Ask Tim Grey

Today’s Question: Regarding HDR images, what’s the point? Good monitors now already exceed the dynamic range of printer paper. HDR practitioners claim that HDR images look so much better with more detail in the highlights even when they are displayed on my regular monitor in my web browser. How is this any different than boosting highlight tones with an S-curve?

Tim’s Quick Answer: In the context of how most photographers work with HDR images, the benefit is not about an improved monitor display or print of the image, per se, but to retain information in the image itself that would have otherwise been impossible.

More Detail: Once an HDR image has been fully processed, you can think of it as a normal photograph in the context of displaying it on a monitor or printing the image. The benefit of HDR isn’t about the final output exactly, but more about retaining far greater detail than would have otherwise been possible in the original capture.

In other words, HDR is really about the limitations of our cameras, not about the capabilities of our monitors or printers.

So, when you are photographing a scene that contains too great a difference between the brightest and darkest areas for your camera to capture full detail, you can create an HDR image to maximize the level of detail in the final image. To do so you would bracket exposures, separating each by two stops, with enough exposures to cover the full range from the darkest to the brightest areas of the scene.

Those bracketed exposures can then be assembled into an HDR image. When we talk of a “true” HDR image, where an HDR display would provide a benefit, we’re referring to a 32-bit per channel image. For most photographers their HDR workflow includes processing the HDR with tone-mapping, which converts the 32-bit per channel image to a 16-bit per channel image.

In the process of tone-mapping the image, you’re effectively taking the high dynamic range data from the bracketed exposures and compressing it to fit the range of tonal value for a normal non-HDR photo.

In other words, once you’ve assembled and tone-mapped your HDR image, it is no longer HDR in the mathematical sense. Rather, it is a normal image that through a little bit of photographic and software magic represents a great tonal range than would have otherwise been possible. But the greater tonal range only existed in the scene you were photographing, and the result has now been translated to a normal tonal range.

Today’s Question: When I send a raw file to Photoshop from Lightroom Classic with the Photo > Edit In > Edit in Adobe Photoshop command, it goes straight to Photoshop and not Camera Raw. The file name in the Photoshop window ends in .CR3 [a Canon raw capture format]. When I use the Photoshop command File > Open Recent, it opens in ACR as expected. What gives here? I thought Photoshop could not work directly on raw files!

Tim’s Quick Answer: This is what I’d refer to as an illusion in Photoshop. When you send a raw capture to Photoshop, it isn’t really opened as a raw capture but rather is rendered based on the raw image and adjustments from Lightroom Classic. When you save that image, it will automatically update to a TIFF or PSD file depending on your settings for External Editing in Preferences in Lightroom Classic.

More Detail: When you send a raw capture to Photoshop from Lightroom Classic, it appears as though you’ve opened a raw file directly in Photoshop, bypassing Camera Raw. What actually happened is that you sent image data from Lightroom Classic, rendered based on any adjustments applied in the Develop module.

When the image opens in Photoshop, it isn’t actually a file at all. It is just pixel data in memory. If you quit Photoshop without saving at that point, you would not have a new derivative file on your hard drive. You would only have the original raw capture.

However, if you send the raw capture to Photoshop and then use the File > Save command, the file will be saved as a TIFF or PSD based on the settings established in Preferences in Lightroom Classic. You can review or update those settings in the “Edit in Adobe Photoshop” section of the External Editing tab of the Preferences dialog in Lightroom Classic.

If you later use the File > Open Recent command in Photoshop to re-open a raw capture that had previously been sent to Photoshop, you’re actually opening a raw file and not sending rendered pixel data from Lightroom Classic. As a result, the Camera Raw dialog will appear for that image. However, in the context of Lightroom Classic you should not open a raw capture directly in Photoshop but should rather use the Photo > Edit In command to create a derivative image based on the raw capture and Develop adjustments from Lightroom Classic.

Today’s Question: What does the histogram vertical axis indicate? Is it number of pixels in a certain range or “bucket” of luminance values? What is the peak value; what number of what?

Tim’s Quick Answer: The vertical axis of the histogram shows the relative (not absolute) number of pixels in an image for each tonal value represented by the horizontal axis.

More Detail: While the general concept of the histogram is relatively straightforward, there are a couple of factors that can cause it to be a little confusing.

First off, the horizontal axis represents tonal values in the image, with black at the far left and white at the far right. However, not all tonal values are actually represented. In most cases, the horizontal axis for the histogram is calculated based on only 256 tonal values from black to white. This represents 8-bits per channel for a single channel, effectively meaning that the histogram is calculated as though the image was in black and white and 8-bits per channel even if it is a full-color 16-bit per channel image.

