Ask Tim Grey

Today’s Question: I created a layer mask [in Photoshop] to separate my subject from the background so that I could apply more image noise reduction to the background than what the subject will get. I am also using the same mask to blur the background but not the subject. If I combine the two layer masks into a single selection, the entire image is not selected. How can that be?

Tim’s Quick Answer: The short answer here is that adding two selections together doesn’t produce a result where the luminance values in the shades of gray of a selection are exactly added together. In effect, adding luminance values of 50% plus 50% does not yield 100%, but rather 75%.

More Detail: In most cases this behavior is not a real problem, because the specific impact of a particular shade of gray on a layer mask isn’t critical. The result achieved with white on a layer mask (the full effect is applied) is important. And the result achieved with black on a layer mask (none of the effect is applied) is important. Shades of gray in between tend to be less important.

Still, this behavior can be problematic when combining different layer masks or selections together. For example, let’s assume a simple selection that is 50% selected. If you invert the selection that area would still be 50% selected. But if you merge the two selections together, you don’t end up with 100%.

In other words, merging two selections together, where the second selection represents the inverse (the exact opposite) of the first selection will not produce a result where all pixels in the image are selected.

I’m sure there is some complicated mathematical explanation for why this situation makes sense, rather than what we might consider a more “logical” approach to combining selections and layer masks. But the bottom line is that if you want to select the entire image, you should use the “Select All” command found on the Edit menu, rather than combining existing selections or layer masks.

Today’s Question: In a recent episode of Tim Grey TV you made reference to the GPS receiver in your camera. What happens in a situation where you don’t have a reliable GPS signal? Do you get inaccurate location information?

Tim’s Quick Answer: When there is not a reliable GPS signal, the GPS coordinates embedded in metadata may be inaccurate, or they may be missing altogether. Therefore, it is important to keep in mind that even when location information is embedded in your photos automatically by your camera, the information may not be especially accurate.

More Detail: The implantation of the GPS feature varies among the different cameras that include a GPS receiver. My primary camera (in part because it includes a built-in GPS receiver) is the Canon EOS 7D Mk II (http://timgrey.me/tgtv7d2). This camera (similar to other cameras) will present an indication that the GPS feature is enabled, and that a signal has been acquired.

A variety of factors can impact the accuracy of a GPS signal, so even when you have a “good” signal the resulting coordinates may not be completely accurate. The relative accuracy of a GPS signal is often expressed as a distance. For example, a good signal might represent accuracy within 3 meters, while a not-so-good signal might represent accuracy within dozens of meters or more.

During my current travels I actually experienced several situations where a reliable GPS signal could not be achieved. This happens indoors, of course, but while photographing along the inside passage in Alaska there were a couple of situations where no GPS coordinates were recorded by my camera. For example, when in the Russell Fjord photographing Hubbard Glacier, the surrounding landscape was high enough to interfere with acquiring an adequate GPS signal, and so no coordinates were embedded in the metadata for my photos.

In other situations I have observed GPS coordinates that were not very accurate. In some cases the coordinates may have shown that the photo was captured down the street from the actual location, and in other situations I’ve seen coordinates that were off by more distance, perhaps around half a mile or so. Various factors can impact the relative accuracy of the GPS signal, and different cameras will handle the situation differently. But again, there are circumstances where no GPS coordinates will be embedded in your photos even when that feature is enabled, as well as circumstances where the coordinates that are embedded are less accurate than you would normally expect.

In situations where it is important that you know the location where photographs were captured with some precision, I do recommend reviewing the location information for your photos. You can do this, for example, in the Map module in Lightroom, even moving photos on the map to update GPS coordinates as needed based on the map.

Today’s Question: I appreciate that you include the camera settings with your photos when you share them, as I find that information informative. However, I’m confused about the settings for one of the images you shared on 500px:

https://500px.com/photo/151520179/mountains-at-hubbard-glacier-by-tim-grey

Your metadata shows that the shutter speed was 1/8,000th of a second. Why would you use such a fast shutter speed for a subject that wasn’t moving?

