Ask Tim Grey

Today’s Question: Still another follow-up question [regarding background color when evaluating photos, covered recently in the Ask Tim Grey eNewsletter]. Is it better to use a neutral gray as background in PowerPoint or ProShow? Do the same principles apply to the view of a slide show? I have always used a black background.

Tim’s Quick Answer: Actually, for a digital slideshow presentation I highly recommend using a black background for the photos, in order to help the photos stand out better.

More Detail: When evaluating a photo for the purpose of applying adjustments to that photo, I recommend using a background that will help ensure you are making the most accurate evaluation possible for the photo. That generally means using a neutral gray background with about a 50% luminance value.

When presenting images as part of a digital slideshow, I recommend using a black background. At least in theory, this translates into no visible illumination of the screen around the photo. In actual fact this generally means just minimal light in those areas. But the point is that this will enable the photo to stand out as much as possible.

Keep in mind that at least in theory, a digital slideshow is being presented in a darkened room. That means the focus of the viewer will only be on the selected photos in the slideshow, and their eyes will adjust in terms of overall exposure based on those images.

Regardless, my preference for projected photos (or those presented on any digital display) is generally to have them surrounded by black, so there is nothing competing with the photos themselves. Of course, in a situation where the images presented in the slideshow need to be critically evaluated, you may prefer to have a middle gray background surrounding the photos. But generally speaking I think it is fair that for a digital slideshow the emphasis is on making the images stand out and look their best, rather than a technically accurate evaluation of the photos.

It is worth noting, by the way, that in some cases the presentation may be about more than the photos. In other words, in some cases you may want a more creative presentation that goes beyond a simple black background. But when your priority is an emphasis on the photos in the slideshow, my feeling is that a black background is best.

Today’s Question: I just can’t get a color from the color swatch in the Graduated Filter to enter the gradient area on the image. With Exposure set at different slider levels to the left, the sky remains dark. I try to put some reasonable blue in and there is no change at all. Any thoughts?

Tim’s Quick Answer: I suspect in this case you are probably either using a color value that is too close to the underlying area of the image, or that your other adjustments (such as Exposure) are overpowering the color effect. I would try moderating the other adjustments, and then select a strong color (such as a very saturated red) to test out the behavior of the Color adjustment.

More Detail: The Color option that is available for the Graduated Filter, the Radial Filter, and the Adjustment Brush in Lightroom’s Develop module (as well as Adobe Camera Raw) enables you to essentially add a color tint into a specific area of a photo. So, for example, you could add a nice blue tint to into an otherwise dreary sky.

To select a color, simply click on the color swatch (the rectangle) to the right of the Color label and choose a color from the popup. That color will then appear in the image based on the current targeted adjustment, depending on which tool you’re currently working with.

If the color you select is very similar to the underlying color in the image, or if the color is very subtle (of low saturation, for example) then the change may not be easy to see within the photo. To get a sense of how this adjustment works, I recommend first selecting a highly saturated color that differs from the color in the area of the image you’re applying the adjustment to.

Once you’ve refined the definition of the area you want to affect within the image, you can modify the other adjustments you want to apply, and fine-tune the color selection for the Color adjustment. Along the way, you may notice that applying strong adjustments (such as with Exposure) may mask the color so that it can’t be seen very easily.

Of course, in many cases you may want a relatively subtle color for the Color adjustment, so that the result blends in to the surrounding image in a pleasing way. But by starting with an exaggerated color and refining from there, you’ll get a better sense of what is possible with this adjustment.

Today’s Question: When applying a graduated filter effect in Adobe Camera Raw [or Lightroom], is it possible to adjust how hard or soft a transition you want, just as you can choose in actual graduated filters between hard and soft graduated transitions?

Tim’s Quick Answer: Yes! The softness (or hardness) of the transition for a Graduated Filter adjustment is determined by the distance of the gradient you define. You can set the size when you initially drag on the image to create the gradient, or adjust the size of the gradient after it is defined to fine-tune.

