Down to Brass Tacks Let's cut the crap.

Mixing Flash with Ambient

Setting the shutter speed in the light meter

When using a Sekonic L-358 light meter to read a flash exposure (the same applies to other models, I am simply not familiar with them), one of the nice features it has is its ability to indicate which percentage of the total exposure came from the flash — the rest of the exposure being from the ambient light available in the location where the metering was done.

Here is a figure taken from the L-358's user manual:

As you can see in this example, 70% — "Percentage of flash in total exposure" — means that the flash was responsible for 70% of the total light, while 30% came from the ambient light available. The total amount of light ended up requiring an aperture of f/5.6 and 3/10th (let's call this f/6.3).

If 30% of the total light gathered by the light meter during a reading comes from the ambient light, if you change the shutter speed (without changing the flash power), you should expect that percentage to change: the longer you expose, the more the ambient light will have an impact on the total light, since you will gather more of it (while still gathering the same amount of flash). On the other hand, if you expose for a very brief moment, you will gather very little of the ambient light (while still gathering the same amount of flash), so the ambient light won't have much of an impact in the total light.

You might very well end up in a situation where the flash is only responsible for a small fraction of the total light (say, 10%) or, at the other extreme, end up in a situation where the ambient light has no influence on the exposure (which would give a 100% flash exposure). For example, when working in a studio environment, we usually don't mind leaving the modeling lights on when shooting, because we know that the light they produce is insignificant in the total exposure compared to the flash power (we get a 100% flash exposure all the time regardless).

Now, coming back to a location shoot where we mix some ambient light with flash, we should often expect situations where the percentage of the flash in the total exposure will not be 100%. In the situation of the figure above, where 70% of the total light came from the flash, suppose we were to expose for 1/30 instead of 1/125 — that is two stops more ambient, giving us a brighter background. In this case, the flash would now only account for ~40% of the total exposure. What's more, since we're adding ambient light to the previous exposure (flash remained the same), we now have more light overall, so we must use a smaller aperture — we go from f/6.3 to ~f/9.

This makes the shutter speed a crucial parameter to provide to the light meter, otherwise the obtained value will be wrong.

The only situation in which we could ignore the shutter speed would be in a pitch-black room where the only light is the flash — in this case, the ambient light (or lack thereof) would have no impact in the reading whatsoever.

Changing our perception of flash color gels

If you're mixing flash with ambient light, you know that you can (must?) correct the color of the flash so that its light color is well harmonized with the ambient light color, lest you get a quirky result.

But you can also use color gels not necessarily because you want to make the two light sources the same, but because you want to add an effect, such as warming up the subject so that it contrasts more with a colder background, for example.

In the image below, both the foreground and the background lights are of the same neutral color:

Using a CTO gel (orange) on the flash aimed at the subject, you can warm up the subject, which will further isolate it from the background (which will now be of a relatively colder color than subject, even if it is the same as in the first shot):

Indeed, while the background remained the same, it can be said that the subject is warmer.

You will notice that I also (conveniently) included a gray card in the frame. If we take the picture above (the same exact file), but that we color correct using the gray card, here's what we get:

You will notice that the subject is now perfectly neutral — exactly back to what we had in the first frame — but that the background turned blue (colder)! In this case, can it be said that the subject is warmer than in the first shot? Absolutely not — in fact, they are exactly the same, after correction, even if a "warming" gel was used.

If you're going to include a gray card (or GretagMacbeth chart) in your frame, you might want to do it while you're not using a gel on the subject, otherwise, balancing the color with a neutral reference will remove any color you might have thrown on the subject and, rather, affect the background. If you're going to include a gray card in your frame while you are using a gel, the way you should look at it is that you are in fact changing the color of the background in the opposite direction than that of the color gel (e.g.: if you're using a warming color on the subject, you're actually not changing the subject, but rendering the background colder!)

The fact that we are using a "warming" gel has no bearing on the final look of the image, because it depends on the white balance selected. A "warming" gel might therefore be more meaningfully seen as a "gel that makes the background colder"! That is why, when you work indoors under tungsten lights, you use a warming gel: not to warm up the subject (you still want it neutral), but rather to make the background colder.

On White Balance

So you want to get accurate white balance. There are many ways to get there, if you know why you are doing it and what you want to achieve.

