HDR and Layering updates

For those of you looking for more information about creating Layers to make an HDR image, I came across this tutorial and thought it was pretty clear -- w/a little effort you can translate the main ideas (layer masks) to GIMP if needed.


http://digital-photography-school.com/hdr-style-results-using-layers-in-photoshop

Enjoy!

MCLA Snow Day, and Building Your Own Recipe for Success

Students, I hope you've enjoyed the snow day and had a chance for some r&r or maybe catching up on things. Did anyone make a snowman? It's the perfect snow for it! I shovelled a lot. And went skiing, a lot. And then shovelled much, much more. Here's a collaborative photo: pics taken by my wife Laura, and then processed by me into the double-exposure that you see here... yup, that's me skiing the trees early this morning in the middle of the storm.

It was some seriously fantastic skiing this morning. 18" of fresh powder will do that!

I said if we had a snow day I'd post something here for you. It's about building your own recipe for success.

You'll need to check your gmail documents. You'll find a new shared pdf document there, which is really just a chart. The top lists the five or six software processes that I find myself doing with almost every photo, in order. Then there's a bunch of blank spots -- here you'd record what you've done to a photo, as you work on it. The idea is to be able to keep track of what you do as you process a picture. In other words, write out your own recipe for processing each photo.

As you've seen, once we start using Layers and altering colors and so on, it gets difficult to remember what you've just done to an image, or even why. So it's a great idea to write down what you do as you do it. Seriously, it helps immensely. You don't have to be absolutely detailed (don't record every click of the mouse -- just the important major steps along the way).

And if you really mess up an image, with a good recipe list you can track where you messed it up. Then you can go back to the original image file, redo the steps that worked, and edit out the ones that didn't (because you do have the original image file, right? You did save a copy of the file right away as the "working" file, the one you process, didn't you?)

Another benefit is that if you find a series of steps that typically works for you, by keeping track of them, you can apply them to a different image, or even automate the editing process across a batch of images all at once. For example if you need to reduce any noise, it's important to do so BEFORE sharpening anything in the image -- otherwise you're just sharpening a bunch of the noise. You'll recognize these kinds of tricks if you keep track of what you do. And anyway, if you have to create a series of thirty or more images all at the same proportion and file size, say for a final book project for a photo class taught by a skier, then you're prepared by keeping organized as you work. (hint!)


Reminder: have you backed up your images this week?

Blinkies, Crunges, the Histogram and HDR

Winking is cute. Winking is sassy. Winking is fun. If you wink with both eyes it’s called a double-barreled wink, or blink. Blinking your eyes takes about 1/100^th of a second – the same time that makes one skier a gold medalist and another only a blink behind, a loser, mere hundredths of a second. And in photography, a recurring case of the blinkies usually isn’t cute, isn’t sassy, and isn’t fun. It’s a blindspot. A blinkie is a highlight that’s just way too bright and washes everything else out. It is a flat bright spot, that ruins the illusion of sculptural form, the subtle tonality needed to create the sense of roundness.

The reverse of a blinkie is what I call the crunge: a super-dark and big shadow region in which there is just dank darkness, no detail, no form. It’s a problem because if you try to print a photo that has a serious crunge then you use up all your printer ink extremely fast, and that burns money. And anyway, it looks like a big flat dark area, kind of boring. Crunges suck. Blinkies suck. Neither one provides you with a wide range of delicate values and hues between absolute white and darkest dark.

In most cases, photos are better when they include a full range of luminosity from very dark to very bright w/many thousands of subtle values between them – the full range is the gold standard of exposure control. To describe it, photographers also use the jargon ‘low key’ (a mainly dark composition), ‘middle key’, and ‘high key’ (a mainly light composition). In each case we don’t want blown-out highlights or shadows. So, how do you avoid the blinkies and the crunges?

First some examples. Maybe you’ve taken a photo like this:

This has serious blinkies. The snow is washed out, and the sky in the upper right is totally gone. 

And here’s the dreaded crunge:

Oof! That hurts my pocketbook just looking at it and thinking about printing it! Here’s the correctly exposed version that has a nice deep dark range and serious, lovely details – a good low-key image:

(If you clicked on the Mt. greylock image you'll see a big problem... wind made my tripod shiver!) (But the exposure is correct and not full of crunge.)

