Smart Preview Size

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Today’s Question: How much extra disk space in my catalog do smart previews consume?

Tim’s Quick Answer: Smart Previews in Lightroom consume a surprisingly small amount of storage space. As a general rule you can expect Smart Previews to consume somewhere around 1MB per image, with your specific results depending on the nature of the images being processed.

More Detail: A Smart Preview is essentially an Adobe DNG file resized to no more than 2,540 pixels on the long side. Because there is lossless compression applied, the file sizes are quite small. In my testing I have found that the Smart Preview file size represents approximately 1MB per image. This total can vary considerably based on the types of image files you’re working with, and the effectiveness of compression based on the contents of the photos.

But I think the 1MB per image value represents a good general estimate. That, in turn, translates into about 1GB of storage space for every 1,000 images. For a catalog with 100,000 images, you could expect the data file for your Smart Previews to be about 100GB.

Again, these are just rough estimates, and the actual result can vary significantly based on the types of source images you’re using along with other factors. But the point is that compared to the storage requirements for the original captures, Smart Previews are quite small and manageable.

Missing Feature

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Today’s Question: You said: “On the Performance tab you can then turn on the ‘Use Smart Previews instead of Originals for image editing’ checkbox.” I do not see this check box when doing the above. What should I be doing? I generate smart previews when importing new images.

Tim’s Quick Answer: The Lightroom feature that enables you to leverage Smart Previews (rather than the source images) to speed up your workflow in the Develop module was added with version 2015.7 of Lightroom. Updating to the latest version will therefore make this feature available to you.

More Detail: One of the “workflow” changes introduced when Adobe introduced the Creative Cloud version of most of their software applications is the more frequent updates that are available. I have found that many photographers haven’t developed the habit of keeping their Creative Cloud applications up to date.

It is worth noting that a variety of small but helpful features have been released with various updates, and so it is easy to miss some important features in the context of what seems to be a “small” update.

I certainly recommend in most cases that you not update immediately when a new version becomes available. At times a new update may break an existing feature or cause other problems that can impact your workflow. It is therefore a good idea to wait at least a few days, and perhaps check to see if you can find any reports of problems related to the new update. But by updating within a reasonable time you’ll ensure you have access to all of the latest features and updates that are now provided on a more frequent basis as part of the Adobe Creative Cloud subscription model.

Faster with Smart Previews

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Today’s Question: You said [in yesterday’s Ask Tim Grey eNewsletter] that you could improve performance by preferring the use of Smart Previews in Lightroom. What does that mean and how do you enable it?

Tim’s Quick Answer: You can improve (often significantly) the performance of Lightroom when optimizing photos in the Develop module by using Smart Previews (rather then the source images) as the basis of those adjustments. To enable this option turn on the “Use Smart Previews instead of Originals for image editing” checkbox on the Performance tab of the Preferences dialog in Lightroom.

More Detail: The Develop module in Lightroom makes use of the original image file as the basis of the adjustments you apply. That helps ensure you see the most accurate previews possible, but can also result in degraded performance. It is possible, however, to use Smart Previews as the basis of your adjustments in the Develop module, which will generally improve performance (sometimes quite significantly).

The first step is to generate Smart Previews for all images you want to work with in this way. You could, for example, select all images in your entire Lightroom catalog and then choose Library > Previews > Build Smart Previews from the menu to generate Smart Previews for those images. You can also build Smart Previews as part of the import process by turning on the “Build Smart Previews” checkbox in the Import dialog.

With Smart Previews built for your images, you could simply make the source images unavailable to automatically make use of the Smart Previews. For example, if the source images are on an external hard drive you could disconnect that hard drive from the computer. Lightroom will then use the Smart Previews in the place of the source images when you work in the Develop module.