If you're shooting raw, you're probably aware that you don't technically need to worry about it at capture time, because it's not set in stone — whatever setting you use won't definitely affect your final image; you'll easily be able to change it in your raw processor. (Of course if you're shooting JPEG, then you'll definitely want to nail it as close as possible to your objective to minimize the amount of manipulation required. But you're not shooting JPEG anyway, are you?)

So you're shooting raw. Why even bother performing your white balance at capture time, then?

• One reason might be to get a better approximate histogram, so that you can better judge your exposure. Indeed, you might think that one of the channels is clipping when, in fact, it's the color cast that was throwing off the histogram. But then again, if you're evaluating the exposure another way (say, with a light meter), then this won't matter to you.
• Another reason might be to get a better approximate image preview, so that you can better judge the colors. Of course, you can't really rely on the image preview on that little LCD for accurate color evaluation, but surely, if the color balance is completely off, it might be quite misleading. But then again, you might only use the image on the LCD to judge the composition, pose and other aspects of the image, keeping in mind that color will be dealt with afterwards, so this, too, might not matter to you.
• Yet another reason might be so that when the unprocessed images pop up on your computer screen, the client watching you work will have a better idea of what the images will look like right away. Indeed, the client might not respond well if there is an annoying color cast in the images, even if you know you'll fix it later. But if you're not shooting tethered with a client watching over your shoulder, this might not matter to you either. (Note that some raw processors, such as Capture One, can be configured to automatically apply a certain white balance to all imported images, so that the images are immediately corrected, regardless of how they were shot, which is another reason why performing in-camera white balance might be irrelevant to you.)

Only you can know how important it is for images to be properly balanced at capture time, but if you want to do it, there are many ways to go about it.

• One way is to use the Auto White Balance feature of your camera. Sometimes, in rapidly/wildly changing light situations, this setting might be more efficient at getting a decent approximate white balance than having to fiddle repeatedly with your camera's parameters. If you're not working in such a difficult situation and the color of the light is not changing — say, you're working in a studio — then this setting might, on the contrary, produce unpredictable results.
• To get consistent results, another way is to use one of the white balance presets your camera offers — things like "sunny", "cloudy", "tungsten", "fluorescent", etc. This usually won't give you an exact result, but you'll likely get reasonably close to your target for your histogram and image preview to be very usable.
• If this is not good enough, a more sophisticated way to set the white balance would be to manually enter a kelvin temperature (which, unfortunately, only affects the blue-yellow axis, not the green-magenta color), or further tweak the result with the "white balance shift" tool. (Have fun. Who wants to spend time doing that?)
• Finally, the most accurate in-camera result you can achieve would be to use the "Custom White Balance" feature.

Bear in mind that whatever approach you choose, none — not even the custom one — will give you a surgically exact result. The only way to get a better result would be to include a neutral reference in a photo under each light situation, and later use that reference to synchronize the white balance for all the images shot under this type of lighting.

For the most accurate readings, you might include a tool like a WhiBal gray card, which is good to take care of the white balance, or go one step further with an X-Rite ColorChecker Passport, which includes a good ol' Gretag MacBeth color chart as well as the software required to generate camera calibration profiles for Lightroom — serious business!

If you don't want to spend the money (or carry these around, or shoot those test shots), for fairly good results, many common objects will be good enough to get you close to your target and allow you to work without having to worry too much about color. This might be a piece of white paper, tissue, gray hair, etc. It would be pretty hard to judge if these references are absolutely neutral (unlikely), so you understand that those are not perfect solutions. (For example, stuff usually increasingly turns yellow as it gets older.)

But keep in mind that few situations require critically accurate color — you be the judge. (Sometimes, even a perfect white balance won't be enough and colors will have to be manually tweaked in Photoshop with a virtual reference anyway (such as a Pantone swatch), and yet even then, color accuracy will likely take another hit when the image gets to the printer, so this discussion is at least partly moot.)

Now, in those situations where extreme color accuracy will not be an issue, you will have to determine if accurately reproducing the scene is what's important to you. Often, perfect color balance will not yield the image that will look better to your eye — you might very well decide that warming, cooling or otherwise coloring your image will produce something that is more pleasing, whatever light was there the moment you took the picture. You might even decide to convert your images to monochrome, and maybe even to tone them. Yet another reason why you might not need to worry too much about technical accuracy, but more about achieving an image that speaks to you.