The secret to knowing what to do about blinkies and crunges is first to make sure that you can see them while you’re shooting. To do this, if your camera has a highlight warning function, then turn it on. It’s usually in the camera’s playback menu, or a submenu of the playback menu. So now we’re going to break a cardinal rule and edit on the basis of our image in the camera’s LCD screen. We’re not editing for sharpness, just for over-exposure. If the warning’s on then when you view your image in the camera’s LCD screen, your camera will let you know if any highlights are washed out by blinking sections of the image that are blown-out highlights. It looks like this on the back of my camera:

The screen will blink the highlights from the negative image on the top to the image below – sort of like a strobe light – so that the display shows an immediate exposure problem in a lot of the lights in the image. Thus the highlight alert or highlight warning function can save you a lot of trouble. Use it if you have it.

If you see blinkies then the easiest thing to do is to reshoot the scene, underexposing the image enough that the highlights aren’t too hot – use the +/- button and scroll wheel to adjust the exposure (or whatever controls are available to you to adjust the exposure). You can also experiment and see if you get more blinkies by purposely overexposing the image. Here is the overexposed version of the landscape shown in the LCD screen above (left), next to the stopped-down version (right) which is a very close representation of the snowy, cloudy day at North Pond in Savoy State Forest:

And yes, I took these photos to demonstrate the blinkies for you. Blinkies happen a lot in winter, because exposures are very hard to do when there’s snow. When they sense a lot of light grey tones, most digital cameras try to overcompensate the lights when they are set for automatic exposures (some cameras now have a ‘snow’ or ‘winter’ setting). In this case – a cloudy moment in the middle of a light snowfall, the visual mood was soft and sort of dark, definitely what’s called a ‘middle key’ scene. In real life it didn’t have any bright highlights. The overexposed image almost looks like a bright sunny day in comparison!

But if you have no manual exposure control – no +/- button to mess around with – then what do you do? Try reshooting the scene from a slightly different angle, turning every so slightly away from the highlight. Sometimes this works great. If your camera has spot metering, set it to spot meter so that you can select the exact point where the light meter reads the scene, instead of letting the camera automatically meter an average of the entire scene. You might also be dealing with the kind of camera that has a variety of settings for ‘scenes’ or ‘camera modes.’ Try selecting a different camera mode, for example, using the portrait setting even if you’re making a landscape photo.

Using software you can analyze your photos in many ways, first among them is using your Histogram (gesundheit!) Sounds like a weird allergy medicine doesn’t it? Have a bad case of the blinkies, or a serious bout of crunge? Then take one Histogram and call me in the morning. Some cameras will allow you to check an image’s histogram on the LCD screen. Some cameras won’t. But most image processing software will show you the histogram.

Here’s what the histogram of the good exposure of the scene above looks like in Photoshop:

In GIMP it looks quite similar (see menu Windows -> Dockable Dialogs -> Histogram).

The Histogram is a chart. It shows you how many pixels in your image are at each level of luminance – in other words, how much light and grey and dark you have in your image. It represents the darkest values on the left, and midtones in the middle, and the lightest values (highlights) on the far right. If you have a full tonal range, then you’ll see some pixels across the entire histogram. This chart shows an o.k. distribution, with no bright highlights, and a lot of middle light gray values. Here’s a comparison:

The histogram changes depending on the distribution of luminosity, which is sometimes called value or brightness. The histogram also shows you clues about how you’ve organized your composition – what value and color ranges your image includes. A primarily dark image (called ‘low key’) will have most of the histogram grouped to the left, whereas a mainly light image (called ‘high key’) will have most of the graph grouped to the right. A good distribution in either case will have some height across most of the entire graph.

Now for the fun part: Suppose you have an image that needs a little exposure adjustment – maybe it’s just a tad too light or too dark.

To fix this, use the LEVELS adjustment (In Photoshop, it’s under menu Image -> Adjustments -> Levels; in GIMP it’s menu Colors -> Levels). Here’s what the Levels Control looks like in Photoshop:

See the histogram? You’ll find that you can stretch or compress the histogram by adjusting the input and output levels. Normally I leave the left and right inputs at 0 and 255, and for many landscape images, adjust the centerpoint to somewhere between 0.95 and 0.88 – try it out on one of your own images and you’ll see how your exposures change. If you’d like full details about how this works, then read the HELP file for Photoshop or GIMP. The main point is that you can, if you need to, make exposure adjustments by using the Levels control. As with all adjustments, try to be subtle not crass.

[If you don't need to see a histogram, then in Photoshop you could instead alter the exposure using the menu Image --> Adjustments --> Exposure. This will give you the ability to 'gamma correct' in addition to altering the overall exposure. ]

Of course if you’re starting with a good exposure, you’ll only need a very small adjustment, perhaps no adjustment at all. Finding the best exposures requires that you read the image, on your computer screen and then if you’re going to print it, in the print. Often what looks great onscreen looks too light or too dark in print, even if your screen, file and printer are all calibrated together. So, don’t just look at the histogram… read the image and compare/contrast with the histogram.  