More Detail: When applying a targeted adjustment in Adobe Camera Raw or Lightroom using the Graduated filter, there are two ingredients involved. The first is the gradient itself, which determines where the adjustment is visible. The second is the set of adjustments you apply for the Graduated Filter adjustment.

As noted in today’s question, the graduated neutral density filters that can be placed in front of the lens to “hold back” a bright sky and even out the overall exposure for the scene are available with transitions of various sizes. In effect, you can find graduated filters with a short versus a relatively long transition for the gradient on the filter itself.

Similarly, you can adjust the distance covered by the gradient for the Graduated Filter adjustment to control the size of the transition between the area of the photo receiving the full adjustment and the area of the image receiving no adjustment.

When you initially create a Graduated Filter adjustment, you can drag across the image to define the gradient. So, for example, you can drag from an area of the sky near the horizon down to an area just below the horizon to create an adjustment that will affect the sky and then transition smoothly to no adjustment for the foreground.

The distance you drag initially determines the size of the transition for the gradient. But you can also adjust the size after creating a gradient with the Graduated Filter. The two outer lines represent the distance of the gradient transition, while the middle line determines the angle of the gradient. So you can drag the outer lines in or out (closer to or farther from) the middle line to adjust the size of the gradient.

And, of course, you can then refine the adjustment controls to achieve the desired effect for your graduated adjustment. In other words, you can go back and forth between modifying the overall “shape” of the gradient and refining the adjustments to be applied, until you’ve achieved the desired result for the image.

Today’s Question: To piggyback on a question from last week: I edit in Lightroom with the light gray background. Based on what you said today, should my editing background be white?

Tim’s Quick Answer: I do not recommend using a white background when editing your photos on the computer. Instead I recommend a middle-tone gray value.

More Detail: Using a white (or other neutral) border for a print can help ensure that the viewer’s vision will automatically compensate for the color of the light illuminating the print, and therefore perceive more accurate colors in the print.

While the same concept can be helpful in the context of color for an image being evaluated on a monitor display, it is important to also consider the impact on your perception of tonality.

If you use a bright white background for your photos while evaluating adjustments, you’ll tend to perceive that image as being darker than it really is, and you may apply adjustments that result in an image that is too bright. Conversely, if you use black as a border around your image while evaluating that image on the monitor display, you may adjust to make the image appear too dark.

In addition, a dark border will tend to cause you to perceive greater saturation in the image. As a result of all of these issues, I recommend using a background for the photo that is neutral (a shade of gray) and that is around a 50% brightness level.

In the context of Lightroom, you don’t actually have a significant amount of control over the tonal values present in the interface. You can adjust the Fill Color option on the Interface tab of the Preferences dialog, but this only controls the space around the image itself, not the overall Lightroom interface. I prefer the “Medium Gray” option for this setting, which is the default.

My second choice would be to use a black background, since at least in theory with a monitor display that means there won’t be any light emitted around the photo. There are some potential drawbacks to evaluating a photo in this way as noted above, but in general this won’t have a huge impact when evaluating an image. For example, I’ll sometimes switch to the full screen display of an image in Lightroom by pressing “F” on the keyboard to toggle into or out of that view. This provides a convenient way of viewing only the image itself (albeit against a black background) for purposes of evaluating the adjustments you’ve applied to the photo.

Today’s Question: Where do you buy 5000 Kelvin light bulbs? I get most of my prints made at Costco and their ambient light is suspect at best. I have to take the print out into the daylight outdoors to see what the print will really look like. And then my print will look different in my client’s residence depending on their ambient light situation. How do you deal with this?

Tim’s Quick Answer: There are a wide variety of options for 5000 Kelvin light sources, including replacement bulbs for standard fixtures (http://amzn.to/2h82WIP). There are also custom lamps and viewing booths you could consider. But ultimately the light used to illuminate a print can impact the experience of viewing that print.