Once the image data is simplified in this way to calculate the shape of the histogram, the pixels are tallied to determine how many pixels in the image represent each tonal value. That number determines the height of the histogram chart on the vertical axis for each tonal value of the horizontal axis. You can think of the histogram in this context as being a bar chart where there are 256 vertical bars along the horizontal axis, with the height of each of those bars representing the number of pixels at each tonal value.

However, the data is manipulated a bit further to improve the overall display of the histogram chart. The chart is generally scaled so that whatever the highest point on the histogram chart is will go to the top of the vertical scale. In other words, the top of the vertical axis can represent a significantly different number of pixels in the image depending on the overall distribution of tonal values in the image.

For example, if you view the histogram for an image that is mostly comprised of very bright pixels, the right end of the histogram will be very tall, and the rest of the histogram will be very low. For an image with a relatively even distribution of tonal values throughout the full range, the entire histogram will be relatively tall. In both cases, the tallest portion of the histogram will extend to the top of the vertical axis.

Of course, different software will use different methods for calculating the histogram display, but the basic concepts outlined above are relatively universal. And of course, if you’re displaying a full-color histogram, the same concepts apply with the difference being that three individual histogram charts are generated for each of the three color channels and then overlaid on top of each other.

Today’s Question: Does the “Merge to HDR” feature in Lightroom Classic provide the same results as Camera Raw?

Tim’s Quick Answer: Yes, the built-in HDR merge feature in Lightroom Classic is equivalent to the same feature in Camera Raw. I therefore recommend using this feature rather than sending bracketed exposures to Photoshop for merging to an HDR image.

More Detail: Photoshop includes the HDR Pro feature for merging bracketed exposures into a high dynamic range (HDR) image. However, in my view this feature is inferior to the Photo Merge feature available in Lightroom Classic and Camera Raw. I therefore recommend using Photo Merge to create HDR images rather than HDR Pro.

For Lightroom Classic users that means assembling HDR images by selecting the bracketed exposures and choosing Photo > Photo Merge > HDR from the menu. That also means avoiding the Photo > Edit In > Merge to HDR Pro in Photoshop command from the menu.

Today’s question was a follow-up to a question about using Camera Raw versus Photoshop for creating HDR images. So, the question is to some extent about whether Camera Raw and the Develop module in Lightroom Classic are equivalent. The answer is that the two are indeed equivalent in terms of processing quality and for the most part in terms of feature parity.

There are times when Adobe releases features in Camera Raw before they are available in Lightroom. However, in general when that happens, we don’t have to wait too long before the feature is available in Lightroom as well.

Today’s Question: During one of your recent presentations you relaunched Lightroom Classic and a screen came up while it was loading that included your logo. Is that a feature available to anyone? If so, how do you make use of it?

Tim’s Quick Answer: Yes, anyone can create a custom splash screen for Lightroom Classic by simply saving an image of up to 900 by 600 pixels in the “Splash Screen” folder.

More Detail: A splash screen is an image that appears while an application is loading, which is relatively common, including with Adobe applications. While it is possible to disable the splash screen with Lightroom Classic (via the “Show splash screen during startup” checkbox on the General tab of the Preferences dialog), it is also possible to create your own custom splash screen.

Besides adding a bit of personalization to Lightroom Classic, a custom splash screen can also provide a bit of branding and promotion such as in situations where your customers might see that splash screen when you’re presenting to them.

To get started, create an image for your splash screen (such as with Photoshop) with pixel dimensions of up to 900 pixels wide by 600 pixels high. Save the image as a JPEG or PNG image. You can then place that splash screen image into the “Splash Screen” folder, the location of which depends on your operating system. Also, note that if you’ve never created a Splash Screen folder, you can create it in the applicable location.

For Macintosh users hold the Option key on the keyboard while choosing Go > Library from the menu (the Library option won’t appear if you’re not holding the Option key). In the Library folder navigate to Application Support > Adobe > Lightroom > Splash Screen.

For Windows users go to the Users folder on your system hard drive (drive C: by default). Then continue navigating to AppData > Roaming > Adobe > Lightroom > Splash Screen.

Again, if the “Splash Screen” folder doesn’t exist you can simply create it. Once your image is in the folder, as long as you’ve not disabled the splash screen in Preferences, you’ll see the splash screen image whenever you launch Lightroom Classic.

Today’s Question: I understand (I think) the logic of the somewhat new “Save a Copy” command, and I’ve gotten used to using it. However, I don’t like that it adds “copy” to the end of my filename, and sometimes I forget to remove it. Is there a way to prevent that text from being added in the first place?

Tim’s Quick Answer: Yes, you can stop Photoshop from appending “copy” to the end of a filename when you use the “Save a Copy” command by turning off the “Do not append ‘copy’ to filename when saving a copy” checkbox in Preferences.