(Exposure Hint: since you know about using Layers, why not make a duplicate layer of your photo, adjust the LEVELS in it, and then use the layer blending options to make subtle adjustments? You could also combine a moderate exposure and an overexposed image to get more detail in the middle grey ranges.)

Finally, there’s one more strategy that can help you avoid the blinkies and the crunges: if possible, always take a set of bracketed exposure of every image. It won’t always be possible… some images are fleeting, moving by far too quickly. But many scenes are relatively still. If you can set your camera to take what it thinks is a good exposure, take it, and then set it to take a few progressively under-exposed and over-exposed images. Then when you’re back at the computer you can upload all five or six exposures, combine the best ones using Layers. You can get many effects by altering the layer controls for opacity/transparency, and blending style (instead of ‘Normal’ try ‘Lighten’ and ‘Darken’). It’s a bit complex but using layers and a variety of bracketed exposures you can build a histogram that shows a wide and full range of luminosity across the entire gamut of light to dark. This is something that you can do with digital photography that’s extremely difficult with wet photography.

And yes, you can do this in an automated way if you want to – it’s called tone-mapping, or, the High Dynamic Range (HDR) image. Wink! Here’s a set of links you can read to learn how to make an HDR image, and why it’s useful:

The ultimate guide to HDR Photography, at Photocritic Blog – probably the best post on the topic, with lots of good links.

Some great HDR images, such as this one of a cathedral, at HDR Crème

Flickr How-to HDR group


That's it! Now go test and find out if you're camera has a highlight warning function, check out the histograms of some of your photos to find some that have great luminosity distributions, and maybe try to make a couple of HDR images... it'll take some practice, but the results can give you a wide array of values across the entire histogram. Here's an example from me: a still life, 'Fantasia'

 

Check out the dark orange shadows underneath Medusa's head -- that's pure, subtle HDR at work. 

Multiple Exposures Online

Just as a followup to our in-class project... some examples of multiple exposure photography online.

You can see what each of you submitted to our online folder at
http://picasaweb.google.com/Studio.Gregory/MCLAPhoto2010SubmitFolder?feat=directlink
A few of you have made comments... good work all, many delightful images.

I liked this set of tips and tricks -- similar to Alex's photo of himself -- Seven Steps to Taking Clone Photographs by Michael Zhang.

There's also many multiple exposure images throughout this online set, from a variety of different photographers on the time-worn theme of The One Who Got Away at Pictory Magazine.

Wintery Weather

Hundreds of Great Photo Tips from Pro Photographers

There's a lot of really great ideas at this blog post:

225 Tips to Inspire You

Do these photographers' ideas apply to the kinds of photo you'd like to do?

What tips did you find that seemed helpful to you?

Improve Signal, Reduce Noise

Grainy versus Smooth: How to Reduce Noise in Digital Photos

Noise is Horror

[image courtesy of Poltergeist, a Spielberg Production, 1982]

Poor Carol Anne, the little girl sucked into the static of a demon-possessed tv... it is the worst of image noise, the kind we digital photographers would like to avoid.   


A Brief Personal History of Static

Many years ago, before cell-phones and before iPods, while driving across Wyoming I stopped at a wayside for a much-needed break. And promptly locked my keys in the car. This wouldn’t’ve been such a horrible problem if Wyoming weren’t so darned big! I called the state police: they were many hours away and had a policy of not helping locked-out drivers (‘Too bad you had your windows closed’ said the operator, and ‘well, here in Wyoming you might just have to break in.’) I called the nearest town service station – 130 miles away. The earliest they could arrive would be four hours. I walked around and waited, and waited, and waited. I tried listening to my Walkman’s radio, but I was so far away from the civilized world that it too was out of the range of radio stations. This meant I could listen to a symphony of static.  

Static is caused by many things – loss of radio signal, occasional solar flares, or just poor electrical equipment. If you ever have the chance to listen to some static, about ten percent of the noise is caused by the world around us, and another percent is caused by the radio itself. A tiny portion of radio static is in fact one of the great scientific discoveries of the 20^th Century. Radio astronomers Arno Penzias and Robert Wilson at first thought the noise they experienced in their radio telescope was residual interference from nearby New York City. It wasn’t. They checked their equipment, and after much testing, figured out that a small slice of the noise was the universe itself – what today is known as ‘cosmic microwave background radiation’ (CMBR). Its existence is evidence that the universe is billions of years old and resulted from the Big Bang – a tiny bit of the static is waves and ripples streaming through space, caused by a great and distant explosion. Penzias and Wilson won the Nobel Prize for figuring out how to precisely measure CMBR, figuring out exactly what was the universe making noise, what was their radio equipment. Since then, radio telescopes have been greatly refined and have extremely fine sensitivity and very high signal-to-noise ratios, so that they can discern the most distant sources of radio waves in the universe. So, sitting in Wyoming, all was not lost and I could try to imagine what portion of my Walkman’s static was not merely static, but instead a faint signal from the universe 13.7 billion years ago.  Finally the tow truck arrived, the service man jimmied my car open, I paid him a hefty fee, and have forever kept a spare car key in my wallet.  