In addition, you can prioritize the use of Smart Previews in the Develop module even when the source image files are available, in order to improve performance. You can enable this option in the Preferences dialog, which you can bring up by choosing Preferences from the Lightroom menu on the Macintosh version or from the Edit menu on the Windows version. On the Performance tab you can then turn on the “Use Smart Previews instead of Originals for image editing” checkbox. Lightroom will then use the Smart Preview (if available) within the Develop module, even if the source image is currently available. Note that the preview may not be as accurate, but performance will be improved.

Smart Preview Sync

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Today’s Question: Regarding working with Lightroom on two computers and one external hard drive, can’t you work on the smart previews on either device while not connected to the drive and then sync them when connecting?

Tim’s Quick Answer: Not really. With this type of workflow you would still run into problems with the synchronization of the overall Lightroom workflow.

More Detail: Let’s assume you are working with a Lightroom catalog on your computer’s internal hard drive, with your photos stored on an external hard drive. Even if the external hard drive is disconnected, the standard previews generated by Lightroom would enable you to review your photos, and even update metadata in the Library module. However, in this situation you would not be able to work with your photos in the Develop module until you reconnected the external hard drive.

If you generate smart previews for your photos, however, then you would be able to work in the Develop module even when the external hard drive containing the source images is disconnected. You could even export copies of your photos based on the smart previews. When you reconnect the external hard drive the updates will be synchronized based on the source photos.

However, working with two computers would still be problematic.

Today’s question was in response to a question addressed in a previous edition of the Ask Tim Grey eNewsletter. That question related to the approach of storing your Lightroom catalog on an external hard drive with the source image files, so that you could switch between two computers by simply moving the external hard drive between those two computers.

However, this approach does not enable you to work with smart previews on both computers interchangeably. The smart previews are connected to the actual catalog files, and so you would only have access to the smart previews if you had access to the catalog. In other words, you would need to have the external hard drive connected to the computer in order to access the catalog, which in turn means the external hard drive needs to be connected in order to access the smart previews. However, in this scenario the source images would also be available, so you would not derive a significant benefit from the smart previews (other than a potential performance benefit based on prioritizing the use of the smart previews).

Lightroom does not inherently support working with the same catalog across multiple computers. You can move a catalog between computers (such as by keeping the catalog on an external hard drive) to work around this. It is also possible to use an online synchronization service such as DropBox (https://www.dropbox.com) to enable a workflow across two or more computers. However, there are also some inherent risks with this approach, so it is not something I would generally recommend.

RAW Support

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Today’s Question: Can I update Photoshop CS6 to support new RAW capture formats, such as for the new camera I just bought? I would rather not subscribe to “CC” if I can avoid it.

Tim’s Quick Answer: Adobe is no longer adding support for new RAW capture formats in Adobe Camera Raw for Photoshop CS6. You will either need to subscribe to the Creative Cloud version of Photoshop, or use the Adobe DNG Converter to convert your RAW captures to the Adobe DNG format.

More Detail: When Adobe releases a new major update to Photoshop, updates to older versions of Photoshop (if they are available at all) are generally limited to bug fixes. Support for the latest RAW capture formats is generally limited to the current release of Photoshop (and by extension Adobe Camera Raw) or Lightroom.

Therefore, to be able to process the latest RAW capture formats supported by Adobe Camera Raw (or Lightroom) you need to be using the latest major version of the software. In the context of Photoshop, that means you need to have at least a Creative Cloud Photography Plan subscription so you will have access to the latest updates to Photoshop.

One workaround that works in most cases is to convert your RAW captures to the Adobe DNG (Digital Negative) format, using the free Adobe DNG Converter. Images converted to the Adobe DNG format are supported by older versions of Adobe Camera Raw, including the version available for Photoshop CS6. Thus, in most cases you can convert RAW capture formats that are not supported in Photoshop CS6 to the Adobe DNG file format, and then process the DNG file with Adobe Camera Raw.

Dithering a Gradient

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Today’s Question: What is “dither”, and should I enable this option when creating a gradient in Photoshop?

