What’s Your Preference?

Mike Sperlak · #1 (**permalink**) 01-17-2012, 03:57 PM

HDR (High Dynamic Range) Tutorial
(Note: View the tutorial on my site with screenshots for every step if you have trouble following along: HDR Tutorial)

Hi guys, My name is Mike and I enjoy long walks on the beach (with my camera) and puppies. I also want to share with you my workflow with HDR images in depth.

Have you ever wondered why, when you take a picture of the sunset on your camera, that the foreground is so dark and the sky still looks a bit dull? How about a great foreground, but the sky is all white? What about when shooting indoors and the windows are all white? This is because the sensor on your camera can only pick up a certain luminance (light) range. It's like how when you step outside in full sun you can see everything just about perfectly, but you can also step out into starlight and see pretty well too (if you've eaten your carrots.) The amount of light you see on a moonless night is 1/1,000,000,000 of the light you see at noon. Yet, we can see both fairly well. Your typical outdoor scene consists of about 14-18 stops of dynamic range. (luminance/dynamic range is just the range of luminance values from light to dark, if everything is pretty bright or dark there is low dynamic range, if there are dark shadows and bright highlights, it has high dynamic range.) Your eye, without adjusting for light/dark scenes, can see about 17 stops. If you measure the range of light overall your eye can see, it is about 30(!) stops. Unfortunately, most point and shoot cameras can only discern about 10-12 stops of dynamic range. Modern DSLRs are between 11-14. My beloved 5DMKII has about 12, and much to my dismay his arch rival the Nikon D3X has almost 14. One point to Nikon.

So what to do? Contrast looks good in images, so maybe you don't need to do anything. It's ok if you have some shadow detail clipped or highlights blown out. Plenty of awesome pictures are highly clipped or blownout. But sometimes you want those awesome colors to pop in the sky, and see your foreground subject at sunset. this takes us to....

HDR Imaging

High Dynamic Range (HDR) is a technique to use when you have dynamic range in a scene that is much greater than what your sensor can handle. I wouldn't recommend using it on scenes where the dynamic range is lower, as this comes off as gimmicky. This is just my personal opinion. If you want to use HDR on everything, Godspeed to you. HDR involves taking multiple exposures and then using software to merge them in your computer to create an image with more dynamic range than a single image. There are other ways, like single RAW HDR and exposure fusions that we will get into later. But first, let's sink our teeth into your normal, run of the mill HDR image.

There are a few things you will need to do HDR.

-Digital Camera with Manual or Aperture Priority modes
-(preferably with Auto Exposure Bracketing [AEB] also)
-Sturdy Tripod (highly recommended, but not absolutely essential. You will see why later)
-Shutter Release (optional)
-Photoshop
-Photomatix Pro
-Imaginomic Noiseware (optional)
-iTunes

Capturing The Images

Once you have these pieces of equipment, we can start taking pictures. Find a scene with very bright highlights and dark shadows. This can be a sunset, sunrise, dark indoor room with bright windows, vehicles, whatever you want. I'd prefer you did not use it on people without then using photoshop to mask them back into the picture with a source image (we will go over this later). Not only do they move too much, but they look ridiculous in HDR. It gives them black speckles all over and weird details that are not at all flattering. Set up your tripod with camera attached in a pretty spot. Or, if your camera can fire upwards of 3 frames a second, you can put it in AEB and just hold it still in hi-speed fire mode. I do this a lot when I need to stay mobile and don't have time to set up a tripod.(or I'm feeling lazy.) Navigate to your menu on your LCD display. Somewhere in there, there will be "AEB". This tells your camera to take 3 or more pictures at different exposures. I usually use 0, +2, and -2 EVs. This works most of the time. For the rest of this tutorial I will assume we are taking 3 photos. Now put your camera in Av mode, so that to change the exposure the camera only has to change shutter speeds. This is so you do not make your DOF shallower or wider between pictures, as it will change the way the image looks obviously. You can also use manual mode and forgo the AEB, just change shutter speeds to give you the images you want. This is what I normally do. Finally, set your ISO to the lowest acceptable level as HDR creates a lot of noise and grain, and you do not want to add to it. Put your camera into high speed shutter mode if you own a remote shutter, or self timer if you do not. This will keep your camera perfectly still between images. Make sure you are in RAW and shoot the pictures until you have 3 taken.

These are the technical instructions on how to take them. Now let me get a little into theory. When you go to shoot an HDR, survey the scene and ask yourself a few questions. Are there moving things in my scene? Are there people in it? How great is the range between light and dark? How fast are the clouds moving? How windy is it? These are all things to consider. Let me say again, I don't like the way people look in HDR, so If there are people, I mask them in from a source file. Moving objects aren't always a problem, but they can be. Fast moving clouds will appear three times in your final image because if you don't shoot fast enough they will move between each exposure. Same goes for branches, trees, and grass on a windy day. I like to do HDR with a wide angle lens so you minimize movement in the details, you will barely be able to see it. Water will obviously look different in your image, No camera can shoot fast enough to freeze waves, especially at sunset with low noise. To combat these problems, I have a rule when I shoot HDR now. For each distinct part of the image, I like to have a separate exposure. So take your 3 images 2 stops apart, and if that doesn't cut it, take some more quickly. Let's say you have a scene with water, fast moving clouds and a piece of driftwood. Take 3 exposures 2 stops apart by metering on the point the foreground meets the horizon (where I always start, This way it averages the bright sky and darker foreground for my first image [0 EV] image.) Then, for your next series, go into manual mode and expose so that the brightest part is kind of dark, then take a shot one stop lower, and repeat until the darkest area of the image is kind of bright. This way you have all the information you need when you go to process. Don't go overboard, you probably won't need 10 exposures.