Tim’s Quick Answer: This was essentially a case of “insurance speed”. I was on a moving ship (though moving slowly), was using a long telephoto lens (600mm focal length for the photo in question), and I was shooting hand-held. Thus, I wanted the fastest shutter speed I could reasonably achieve to help ensure a sharp photo under the circumstances.

More Detail: The photo shown on my 500px page at the link above was captured near Hubbard Glacier in Alaska. We had started to depart the Russell Fjord when I spotted the snow-covered peaks. The ship had already been moving, and I was using a Tamron 150-600mm lens (http://timgrey.me/1WyqJ4n), frequently zooming all the way to 600mm.

I was not using a tripod at this point, in large part because the ship was already moving. The vibration of the engines can be transmitted through the ship itself, through the tripod, to the camera, causing blurring. In addition, maneuvering on the deck of the ship can be a challenge with a tripod. Although the sky was overcast, the layer of clouds was relatively thin and so I was able to achieve fast shutter speeds. So I opted to work without a tripod.

When shooting hand-held, the general rule of thumb is that you want the reciprocal of your shutter speed to match (or exceed) the focal length of the lens. So at 100mm I would want about a 1/100th of a second shutter speed, and thus at 600mm I would want about a 1/600th of a second shutter speed. However, with super telephoto lenses (even a lens that has image stabilization technology built-in, such as the lens I was using) I prefer to be far more conservative.

Because there was relatively good lighting even with the overcast sky, getting a fast shutter speed didn’t require much compromise. I was using an aperture of f/8 in an effort to ensure the sharpest images possible. I wanted the fastest shutter speed I could get, and by boosting the ISO setting up to only 400 I could achieve the maximum shutter speed (1/8000th of a second) for my camera.

I am perfectly comfortable with the degree of noise produced by the camera I was using (a Canon EOS 7D Mk II, http://timgrey.me/tgtv7d2) at an ISO setting of 400. So in this case the decision was easy. I could shoot at f/8 with an ISO setting of 400 and achieve a fast 1/8000th of a second shutter speed. That worked out well, and more importantly the scene was very nice, with snow-covered peaks seeming to blend in to the overcast sky above.

Today’s Question: I was reviewing your photos on 500px, and was struck by the one of cabbage in South Korea. How did you achieve the dark background in that photo where it looks like only the cabbage is lit?

Tim’s Quick Answer: The photo in question can be found here:

https://500px.com/photo/148309649/cabbage-pyramid-by-tim-grey

The photo represents an example of a situation where the light illuminating a subject “falls off” and does not illuminate the background. This was the result of the layout of the scene where I found the cabbage on display, along with the existing lighting conditions.

More Detail: I imagine most photographers are familiar with the style of photographs where a subject (often a flower) is illuminated by flash, and the black backdrop is rendered as a pure black with no texture. These photos are often the result of a technique where flash is used to illuminate the foreground subject, with the flash not being strong enough to illuminate the background. The use of a black backdrop obviously helps make this technique a little easier.

The cabbage display I photographed on Jeju Island in South Korea represented a similar scenario. There were a row of buildings on the street at a public market, and most of the buildings had an awning of some form that covered the entrance to the building. Most of the goods on sale were placed outdoors, but under the awning.

In this particular case the cabbage was on display right at the edge of the awning. It was an overcast day, so soft light illuminated the cabbage, providing a very even overall look without excessive contrast. That soft overhead light wasn’t able to illuminate the area under the awning behind the cabbage, so it was very dark in the background.

In this case I was fortunate to simply happen upon the cabbage display, so there was no need to interact. I do like the photograph, but I don’t think I would have ever had the idea to stack cabbages into a pyramid and light them in a way that provided a dark background. Fortunately for me, in this case the scene was created by others for my benefit.

However, this same overall concept can be used for a wide variety of photographic possibilities. To be sure, you can keep an eye out for scenes that have similar lighting situations without the need for supplemental lighting. But you can also create a similar effect through the use of carefully placed lights and a scene that results in only a key foreground subject being illuminated.

Photographer Joyce Tenneson created some wonderful portraits of flowers that exemplify the technique referred to above in her book “Intimacy”. You can find that book here:

http://timgrey.me/1QHu0aC

Today’s Question: How does the Trim command in Photoshop relate to the Crop tool?