For those reasons, on a more practical/pragmatic note, unless critical color accuracy is expected, I will usually save time and use one of the camera presets to get reasonably close results in-camera (so that I can still get useful information out of my histogram and image preview), include a WhiBal in the first shot if there are no other useful neutral references around, and tweak the results in post anyway. If I know in advance that I will deliberately change the look of an image, I might use a different preset (such as using a "cloudy" setting on a sunny day to make the image warmer); this will give me a better instant feedback, even if it won't have any definitive effect on the image until I make the final decision/adjustment in post.

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If you still want to perform a custom white balance to get as close as you can in-camera, note that Canon and Nikon employ dramatically different procedures to achieve this (I am not familiar with the way other brands work):

• With a Canon camera, the procedure requires a ridiculous number of steps (which explains why I usually don't bother). You first have to shoot a picture of a neutral reference, filling the center part of the frame with it. You then have to go to the "Custom WB" menu option. You then have to point the camera to the picture of the neutral reference you want to use for the calibration (usually the one you just shot), and then confirm your choice. You then have, each time, to dismiss a non-removable reminder that tells you to change your white balance setting to "Custom". You then have to go ahead and change the white balance setting to "Custom". (Still there?) If this wasn't enough, you'll also be left with an otherwise useless frame, on your memory card, that was shot just for this, which you might want to delete. (Or you'll keep it and use it to perfect the correction in post...)
• With a Nikon camera, the procedure is decisively more efficient (take a hint, Canon). Set the camera to the "Pre" (preset) white balance setting. Hold the white balance button for two seconds until "PRE" starts blinking. Shoot your neutral reference.

If the procedure fails because the camera doesn't want to take the shot, this is because you're in a "one-shot/AF-A" autofocus mode that won't allow you to shoot until focus is obtained. Contrary to what you might have been told, performing a custom white balance does not require the camera to be set to manual focus, but since the neutral reference is usually a plain card, the AF system simply won't be able to achieve focus, which is the reason it will appear not to work. Just focus on something else or set the lens to manual focus — it doesn't really matter, as long as the center part of the frame contains the neutral reference. (If you're shooting in a continuous AF mode, this won't be an issue.)

If the procedure fails with the camera telling you it couldn't perform the calibration, that's because the exposure was completely off: the camera cannot read the color information out of a clipped highlight. Make the exposure average, or use a semi-automatic mode just for that shot (such as aperture-priority).

Make sure you actually do your reading based on the actual light conditions you'll be shooting in... This is especially relevant when you're working with flash — you don't want to perform your studio calibration based on the ambient light, or your location calibration on incorrectly gelled/randomly bounced mixed-light and get results that don't make sense.

Camera Raw Workflow Options

You know that "link" at the bottom of Camera Raw?

It allows you to change a couple of important Camera Raw options. These settings are not image-specific, meaning that they are not saved in the metadata of a file (be it in the XMP or embedded in a DNG) and therefore cannot be synchronized between images. These settings are global and if you never change them, they will never change from image to image.

With that said, let's look at these options in more detail:

First of all, we have to understand that a raw file is not yet processed, it is not yet a matrix of "pixels", therefore it doesn't yet have a color depth or color space — it is only the end result of the processing that is made to fit inside those constraints.

In order for Camera Raw to present to you a preview of the file as it will look like once processed and to present to you an histogram that is representative of that preview, it has to know to which color space and bit depth you will export the file. (If you've been working with Adobe Lightroom, you know that there is no such option window — that is because Lightroom works natively in ProPhoto RGB at 16 bits/channel and only (optionally) converts to more restrictive constraints when images are exported or sent to an external editor.)

In Camera Raw, you will notice right away that if you choose a smaller color space in the workflow options (say, sRGB), the image preview and histogram will automatically reflect that change: highlights and shadows will be clipped far sooner, as a result of values being constrained to a narrower gamut. Therefore, you should set these options before you start processing your raw file, otherwise you will be mistaken in setting your white point, saturation and other significant values.

Speaking of color spaces...