Tim’s Quick Answer: Dithering in the context of a digital image refers to the introduction of “noise” to help prevent issues such as posterization. In the context of a gradient, dithering involves the blending of various color and tonal values to help maintain the appearance of a smooth transition.

More Detail: When you are working with a 16-bit per channel image, dithering is an unnecessary concept. However, for 8-bit per channel images dithering can certainly become a very real concern in certain contexts. The Gradient tool is a good example of when dithering can be helpful.

A gradient by definition is aimed at producing a smooth transition between one value and another. For example, let’s assume you are attempting to create a gradient that transitions from white to black over a range of 3,000 pixels, or around 10 inches assuming a 300 pixel-per-inch print resolution.

If the image containing this gradient is an 8-bit per channel image, there are only 256 shades of gray available to create a white-to-black gradient. That, in turn, means that each individual tonal value on the gradient will require just about twelve pixels. In other words, there will be a series of bands of individual tonal values defining this gradient, each being 1/25th of an inch in size.

By enabling the Dither option (available as a checkbox on the Options bar for the Gradient tool) you can help to create a smoother appearance for that gradient. Instead of having bands of various shades of gray that are 1/25th of an inch wide, you will have the appearance of a smoother gradation thanks to the dithering.

So, dithering is not necessary for 16-bit per channel images in the context of a normal photographic workflow. However, it can be very helpful to ensure that dithering is enabled for any image being adjusted in the 8-bit per channel mode.

What is PNG?

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Today’s Question: We had pictures taken at our 50th and the photographer provided them in PNG file format. What is it and how do I convert to NEF or JPG?

Tim’s Quick Answer: The Portable Network Graphics (PNG) image format is actually a very good image format that I consider to be (in most respects) better than the JPEG image format. You could certainly use a variety of different software tools to create a JPEG image based on the PNG, but you may not need to. And there is no way to convert an image file such as PNG or JPEG to a RAW capture format such as Nikon NEF.

More Detail: The PNG image format supports lossless image compression and 16-bit per channel data, which is a considerable advantage in terms of image quality compared to JPEG image files. Frankly, the only real reason to use JPEG instead of PNG is to obtain a smaller file size through the lossy compression employed by the JPEG image format, which does degrade image quality to some extent.

I’m not really sure why the JPEG image format managed to gain wider adoption than the PNG file format. Part of the issue was a lack of support for the PNG format in various software applications. In fact, Adobe Lightroom didn’t even support the PNG format until version 5.

I would suggest keeping the PNG files as your “original” image format, creating other image file types only as you need them. You can use Lightroom to export a copy of the PNG files as JPEG (or other format) images, or use Photoshop or other software to save a copy of the image in a different format. But in most scenarios that probably won’t be necessary, and the PNG files will provide you with a good source in terms of overall image quality.

You could, of course, contact the photographer to see if they were using RAW capture, and if so ask if it would be possible to obtain the original RAW captures for at least your favorite images. But in many cases a commercial photographer will be reluctant to provide the RAW captures, preferring to provide only processed images to the client.

HDR and Expose to the Right

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Today’s Question: Your advice [in Tuesday’s webinar presentation] to “expose to the right” on the histogram made sense, but it triggered a question immediately regarding HDR [high dynamic range imaging]. I understand your point about noise being a major reason for the advice to expose to the right. But does HDR override that advice given that the series of separate HDR frames include a wide range of exposures? I assume it does, and for the most part, I don’t see the noise problem you illustrated today.

Tim’s Quick Answer: With a good approach to capturing the original frames for your final HDR exposure, you will indeed achieve the basic benefit of “expose to the right”. This issue is less critical with HDR captures, but that is in part because of the blending of multiple exposures.

More Detail: My two key recommendations for capturing the individual frames for an HDR image address the benefits of the “expose to the right” approach, which can help maximize detail and minimize noise in the final image.