Tim’s Quick Answer: The Trim command is similar to the use of the Crop tool in that it allows you to crop the photo. However, with Trim you are cropping in an automatic fashion based on pixel values found at the edge of the photo, rather than making a specific choice about how to crop the image.

More Detail: When you use the Trim command (found on the Image menu) you are able to choose how to automatically crop the image based on pixels along the edge of the image. If there are transparent pixels along the edge of the image you can choose the “Transparent Pixels” option in the Trim dialog to crop the image to bring all four edges of the image in to the first non-transparent pixel on each side.

You can also choose to trim the image based on the color of the top left or bottom right pixel. For an actual photographic image this would obviously not be very helpful, since each pixel is likely to have at least some degree of variation. So this is more useful for things like screen captures or graphics. For example, if you had a graphic set against a white background, you could use the Trim command to crop all of the “outside” white pixels so that the edge of the image aligned with the edge of the graphic.

Note, by the way, that you do have the option to choose which edges you actually want to trim, with the Top, Bottom, Left, and Right checkboxes. Ultimately, however, the Trim command is mostly helpful for screen captures, graphics, and certain composite images.

It is also important to be aware that the Trim command takes a destructive approach, whereas the Crop tool allows you to take a non-destructive approach to cropping. With the Crop tool you can choose to disable the “Delete Cropped Pixels” checkbox on the Options bar, so that when you crop you are really just reducing the canvas size and hiding the cropped pixels. Those hidden pixels can then always be revealed with the “Reveal All” command found on the Image menu. The Trim command, by contrast, crops by actually removing the trimmed pixels from the image.

Today’s Question: I maintain my catalog and photograph files on an external hard disk to enable me to edit on my laptop and desktop. I am outgrowing my external disk and want to move the catalog and photographs to a new larger external disk. How can I do this so that it will be seamless when using Lightroom (i.e. so that the software knows where to find the catalog and files)?

Tim’s Quick Answer: The task here is actually reasonably straightforward. Put simply, there are two steps involved. First, of course, you’ll want to copy all of the files from the “old” drive to the “new” drive. Then disconnect the “old” drive and assign the same drive letter (on Windows) or volume label (on Macintosh) to the new drive as had been assigned to the old drive. Then when you launch Lightroom again, your catalog and photos will appear right where you left them.

More Detail: In concept there are four things you need to do here. Those are to (1) move the Lightroom catalog to the new drive, (2) move the photos to the new drive, (3) open the catalog in Lightroom from the new drive, and (4) reconnect the photos so Lightroom knows to look for them on the new drive.

As noted above, however, all of these tasks can be streamlined by simply making it look to Lightroom like nothing has changed.

The first step is relatively straightforward, but it can also be a bit time-consuming. That is to copy the catalog and photos to the new hard drive. Be sure to quit Lightroom before you start this process, to ensure that the catalog file is closed before you copy it. You could manually copy all of the contents from the “old” drive to the “new” drive, but you could also use synchronization software (such as the GoodSync software I have recommended before, available at http://timgrey.me/greybackup).

With the Lightroom catalog and photos copied to the new hard drive, you can disconnect the old hard drive and set it aside as a backup. In theory at this point you could simply open the Lightroom catalog that is on your new drive, and then reconnect the photos that will at this point appear to be missing. However, you can streamline this process by making the new hard drive appear to Lightroom as the same as the old hard drive.

For Macintosh users, all you need to do is change the volume label of the new hard drive to match the label for the old drive. This is essentially the “name” of the drive, and you can change that name by simply right-clicking on the drive within the operating system and choosing the Rename option, then typing a new name and pressing Enter/Return on the keyboard. Windows users can find instructions for changing the drive letter for a drive on this page:

http://windows.microsoft.com/en-us/windows/change-add-remove-drive-letter

At this point you simply need to open the new catalog in Lightroom, and you’ll be able to pick up where you left off. For simplicity (and to make sure you’re opening the correct catalog), I recommend going to your new hard drive within the operating system, and navigating to the folder where your catalog is stored. Locate the “lrcat” file that is your actual Lightroom catalog, and double-click that file. That will cause Lightroom to open the catalog, and at this point things should appear exactly as they did before in terms of your catalog and photos, with the difference being that more free space will be available on your new hard drive.