This one barely needed 3 images

Now that you have the images, go home and grab some tea while your images upload to your computer. (I don't do this, but everyone seems to say this whenever you read a tutorial. I make myself a stiff cocktail, usually) Use whatever Library management tool you use, be it Lightroom, Bridge, Windows Explorer, whatever to select the pictures. I use Bridge. "Mike, why don't you use Lightroom?" Well, I have used it, and found it unnecessary. I have a great system of storing photos on my computer and I do a lot of multimedia things so I need to use Bridge to get it all together. I also make all changes in photoshop and camera raw, so lightroom is redundant. This shouldn't stop you from using it, It's a great program. I also use a PC, so sorry if some of the wording does not apply to macs, I'm trying to be platform neutral here.

Open all the programs you need now. This will save time so that when images are brewing, you can navigate between tabs without waiting too long to load programs.

Now is a good time to talk about the other program I have open, iTunes. I like to keep it chill sometimes when I'm editing, sometimes I like to amp it up. The only constant is you need a soundtrack to work to. I like Hans Zimmer myself while editing, but anything could work. I've run experiments before to see if it made a difference with my images. It didn't, becuase my photographs are always really good

Tone mapping in Photomatix Pro

Highlight your 3 images in your Library program. drag them into photomatix. They can be JPEGs or RAW files. Not much of a difference. If I want to be very technical I will open RAWs first and tweak them, then save as JPEGs and load them.

A dialog box will pop up. Select "merge for processing". Hit OK.

Another dialog box will appear. I make sure these are my files and hit OK. Not much else here.

The next screen is where we start making changes. the first option here is auto-align, I myself do not use it, as my camera was on a tripod, so it should not have moved. If you hand held the camera while taking, check it off. If you do, do not crop the images, you will need your images unadulterated for later steps. I do not like the de-ghosting feature all that much, so I usually leave it off. If something moved I will fix in photoshop. If you do not want to do that in photoshop, check it off and give it a go here, it doesn't do a bad job. It's just not perfect. I reduce noise and chromatic aberrations in photoshop so those are left blank also. Again, if you aren't great in photoshop or just want photomatix to do it, check it off as you will need to reduce noise and if you shot wide open you might need to reduce your aberrations. at the bottom are options to do with the handling of your RAW files. I normally leave the white balance on as shot, my camera does a pretty good job and I can fix it later. Next is the color space. If you going to the web with the image, use sRGB. I use sRGB for everything unless I'm doing a Fine Art Print with it, and even then it would be good enough.

Notice how I'm mostly unchecking everything. Photomatix is great at tonemapping HDR images. It's not that great at reducing chromatic aberrations, reducing noise, etc. I leave these for photoshop. This is why I don't make HDRs in photoshop. Photomatix is better. Each program has it's strengths and weaknesses.

After hitting OK, it will take you to a crazy looking black-ish picture. This file is a 32 bit HDR image. This is a true HDR picture. Your monitor cannot show the full range of information this file holds. This is why we must tonemap the image to make it visible on a mere mortal's monitor. If your monitor can show a true 32 bit file, well you probably don't need to be reading this tutorial. Check it out for a second, then continue by hitting "tone mapping/fusion"

You start with a default tonemap, or whatever you used last time.. Again, tonemapping allows a high dynamic range to be seen on a low dynamic range device, like printer paper or your monitor. At this point the image is not actually HDR anymore, it is a low dynamic range image disguising as an HDR. We call these images "HDR", but they really are not becuase we can see them on our monitor now. Tonemapping gives the illusion of HDR. But alas, we will still use the HDR moniker for now. Play around with some sliders for a few minutes and then continue on to the next step.