More Detail: The “Save a Copy” command in Photoshop is relatively new and aimed at helping ensure (among other things) that photographers don’t inadvertently save their layered image files in a format that doesn’t support layers, losing all those layers in the process. The “Save As” command will therefore only allow you to select file types (such as TIFF or PSD) that support all the features you’ve used for an image. If you want to save in a file format (such as JPEG) that doesn’t support things like layers, you need to use the “Save a Copy” command.

As noted in today’s question, by default when you use the “Save a Copy” command, the filename will be updated to include “copy” at the end. You can certainly remove that text manually in the “Save a Copy” dialog, but there’s also an option to disable this behavior altogether.

To get started go to the Edit menu on Windows or the Photoshop menu on Macintosh and choose Preferences or Settings followed by “File Handling”. In the “File Saving Options” section turn on the “Do not append ‘copy’ to filename when saving a copy” checkbox. Close the Preferences dialog, and from that point forward the “copy” text will no longer be appended to the filename when using the “Save a Copy” command.

Note that in most scenarios when using the “Save a Copy” command there isn’t any real need to append “copy” to the filename. That’s because when using the “Save a Copy” command you’ll generally be creating a file in a different file format, which means the filename extension will be different from the primary image file. That will generally ensure unique filenames, though you can always modify the default filename if needed or preferred.

Today’s Question: I was told (without explanation, mind you) that I should never store my Lightroom Classic catalog in the Pictures folder in the operating system. My understanding is that the Pictures folder is the default location for catalogs, so is there really any reason I should avoid storing the catalog there?

Tim’s Quick Answer: The only reason I would avoid storing the Lightroom Classic catalog in the Pictures folder is if that folder is being synchronized to the cloud with a service such as iCloud or OneDrive. Otherwise, it is perfectly fine to store the catalog in the Pictures folder or any other convenient location (ideally on a fast storage device such as SSD).

More Detail: In general, you can store your Lightroom Classic catalog in any folder on any hard drive, except for a network storage location. Network storage is not an option for the Lightroom Classic catalog due to the architecture of the software.

However, as a general rule I don’t recommend storing a Lightroom Classic catalog in cloud storage. Storing the catalog in the cloud creates a considerable risk of metadata mismatches and even corruption of the catalog.

To be fair, the issue here isn’t technically the use of cloud storage for the catalog, but rather the risk of accessing the catalog from more than one computer via cloud storage. If you only access the catalog from a single computer and never use any other computer or device to access the catalog, cloud-based storage is generally safe. But if you were to open the catalog from a second computer, even if you only use one computer at a time to access the catalog, there are considerable risks.

If you’re only using Lightroom Classic on a single computer, having the catalog in a folder (such as Pictures) that is being synchronized to the cloud is generally safe. In effect, the catalog files are just being backed up to the cloud, while being updated on the single computer. However, if another computer or device is used to access the catalog files, there is a serious risk of data corruption.

In my own testing with a catalog stored in the cloud, I was able to create metadata mismatches in the catalog instantly by making changes on two computers. I was able to corrupt the catalog to the point it couldn’t be used within about five minutes. To me it isn’t worth the potential risk even if you’re only using one computer, so as a rule I recommend that the catalog not be stored in a folder that is synchronized to the cloud via services like iCloud and OneDrive. Instead, I would store the catalog in a location on the internal hard drive that is not being synchronized to the cloud, or on an external hard drive.

Today’s Question: Can you clarify what is meant by “tone mapping” for HDR images? Why is it an option when using HDR Pro in Photoshop but not with Camera Raw [or Lightroom Classic]?

Tim’s Quick Answer: The term “tone mapping” refers to taking a high dynamic range (HDR) image and converting the pixel date to the tonal and color range of a “normal” 16-bit per channel image.

More Detail: A high dynamic range (HDR) image contains a much wider range of tonal values than a “normal” photograph. The way this is accomplished is by taking the image data from multiple bracketed exposures and blending them into a 32-bit per channel image.

For context, an 8-bit per channel (such as a JPEG capture) can contain up to almost 16.8 million possible color values. A 16-bit per channel image (the maximum for a raw capture, though not all cameras support this high a bit depth) can contain more than 281 trillion possible color values. An image in the 32-bit per channel bit depth can contain color values numbering more than 79 with 27 zeroes, which happens to be more than 79 octillion possible color values.

Of course, the incomprehensibly large number of possible color values for a 32-bit per channel image don’t mean very much in the context of a normal photographic workflow. That’s especially true considering that normal human vision is estimated to be close to matching 8-bit per channel color.

But 32-bit per channel images aren’t intended to provide extreme possibilities in terms of color and tonal values available. Rather, they’re meant to contain huge amounts of image data for special purposes. To put such an image to meaningful use in a photographic workflow it needs to be converted to 16-bit per channel mode, and in the context of converting an HDR image to a “normal” image the term for that process is tone mapping.