Today’s Question: Do you have a preference for using the “increase/decrease” exposure control in the camera over changing the current ISO value that you are using? It seems (on my Nikon) that using this control is easier (faster) than selecting a different ISO number.

Tim’s Quick Answer: To me the most important consideration here is how you are impacting the final exposure settings. Ultimately, any technique that enables you to quickly achieve optimal settings for the overall lens aperture, shutter speed, and ISO settings is a good technique as far as I’m concerned. I would just caution against allowing one setting to become problematic just because changing a different setting was faster or easier. For example, I wouldn’t want to let the shutter speed get too slow just because it was easier to apply exposure compensation rather than change the ISO setting.

More Detail: I find that most photographers understand the basic concepts related to the “exposure triangle” of lens aperture, shutter speed, and ISO setting. However, I also find that many photographers get confused about when to adjust specific settings, including exposure compensation.

Exposure compensation enables you to apply an adjustment to the overall exposure settings when using an exposure mode other than Manual mode. For example, if you are photographing a snow-capped mountain, the camera’s meter may produce an exposure where the areas covered in snow are completely blown out. You could then apply a negative exposure compensation value to reduce the exposure and retain highlight details in the snow. For example, if you applied a one-stop exposure compensation value you might cause the shutter speed to go from 1/250th of a second to 1/500th of a second, creating a darker exposure.

The ISO setting enables you to have the camera apply amplification to the signal being captured by the image sensor. If you are in the Manual exposure mode, then increasing the ISO setting will indeed cause a brighter exposure, assuming you didn’t change the settings for the shutter speed and lens aperture.

However, in one of the automatic or semi-automatic exposure modes, changing the ISO setting will not change the overall exposure. For example, let’s assume you had the camera set to an aperture of f/8 and a shutter speed of 1/250th of a second at 100 ISO while in Aperture Priority mode. If you then increase the ISO setting to 200, the shutter speed would change to 1/500th of a second. You would have changed the shutter speed along with the ISO setting, but you would not have actually changed the overall brightness of the exposure.

Taking all of this into consideration, my recommendation is to find the best way to achieve optimal overall exposure settings with minimal compromise. In general, I find that involves prioritizing the most important exposure setting based on the circumstances, but reviewing all of the exposure settings to ensure you aren’t creating problems. For example, if you want lots of depth of field you might want to stop the lens down completely. However, that could result in a shutter speed that is too slow. And, of course, you also need to consider the effect of increased ISO settings on the noise levels within the photo.

There is much to consider when establishing the overall exposure settings, but with practice it does get easier to evaluate and decide on those settings more quickly. And again, any technique that enables you to achieve optimal settings quickly is a good technique as far as I’m concerned!

Today’s Question: Sometimes when I’m cropping a photo in Photoshop and I only need to bring the crop in a small amount from the edge, Photoshop won’t let me. When the crop edge is close to the edge of the photo, the crop sticks to the edge of the photo rather than the position I want it. Is there a way to stop this behavior?

Tim’s Quick Answer: There are two basic approaches you might consider, both of which are related. You can turn off the “Snap” feature altogether, or you can temporarily disable this feature while working by holding the Ctrl/Control key on the keyboard.

More Detail: The behavior you’re referring to is called “Snap”, meaning that the object you’re moving (in this case the edge of the crop box) will snap to the edge of the photo when you move close to that edge. This behavior can be helpful when you’re trying to precisely align the crop box along an edge in the photo, rather than just inside or outside the edge of the photo. But of course, this behavior can also be a challenge when it isn’t wanted.

If you hold the Ctrl key on Windows or the Control key on Macintosh, the Snap behavior will be temporarily toggled. Since the Snap option is turned by default, that means that holding the Ctrl/Control key will disable the Snap feature as long as you’re holding that key down. And yes, it really is the Control key (not the Command key) on Macintosh. This is one of the rare situations where the Ctrl key on Windows does not translate to the Command key on Macintosh.

