settings as a user preset… but you also lose your UPoints! Ouch! An option to save the HDR file and UPoints might have made sense for pro users and professional photographers (who might have to tweak a complex image tone-map for the client, etc).
  • Overuse of UPoints can sometimes introduce glow fringes (especially around trees or other complex objects) when you change the tone of the surrounding sky). This is caused by the UPoints and NOT tone mapping halos.
  • Although the plug-in controls chromatic aberration (and usually does it well) you have no direct control of it. Nik EFEX generally tends to take control of many things behind the scenes, and this may be seen as a bad point for some users.
  • Seems a little buggy when used as a plug-in for Photoshop CS5 (update; seems to crash occasionally if you do not load the exposures into PhotoShop CS5 before invoking Nik HDR EFEX… if you load the images first, it seems ok).
  • Limited batch processing (you would be typically relying on Photoshop batch processing instead).

It is worth noting that althoughNik HDR Efex Pro is a plug-in and no shortcut is added to run it as a standalone, it does seem to works as a standalone if you run the executable file in the install directory (Program files > Nik Software > HDR Efex Pro > HDR Efex Pro.exe)

Photoshop CS5

Good

  • HDR features massively improved since Previous versions of Photoshop.
  • HDR features free if you use Photoshop CS5 anyway (and if you are serious in Digital Photography, you probably own PhotoShop already).
  • Cheap if you already own a previous version of Photoshop and upgrade to CS5
  • Allows you to do (or fake) most of the things that the other solutions allow, assuming you know Photoshop well.
  • The fact that it allows you to save the 32 bit HDR file (and use non destructive editing) means that you can save (and later edit) intermediate steps in your project.
  • The default settings tend to give very acceptable realistic HDRI images.

Bad

  • Requires a very good understanding of Photoshop to use well.
  • Tone mapping options a little limited when compared to other solutions.
  • Expensive if you have to buy Photoshop CS5 (i.e. without upgrading), and certainly not worth it if you are doing it for HDRI only.
  • Although Photoshop allows you to create a 32 bit HDR file, there’s almost no editing you can do with it without first tone mapping it first. In particular, none of the filters or dodge/burn work with a 32 bit file.
  • Takes longer than either of the other two options (longer, more complex work-flow).
  • Can produce massive files (and therefore requires beefy hardware)

Results

Best use of each application;

Photoshop only: When you want to create a realistic image (i.e. when you don’t want to make it obvious that HDRI is being used).
Photomatix and Photoshop: Best tool to use when you have a difficult set of images.
Nik efex: Best general purpose HDRI tool overall. Best tool to use if you have Lightroom but not Photoshop.

For these results, I’m looking for failures that would stop the image being accepted as stock photography on technical grounds.

For the first image, all three applications did well. Surprisingly, all three applications produced good results very quickly, with Nik EFEX being by far the fastest. Photomatix required curve enhancements in Photoshop.

For the second image, PhotoShop would have failed as it could not fix the movement on the wire. I had to add the wire in manually via layers/clone tools to give acceptable results, and that took an extra 20 minutes.

For the third and fourth images, there was one outright winner: Nik EFEX. Only this application gave me the level of control (via UPoints) needed to control specific areas of the images. For example, the last image was less effective in either Photoshop or Photomatix, because I could not enhance the shadow and coat separately whilst still in the tone mapping process. Photoshop CS5 comes close, but all the close editing has to be done after the tone mapping, and you can therefore lose  tonal range (the coat came out blown out in Photoshop whatever I did).

Fora ll three applications, a multi-core processor was seen to peak at 100%, proving all three applications are multi-core aware. However with large (or many) files, hard drive speed seemed to be the real bottleneck.

Conclusion

My current HDRI work-flow uses Photomatix and Photoshop together.  I really wanted to like and move over to Nik HDR EFEX Pro, lose Photomatix, and stop having to post edit my tone maps in Photoshop/Lightroom. An almost impossible task, but Nik HDR EFEX does it.

The only downside to Nik EFEX are;

  • You don’t get quite the same level of import control as Photomatix/Photoshop (albeit this is often better for work-flow; I have only seen Nik EFEX get it wrong once in about 50 or so images!).
  • You can’t save intermediate states as you can in Photoshop. This means that once you save, you cannot easily tweak the image without running through the entire tone mapping process again.
  • Although Nik EFEX is ideal for beginners in HDRI, the instruction pdf only tells you how to use the application. Some indication on how to actually photograph for HDRI would have been appropriate. This means that if you are new to HDRI, you will definitely need a HDRI book (but of course, non of them yet cover Nik EFEX). Catch 22.

Bottom line

The work-flow improvements created by Nik HDR EFEX Pro are substantial, but you do lose a little control at the same time. Although Nik EFEX is great for about 90% of my HDRI images, I’m still finding that I need Photomatix for about 10% of them, and this is mainly where the image has large amounts of Chromatic aberration (Photomatix seems a bit better for this).

Best use of each application;

  • Photoshop only: When you want to create a realistic image (i.e. when you don’t want to make it obvious that HDRI is being used). Also useful to tone down a HDRI image by merging it with one of the original exposures (this is a common trick I use, and I need Photoshop to do this whatever the HDRI application I used). Best tool to use when you are prepared to spend a long time on your image (you can emulate most effects in Photoshop, given enough time and/or Photoshop skill). Photoshop also creates the most realistic (true to life) images, but on the flip side, it also gives least ability for creative tone mapping.
  • Photomatix and Photoshop: Best tool to use when you have a difficult set of images, e.g large amounts of chromatic aberration. Also well respected in the HDRI community, with lots of literature on best use (almost all HDRI books cover it).
  • Nik efex: Best general purpose  HDRI tool overall. Best tool for creative use of HDRI. Best tool for new entrants into HDRI, because of it’s ease of use. Best tool to use if you have Lightroom but not Photoshop.