                It turns out that just like a radio signal received by a Walkman, all electronic equipment is subject to some noise. Digital cameras are no exception to this rule. When you search for a radio station that you can listen to, you are searching for a strong signal – strong enough that the small amount of noise caused by your radio equipment is overwhelmed and thus, not noticeable. If you take a photo in low-light settings, when you have a hard time getting a clear visual signal, then you’re camera will record a noisy, grainy image. It’s static at it’s finest. Noise is the opposite of Signal. What’s Signal? It is the information, the data, that your camera’s light sensor records – the light that moves through the lens and hits the camera’s sensor. In any electrical device we talk about the “Signal-to-Noise Ratio.” In other words, to get a digital photo that is less noisy (and thus sharper, smoother, and less grainy), we need to figure out how to increase the Signal.

                Noise is increased whenever you lose the Signal. In digital photography, you can lose the signal in many ways, such as leaving the lens cap on (no light), to selecting the wrong exposure for a low-light setting. A low-signal digital photo will look noisy like this:

This is a photo of Luna, who was being very patient with me. And this is a crummy photo full of colorful static – noise. My camera tried really hard to make a good image, my model was very forgiving and willing to sit still, but there just wasn’t enough signal. There’s nothing that can be done to rescue this dismal photo.

Here’s a much, much, much better photo that was made from a very clear signal: 

The lighting was good, the camera settings were correct, and thus sharpness and focus were good. And as always Luna got a little tired of me fiddling around with camera settings – she fell asleep.  The fact remains that this is a good photo, and with image processing software, you can do just about anything with it.

Some artists use graininess on purpose. I think you’re better off shooting a smooth, sharp photo and then using an ‘add noise’ filter if you would like a grainy look. The problem is that it’s darned difficult to remove noise from an image, in the same way that it’s impossible to sharpen a poorly focused image and make it focused. So, we start with low noise and perfect focus, and then alter the noisiness and blurring in an image editing program if needed.

How to Reduce the Noise in Your Images

-          Start with a good Signal.

o   Great photos begin with good lighting matched to your camera’s settings and capabilities. Some cameras are just more noisy than others – most cameras have a couple of settings where everything works well to produce low-noise, high-signal images. Experiment to find out what kinds of images produce good signal for your camera.

-          Check Your ISO Settings.

o   an ISO setting of 100 is usually the best. For digital photography, ISO is a ratio of how sensitive your camera is to light – set it higher and higher and the ratio changes. The higher the ISO, the more sensitive to light, and the more overwhelming the noise becomes. Even the best digital SLR cameras at ISO settings about 1600 produce a lot of noise.

o   Some scenes require higher ISO settings. Aim for 100, but alter it up to 400, 800, or 1000 if you know you need to because you are working in lower-light settings, etc.

-          Know Your Lighting

o   Where is the light source? Is there a lot of light or are you in a low-light setting?

o   If you’re in a low-light setting, can you add some light? (use a reflector, flashlight, or flash?)

-          Use the ‘reduce noise’ filter in an image processing program. Try it out and see what happens – but be warned that too much of the filter will make your photo blurry.

o   In Photoshop, it’s under menu Filter:Noise:Reduce Noise

o   In GIMP, it’s under menu Filters: Enhance: Despeckle

o   In Photoscape, Filter: Noise Reduction (Clear Skin): select High, medium, low.

o   Consider trying ‘Noise Ninja’ – this is not a free program – but it is awesomely useful. You could get it as a standalone program or a Photoshop plug-in at  http://www.picturecode.com/index.htm You can download a free trial version that will show you what it can do, but won’t let you save images. At the very least you can read the company’s description of noise in digital imaging at http://www.picturecode.com/noise.htm

-           Reshoot. It’s possible to take a variety of photos of the same scene, and then combine them to reduce noise. This is an advanced topic that we’ll look at later.

 

For more information, read this link: http://digital-photography-school.com/photography-1017-iso

Bonus: Artists Tom Moody and Ray Rapp have made photos of static into fine art: http://www.digitalmediatree.com/tommoody/photoinst/statphotos/