If you find the Snap behavior distracting in general and prefer to turn it off altogether, you can do so by choosing View > Snap from the menu. This will disable the Snap feature in all cases within Photoshop. Note that you need to have an image open in order to access this menu item.

Note that you can also turn off only the “Document Bounds” option for the Snap feature, so that the Crop tool won’t snap to the edge of your photo. This allows you to keep the Snap feature active for other features, such as with Guides and Layers. You can find the various options for a selective Snap feature by choosing View > Snap To from the menu. On a sub-menu you will see the available options, with a checkmark icon indicating which specific options are enabled. You can click on any of those options to toggle them off or on as desired.

Today’s Question: I prefer to download my iPhone captures to a folder on my desktop first, and then import into Lightroom. Sometimes I accumulate several folders full of images that need to be imported. Is there an easy way to import all of those folders at once so I don’t have to import multiple times (once for each folder)?

Tim’s Quick Answer: There are several options available to you, but in this case the easiest approach might be to simply select the multiple folders from the Source panel in the Import dialog. This allows you to select multiple folders of images and import them to the same folder location using the Copy option.

More Detail: On the left side of the Import dialog you are able to select the source of images to be imported. In this case, for example, the source might be a folder on your desktop that contains photos. What many photographers don’t realize is that it is possible to select more than one folder from the Source panel, enabling you to import the photos contained in multiple folders all at the same time.

The approach to selecting multiple folders is the same that you might already be familiar with in your operating system. You can click on the first folder, for example, and then hold the Shift key and click on the last folder to select multiple folders. You can also hold the Ctrl key on Windows or the Command key on Macintosh while clicking in order to toggle the selection of a folder on or off.

In this case you could then use the Copy option at the top-center of the Import dialog to enable you to copy the photos in the multiple folders to the final destination, such as a folder for a current trip on an external hard drive.

You could also select the parent folder (such as the Desktop in this case) and turn on the “Include Subfolders” checkbox at the top of the Source panel. This will cause all photos in all subfolders of the currently selected folder to be included in the import, although you need to be careful to ensure that this approach doesn’t cause unwanted photos or videos to be imported.

You could even automate things further by creating a “watch” folder, so that whenever new images are added to a given folder they can be imported into Lightroom automatically. But again, in this specific example I think simply selecting multiple folders from the Source panel in the Import dialog may represent the best solution.

Today’s Question: How do you set Lightroom to apply automatic Lens Correction on Import?

Tim’s Quick Answer: There are two steps involved here. First, you need to create a preset in the Develop module for the adjustments you want to apply on import (such as Lens Corrections in this case). Then select that preset from the Develop Settings popup in the “Apply During Import” section of the right panel in the Import dialog.

More Detail: To create a preset in the Develop module you establish the applicable adjustment settings for an image, and then save those settings in a preset. In this case, if you want to apply an automatic Lens Corrections adjustment, you would simply establish the desired settings.

So, select an image and go to the Develop module. Then scroll down to the Lens Corrections section and go to the Profile tab. Turn on the “Enable Profile Corrections” checkbox, and set the Setup popup to “Auto”. You can also go to the Color tab and turn on the “Remove Chromatic Aberration” checkbox if you’d like. And, of course, you can add any other adjustments you’d like to apply during the Import process.

Once those adjustment settings are established, you can go to the left panel in the Develop module and click the plus symbol (+) to the right of the Presets heading. In the New Develop Preset dialog, first enter a meaningful name, such as “Add Lens Corrections”. Then click the “Check None” button so that none of the selection options are turned on. Then turn on the checkbox for only those adjustments you want to include with this preset. In this case, for example, you might only turn on the “Lens Profile Corrections” and “Chromatic Aberration” checkboxes. Then click the Create button to save the preset.

In the Import dialog when you next import photos, you can choose your new preset from the Develop Settings popup in the “Apply During Import” section of the right panel in the Import dialog. That setting will remain applied until you change it, so that all imported images will in this case receive the Lens Corrections adjustments.