Click on the image for a closer look at my settings.These are my "regular" settings in photomatix. I usually start with these settings and then tweak from here. I like a more natural HDR, not super-surrealistic ones. I sell these in galleries and shows, so I assume the client will want a more natural image to hang on their wall. If you are only posting these online or you say "but Mike, your images are terrible, I like my way", then by all means go full strength and knock it out. Here is a list of the most important settings in english:

-Strength: How much contrast enhancement to apply to the image. To the right makes skies darker and the image punchier. To the left, makes it look more natural.
-Color Saturation: Self explanatory. Be careful.
-Luminosity: Basically acts like brightness, to the right you get brighter shadows, to the left it darkens the image.
-Detail Contrast: Adjusts local contrast. Slide to the right for a punchier image. Slide to the left for a bit more natural.
-Light Smoothing/ Lighting adjustments: This one will do a lot to your image. Using the slider, going left makes the image surreal with halos everywhere, while sliding to the right makes it much more natural. Of all the options, be careful with this one. I would not recommend going any farther to the left than a third from the right side if you want even a somewhat natural image. Or, only use Natural or Natural+. You will thank me later.
-It feels like I'm explaining the Electric Slide. Sliiiiide to the left. Sliiiiide to the right....
-Highlight Smoothing: This reduces the contrast in bright areas. Can be used to lighten your sky if it's black (a common side effect of HDR), or to look more natural
-White/Black Point: use these sliders to clip or blow out shadows and highlights, respectively. I like both of mine over 3 for almost every image, makes it look more natural.
-Gamma: Makes the image brighter or darker by adjusting mostly mid tones. A little bit goes a long way, like oregano oil.
-The rest of the advanced options are better off played around with than told examples with, I don't usually mess with them unless I can't get an image right with the rest of the options.

If you don't want to go the HDR route, you can always do Exposure Fusions. These are a bit touchier. Sometimes they turn out great, but most of the time they look pretty dull. I'm not even sure what most of these sliders do, you'll figure it out when you do it. Most of what you can do with fusions can be done in photoshop, so let's do it there.

Go ahead and hit "process" at the bottom of the screen. After the black magic that makes your computer work is done brewing the image, you will have a preview. Look it over, and if it's to your liking head on up and save it. I save in 16 bit TIFFs, so when I put it into photoshop I have 16 bits to work with, opposed to 8 like a JPEG. It's a good thing to always work in 16 bit because it gives you more room to edit in photoshop, you have more data to work with. If I have a killer image I also save the 32 bit HDR file so I can go back and play with it later.

So here we have it folks, we now have our "HDR" image. The fun is just starting. Wait? You thought we were done? Oh no, we have a lot more work to do. These tonemapped images are hardly ever ready straight out of photomatix. They have ugly ghosting issues, black skies, weird seams in the water, and an overall psychedelic look. On the next page we are going to fix this in photoshop.

Finishing in Photoshop

Now that we have captured our photos and processed them in Photomatix, now we will shape it up into a respectable image. Now you should load the tonemapped file and the three source files into photoshop. Once all the files are in photoshop, copy and paste them on top of the tonemapped image. We now need to be able to use masks and layers. I won't be going over layers or masking in this tutorial, it is a whole tutorial in itself. If you do not know how to use layers or masks, I suggest reading up on them here at DPS and skipping ahead a few steps to where we talk about processing the image. Make sure we now have an image with 4 different images as 4 different layers stacked up.

Now we will line up the layers in photoshop so they are perfectly in line. They must be this way so when we mask parts out they line up. Photoshop has an auto align function but I like doing it manually. Just make the layer you are aligning is a "difference" (use the drop down box that says "normal" in the layers window. click on it and there will be a ton of options, just scroll 2/3s of the way down and you will see difference.) layer and you can see when you have them lined up. once every layer is lined up, switch all the layers back to "normal".

Once the layers are aligned, we will start to mask source images into the tonemapped image. Just make a mask on each layer, fill the mask with black (Edit...-Fill...-with black) so you can see the tonemapped image again, then paint with white to add the source image to it in increments. Make sure the layers above the one you are working on have their visibility turned off. I do it in 20% increments usually to start. I'm going to mask the original sky back in if it looks too black. Or, maybe the areas near the horizon got too dark. Maybe I need to mask a person back in because HDR made them look idiotic. By the end of this step on most of my images, the tonemapped image is mostly covered with source images and doesn't resemble the original tonemap, which is a good thing.

Once I'm happy with the image, I make a history snapshot and then flatten the image. Now we just apply normal edits to the image, like color, dodge/burn, noise reduction and sharpening. Noise reduction is very important in HDR because the processing creates a lot of noise and grain. This is another reason I mask source image back into the tonemapped image, sometimes the grain is too much on the HDR and it hurts the image. I use Imagenomic's Noiseware for noise reduction, but you can use normal photoshop noise reduction. I have just very basic edits highlighted here, but they bring the image farther than what you can do in just photomatix.

Now flatten the image, switch back to 8 bit mode, and save it as whatever you want. Now you are done. Wasn't too bad, huh? Remember, HDR is just another tool in your arsenal. It takes a long time to get the hang of it and your first few will be really bad. I'm not kidding. They will be terrible. but after a while, you will get the hang of it.

If you liked this tutorial, make sure you stop by my facebook page Mike Sperlak Photography and "Like" it for more tutorials, news, and sweet images.

If you are interested in seeing some of my HDR photography, here is the HDR page on my website- The HDR Gallery on Mikesperlak.com

Thanks a lot for your time, and I hope I've helped in your quest for knowledge. I wouldn't be where I am today without people putting tutorials on the web for free, and the ones here at DPS are some of the best.

Mike Sperlak

www.mikesperlak.com