Different people have different opinions on the matter of color space, but I prefer to work just like Lightroom, in ProPhoto RGB at 16 bits/channel, and only squish image data at the very end of the workflow (usually when exporting images for the web). If you've been reading reviews of the latest inkjet printers, you will know that Adobe RGB is not big enough any longer. Here is an excerpt from a review of the Epson Stylus Pro 7900/9900 printers:

This new ink set is called Ultrachrome HDR and for the first time in an Epson Pro series printer Green and Orange inks are utilized. This actually allows these printers to exceed Adobe RGB in certain parts of the spectrum, by a not inconsiderable margin.

What this tells us is that we don't know what new technology will pop up around the next corner, therefore we should keep as much information in our original files as possible — it doesn't hurt since we're keeping the files in 16 bits/channel.

Speaking of bit depth...

Indeed, there is no question that you should work in 16 bits/channel. 8 bits/channel is generally okay for a final image, but not for one that is still subject to manipulation (since, as we know, manipulation implies loss of information). If you start with 8 bits/channel and manipulate, you will end up with less than 8 bits/channel, and this will likely show up as posterization (especially in smooth gradients) — you know you're in this situation when your histogram has gaps.

That being said, Color Space and Bit Depth are really the only two workflow options you should consider while working in Camera Raw, as they are the only ones that will have an immediate effect — all the others will only have meaning once you export the image out of Camera Raw.

The only time you would play with the other settings (Size, Resolution and Sharpening) is if you were going to use Camera Raw itself to export finished products. I personally prefer to let Photoshop handle that, so I actually never touch these settings (except the first time I open up Camera Raw after installing the Adobe Suite, of course), leaving them as they appear in the screenshot above, for optimal quality.

The problem is that if you change these settings, the next time you open up Camera Raw, you will have to reset them back to the original values — something you are likely to forget, which would mess up your files (more on that later). This constant hassle to reset the settings back and forth depending on the usage of the file (immediate export vs. further work in Photoshop) is enough to make me want to batch process my exports through Photoshop and always leave these options alone to the optimal quality.

To complete our exploration of the options...

As I was saying, unless you're going to, say, export JPEGs for the web directly from Camera Raw, you should leave the Size option to the 1:1 value (no upresing nor downresing). Resizing is better left to the specialists — the algorithm applied here is not as optimal, nor as parametrable as the one you can use in Photoshop. Every resizing calls for interpolation, which means loss of detail, so you should only go through one resizing procedure, if needed, at the very end of the workflow, before you export.

Resolution, as it's been said before, doesn't mean anything until you start talking about printing. Whatever value you put here is meaningless as long as the file is not actualized. Stick to 72 if the file is going on the web (merely because that is the established standard), but otherwise, this number has no effect on the image whatsoever.

Output Sharpening, too, should definitely only be used if you're going to export files directly from Camera Raw. This, too, is a step that should be done at the very end, and is specific to where the file will be going. You don't apply the same sharpening on files viewed on screen vs. files printed on glossy paper vs. files printed on matte paper vs. etc., so you shouldn't apply it at this point if the file will be going to Photoshop for further processing.

To wrap up

Frankly, unless you're going to use Camera Raw to export images directly, to get optimal results, save time and avoid mistakes, I strongly recommend you use the settings shown in the screenshot above and never bother touching them again.

But it gets better...

Wouldn't it be nice if you could just change your mind later, once you're in Photoshop and it's too late because you've left Camera Raw? Wouldn't it be great if every setting in Camera Raw could still be changed later, once you're in Photoshop (and I really mean every setting, not just the workflow options)?

Well, they can, and it's amazingly simple to do! Instead of using the "Open Image" button (which rasterizes the raw file for good), simply hold the "shift" key to turn the button in an "Open Object" button. Ta-dah! You're now working with a "Smart Object": the raw file is now embedded inside your Photoshop layer and can always be edited back in Camera Raw when needed.

To bring the raw file back in Camera Raw, simply double-click on its thumbnail, and voila!

Note that this embedded raw file is not linked in any way to the original raw file that was opened as a Smart Object — you could always move the initial raw file or delete it altogether and it would not affect your image in Photoshop. Note as well that any Camera Raw parameters you change when editing your Smart Object will not be applied to the original raw file neither. It really is a copy of the raw file that was embedded inside the Smart Object, not just a link that was established.