More Detail: In an Ask Tim Grey eNewsletter last week I made reference to the fact that a 5000 Kelvin color temperature illuminant was the basis of a color-managed workflow. In other words, color management standards define a 5000 Kelvin light source as the color temperature that should be used for evaluating a print.

Evaluating a print is one thing, of course, but actually exhibiting the print can be something altogether different. In many gallery displays, for example, relatively warm halogen lighting is used to illuminate prints. In other cases you may have relatively cool (slightly blue) LED lighting, or even fluorescent tubes with a variety of possible color values.

In other words, a perfect color-managed workflow in your studio doesn’t always mean a print will be presented in a way that enables a truly accurate view of the colors in that print. The white point adaptation feature of human vision can help compensate for this issue, but it is certainly preferred to have consistent lighting for a print whenever possible.

As noted above, you can find a sample of a replacement bulb for a standard light fixture that provides a 5000 Kelvin color temperature by following this link:

http://amzn.to/2h82WIP

In addition, there are dedicated print viewing booths, which provide a full environment for viewing the print under a 5000 Kelvin light source. You can find a sample of such a viewing booth by following this link:

http://timgrey.me/pdv1ebh

To me the key is to make sure that your print looks perfect under standard viewing conditions. If you include a white matte around the photo you will help ensure that the white point adaptation of human vision will help compensate for the lighting in a variety of different environments. Otherwise, the only other solution would be to produce a print that is fine-tuned for the specific lighting under which it will be displayed. But that can obviously be a challenging proposition!

Today’s Question: Could you please explain how and when to use the Guided Upright control in the Transform section of the Develop Module found in the recent Lightroom upgrade?

Tim’s Quick Answer: Once you’ve selected the “Guided” option in the Transform section of the right panel in Lightroom’s Develop module (or via the Transform tool in Adobe Camera Raw), you can click-and-drag within the image to draw from two to four lines within the image to define lines that should be perfectly horizontal or perfectly vertical. The image will then be transformed to straighten those lines to the extent possible.

More Detail: There are a few things that can help you achieve a better result more easily when using the Guided Upright adjustment.

First, I highly recommend making use of the “Show Loupe” option (which is enabled by default) so you can see a zoomed-in view in a small box adjacent to your mouse pointer. This loupe can be very helpful in making sure you are aligning the lines you draw for Guided Upright precisely along the actual lines you want to straighten in the image.

I also recommend making the lines you draw within the image as long as possible based on the references available within the photo. If you draw very short lines, a tiny mouse movement can translate into a significant change in angle for the line. With a long line, small movements will have a relatively small impact on the angle of the line, helping to improve your accuracy.

When distortion is a significant issue, such as for photos captured with a very wide-angle lens, I also recommend keeping the lines you draw as close to the outer edge of the photo as possible, since that is where the distortion is likely to be greatest.

In theory it is possible to only draw two lines with the Guided Upright control. Those could be two parallel lines to adjust only the horizontal lines or only the vertical lines within the image. You could also draw one horizontal line and one vertical line to correct in both directions. However, whenever possible I recommend drawing two horizontal lines and two vertical lines to provide the Guided Upright adjustment with as much data to work with as possible.

You’ll notice that when you draw your first line in the image after selecting the “Guided” option, there is no change in the image. You need to draw at least two lines for the Guided Upright adjustment to apply. The maximum number of lines is four. I think you’ll find that if you pay careful attention to the lines you use as a reference in the photo, you’ll be able to achieve an excellent correction very quickly and easily using Guided Upright.

Note that the Guided Upright adjustment is only available in the Creative Cloud version of Lightroom, not the standalone version. Frankly, this feature alone may be reason enough to consider a subscription to the Creative Cloud Photography Plan.

Today’s Question: How do you determine a color cast visually on prints? In one application for membership I was told 4 of my images had color cast in the prints.