So, you can think of tone mapping as the process of taking the incredibly huge range of color and tonal values in a 32-bit per channel HDR image so they fit into a “normal” 16-bit per channel image. This is a process that can be handled directly by software that enables you to create an HDR image in the first place, making it somewhat “invisible” to the user. For example, if you assemble an HDR image in Camera Raw as explained in a previous Ask Tim Grey answer, you are using Camera Raw to perform the tone mapping step to translate the 32-bit per channel HDR data to a 16-bit per channel image.

Today’s Question: I was recently told I should NOT enable profile-based Lens Corrections but SHOULD enable Chromatic Aberration Removal upon import to Lightroom Classic. I am now confused. I am sure I was told just the opposite once. What is the best practice? And how do I re-do my own preset upon import with these items checked or not as needed? Right now I have Lens Corrections on and Chromatic Aberration off.

Tim’s Quick Answer: I prefer to apply profile-based lens corrections as well as chromatic aberration reduction to all images by default when importing into Lightroom Classic. If there are any images where you’re not happy with the results you can always turn one or both of those options off.

More Detail: In general, I find that most images benefit from profile-based lens corrections. I also find that enabling chromatic aberration removal either improves the image or doesn’t have any impact, with no negative consequences of leaving it turned on for all images.

That said, ultimately these options will either be turned on or turned off based on your preferences in general and the needs of an individual photo. Therefore, I recommend deciding whether to apply these adjustments to all images by default based on how likely you are to want to make use of these adjustments.

I tend to prefer enabling both of these adjustments, because I find that in the vast majority of cases they provide an improvement for my photos. If I find an image where the effect is problematic, or that images captured using a particular lens generally benefit from not having the adjustments applied, I can always turn them off.

Conversely, if you find that you generally prefer not to have the adjustments enabled, you could leave them off (which is the default for both) and only apply them when they provide a benefit.

If you have an existing Develop module preset you’ve been applying during import, and you change your mind about which adjustments you want to include, it is easy to make a change. To get started, I recommend selecting an image that you haven’t yet applied adjustments to or resetting the adjustments for an image that can be used for this purpose. Then apply the preset from the Presets section of the left panel in the Develop module to the image. If the “Enable Profile Corrections” and “Remove Chromatic Aberration” checkboxes are not set the way you prefer them, you can turn those checkboxes on or off based on your preference.

Then right-click on the preset on the left panel and choose “Update with Current Settings” from the popup menu. This will update the applicable preset to reflect the changes in settings you made. Just keep in mind that changing the preset will not alter the adjustment settings to images to which the preset had previously been applied, so you may need to make changes to some of your existing photos based on your preferences.

Today’s Question: If I understand correctly, I could assemble an HDR [high dynamic range] image in Photoshop or in Camera Raw. Do you recommend one over the other, or are they the same?

Tim’s Quick Answer: Yes, you can assemble HDR images using either Camera Raw or a feature within Photoshop. I highly recommend Camera Raw because based on my experience, it consistently produces better quality results.

More Detail: Photoshop has long offered the HDR Pro feature for combining multiple exposures into an HDR image. However, I consistently find that Camera Raw provides superior results with a more streamlined workflow, and so highly recommend Camera Raw over HDR Pro for assembling HDR images.

If you want to test HDR Pro for yourself, you can select the multiple bracketed exposures you want to merge into an HDR image within Adobe Bridge. Then go to the menu and choose Tools > Photoshop > Merge to HDR Pro. The selected images will be opened into a layered image in Photoshop, and the HDR Pro dialog will appear. You can apply the tone-mapping directly with HDR Pro by selecting “16 Bit” from the Mode popup. However, in general I recommend choosing “32 Bit” and then keeping the “Complete Toning in Adobe Camera Raw” checkbox turned on. This enables you to complete the tone-mapping for the HDR image using Camera Raw. Of course, you can also simply perform all processing in Camera Raw, which I think makes more sense and, in my experience, produces better results.

To create an HDR image in Camera Raw you can first select all the exposures for the HDR image in Adobe Bridge. Then double-click on any of the selected raw captures to open them in Camera Raw. On the filmstrip in Camera Raw select all the images, then either right-click on one of the images or click the “more” button (the ellipsis icon) at the top-right of one of the thumbnails. From the popup menu choose “Merge to HDR”.

This will bring up the HDR Merge Preview dialog, where you can configure the settings for creating the initial HDR image. Click the Merge button, and the HDR image will be created and opened in Camera Raw. You can then use all the available adjustments to fine-tune the result. You can then click the Open button at the bottom of the Camera Raw dialog to open the HDR image in Photoshop, save the image, and apply any additional adjustments you’d like.