Tim’s Quick Answer: It can be surprisingly difficulty to accurately evaluate whether there is a color cast in a print. Your best bet is to use a light source with a 5000 Kelvin rating to illuminate the print, and to surround the print by a pure white background.

More Detail: The human visual system includes a feature referred to as “white point adaptation”. What this basically means is that our visual system attempts to eliminate the effect of a color cast caused by the light illuminating a scene. So, for example, if you see a white object illuminated by a yellow light source, you “know” the object is white even though it actually appears with shades of yellow.

This white point adaptation can effectively cancel out the color of the light source, but it can also cause you to automatically correct for other color problems in a scene, such as when viewing a printed image.

To help compensate, you want to ensure that the print is viewed with a clear reference for what actual white looks like. A 5000 Kelvin light source is the basis of print evaluation with most color management standards, and therefore is the illumination source that should generally be used to evaluate prints.

In addition to a bright and neutral light source to illuminate the print, a pure white background surrounding the print will provide your visual system with a clue as to what white looks like, and thus you’ll be better able to detect a color imbalance in the print.

Of course, even at this point it is not always easy to see the actual color cast in a print. We all have different color vision abilities, both in terms of the accuracy of our vision as well as our ability to differentiate small differences in color. I have found that with practice it becomes easier to detect a color cast in the prints, but it can still be a bit of a challenge to be able to see such a color cast clearly.

I recommend practicing the process of critically evaluating prints under the viewing conditions described above, and you’ll likely find that it becomes easier to detect a problematic color cast in a print.

Today’s Question: When it comes to the XMP files you recommend creating to save metadata with RAW captures, does the RAW file still work usefully without it? What damage is done when the XMP gets disconnected from the RAW file?

Tim’s Quick Answer: When an XMP “sidecar” file is created for a RAW capture, it contains metadata that was created after the RAW capture was created, and therefore not included in the actual RAW capture file. Thus, losing the XMP file will take you back to the original RAW capture as it came from the camera, missing only the metadata you updated after the capture.

More Detail: One of the primary purposes of an XMP sidecar file is to enable you to update metadata for a RAW capture without actually altering the RAW capture file. In other words, the RAW capture can be treated as an original that should not be altered, with all updates being performed in a non-destructive way.

In the case of Adobe Camera Raw and Lightroom, for example, most metadata updates along with the adjustment settings you’ve applied to the RAW capture can be stored in an XMP file alongside the RAW capture. The XMP file will have the same base filename as the RAW capture that it relates to.

In Lightroom your metadata updates and Develop settings are not written to an XMP sidecar file by default. Rather, those updates are only saved within the Lightroom catalog. However, you can enable an option in the Catalog Settings dialog to also automatically write updates to an XMP sidecar file for your RAW captures.

The whole point of an XMP file is to leave the original RAW capture untouched. Thus, if you lost the XMP file for any reason without losing the RAW file, that RAW file would still be intact and could be processed without difficulty. You would lose metadata updates from the XMP file, although if you are using Lightroom that would not be an issue because the updates would still be stored within the Lightroom catalog. But ultimately the most important file is the original RAW capture, and it is certainly possible to continue working with that RAW file even if the associated XMP file were lost.

Today’s Question: What does it mean for a color to be out of gamut, and how does it happen?

Tim’s Quick Answer: A color that is “out of gamut” is beyond the range for the current definition of available colors. One of the most common scenarios where we refer to colors being “out of gamut” relates to a situation where the printer, ink, and paper combination you’re using to print a photo can’t reproduce some of the colors defined within the actual image file for that photo.

More Detail: Ultimately, an out of gamut color is one that can’t be reproduced in a given context. In other words, when someone says that a color is out of gamut, it is always understood that it is out of gamut for a particular purpose. The color exists within our source image, for example, but can’t be reproduced with a particular type of output (such as printing).

When you’re applying adjustments to a photo, there are no colors that are out of gamut in that context. In other words, if you apply an adjustment it can only result in color and tonal values that are actually available. There is an underlying color space in use whenever applying adjustments, and that determines which colors are actually available for the image you’re working on.

If you think about tonal values I think it might be a little easier to understand the concept at work here. In a photo you are optimizing on the computer, the darkest value you can produce is black, and the brightest value is white. If you apply an extreme darkening adjustment to the photo, a large number of pixels may become black, but none of them can become darker than black. There are limits to the range of values available for a photo, you can’t produce values outside of that range.

If you print that photo, however, the darkest black that a specific printer, ink, and paper combination can produce might not be especially dark. And if the paper isn’t pure white, then the brightest value available for the print won’t be especially bright. In other words, the black in your source photo is too dark to print, and the white in your photo is too white to be represented accurately by the paper. That is essentially what “out of gamut” refers to.

While you can apply adjustments to your photos to produce any color or tonal value that is available based on the working color space in use by that software, that doesn’t mean you’ll be able to reproduce all of those tonal and color values with every possible method for producing output based on that photo.

In theory you could keep your adjustments modest so that, for example, you don’t end up with colors that are too saturated to be printed accurately. In practice you will generally want to optimize your photos so they are perfect from your perspective. Then you can determine if there are limits to how that photo can be printed through the use of soft proofing or print testing. That, in turn, may cause you to choose a specific print configuration, such as using glossy paper rather than matte paper in order to be able to produce a print with greater saturation.

In other words, colors are only out of gamut in the context of specific output, and since we tend to share our photos in a wide variety of ways that generally means we need to consider these gamut issues when producing output. When optimizing the photo on the computer, the focus is generally to produce a truly optimal source file, leaving issues of output to a slightly later stage of your workflow.

Today’s Question: When I bring an image into Adobe Camera Raw, the RAW file’s histogram shows overall clipping on the left side. If the camera is not showing clipping, how can one prevent clipping in the RAW file?

Tim’s Quick Answer: The histogram you see in Adobe Camera Raw (or any software for processing RAW captures) is based on the adjustment settings for the RAW capture. In other words, if there was no clipping shown on the camera there shouldn’t be any clipping in the RAW capture data, and so you’ll be able to recover the detail that appears to be clipped by refining the adjustment settings.

More Detail: When working with a RAW capture it is a little to see an accurate histogram, because the actual histogram really depends on how the source data is processed. Keep in mind that a RAW capture represents the actual information gathered by the image sensor during an exposure. That information then needs to be processed in various ways.

For example, I think many photographers are aware that most digital cameras only capture a single color channel for each individual pixel on the image sensor. Software then needs to calculate the “other” values for each pixel to produce full color information.

The bottom line is that there is a degree of interpretation involved when processing a RAW capture. As such, the histogram may vary based on how the information is interpreted, and what adjustments are applied along with that interpretation.

The image you see on your camera’s LCD display for a RAW capture is essentially representing an in-camera RAW conversion. That means the histogram you see on the camera is based on the in-camera RAW conversion, while the histogram you see in Adobe Camera Raw (or other RAW-processing software) is based on the interpretation of that specific software.

To add to this confusion, changing the color space option on your digital camera will generally cause the histogram to change based on that color space. So even your camera might be capable of presenting different interpretations of a histogram for a given RAW capture.

Certainly it can be a little unnerving to see different histograms for RAW captures depending on how you’re viewing the image. But rest assured that if the camera shows there is no clipping you can feel confident that the information within the RAW capture represents no clipping of data for the photo. Thus, if you see clipping in software such as Adobe Camera Raw, it simply means you need to refine the adjustment settings to refine the interpretation of the RAW data.
So, for example, simply reducing the value for Whites and increasing the value for Blacks in Adobe Camera Raw will “recover” the information that appeared to be lost on the histogram display, based on the default interpretation of the RAW capture.