First, I recommend that for an HDR sequence you start with an exposure that is as bright as possible without losing highlight detail. In other words, your first exposure is an “expose to the right” capture for the overall scene. Of course, if HDR techniques are required this exposure will be lacking shadow detail.

My second recommendation relates to how many exposures to capture. In short, I want to capture enough images that the final image (the brightest of the sequence) shows the far left end of the histogram display at about the midpoint of the histogram display. In other words, areas of true black in the scene would be rendered closer to middle gray in the final capture.

By having this extended range of information that generally covers the full tonal range of the scene, you’ll ensure that you have good information (light) to blend together. That, in turn, will help ensure minimal noise for your final result.

Again, this isn’t a major concern for HDR imaging under normal circumstances, but by taking the approach outlined above you’ll be sure to gain the benefits of the “expose to the right” approach for your HDR captures.

Missing Panel in Photoshop

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Today’s Question: While in Photoshop I was exploring the panels at the right side of the screen with attention focused on the Layers tab. I decided to click on the tab and drag it into my image area, which was fine. The only thing was, I clicked the small “x” at the top left corner of this floating panel thinking this would cause it to go back to its place at the bottom right corner of the screen. It disappeared! I have had a search through the help section of the application but have turned up blank so far. Can you please advise me on this?

Tim’s Quick Answer: You can bring back any “missing” panels in Photoshop by choosing the panel by name from the Window menu. So in this case you can choose Window > Layers from the menu to bring up the Layers panel.

More Detail: All of the various panels available in Photoshop can be found on the Window menu. The panels can be docked to the side of the main Photoshop window, left floating within the interface, or minimized to a iconic button you can click to view the full panel.

As noted in the question, if you drag a tab for a docked panel you can “drop” it elsewhere in the interface to make it a floating panel. Clicking the “X” at the top-left corner of the floating panel will close the panel. But you can bring any panel back to view by selecting it from the Window panel. Note that a checkmark to the left of a panel name on the Window menu indicates that the panel is already visible within Photoshop.

To help maintain your preferred interface arrangement within Photoshop you can save a custom workspace. Start by configuring the panels within Photoshop the way you want them. Then choose Window > Workspace > New Workspace from the menu. In the New Workspace dialog you can type a name for the workspace, perhaps using your own name or the nature of the tasks you’ll be performing with that workspace configuration.

Once you’ve saved a workspace, anytime you make changes to the panel layout you can reset to the saved configuration by choosing Window > Workspace > Reset. Note that this “Reset” command on the menu will also include the name of the saved workspace you are currently using.

Selecting Out of Gamut Colors

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Today’s Question: I realize you can use soft proofing in Photoshop to see which colors in the image are out of gamut based on a particular printer profile. But is there then an easy way to select those out of gamut areas so an adjustment can be applied to only those areas, leaving all other pixels as they are?

Tim’s Quick Answer: You can actually select out of gamut colors very easily using the “Out of Gamut” sampling option available with the Color Range selection command.

More Detail: The Color Range command in Photoshop is generally used for creating a selection of a specific range of color values in an image, often to select a particular object or area within the photo. However, there are also additional sampling options available for the Color Range command, including an option to select out of gamut colors.

The first step is to configure soft proofing based on the desired output conditions. To do so, choose View > Proof Setup > Custom from the menu. In the Customize Proof Condition dialog that appears, set the applicable output profile using the “Device to Simulate” popup. Set the desired Rendering Intent (in most cases I recommend using “Relative Colorimetric”), and turn on the Black Point Compensation checkbox. Adjust any other settings as desired, and click the OK button to apply the change and enable the Proof Colors view option.

If you’d like to see a preview of which areas of the image are out of gamut, you can choose View > Gamut Warning from the menu. Then, to get started creating a selection of the out of gamut areas, you can choose Select > Color Range to bring up the Color Range dialog.

Within the Color Range dialog click the Select popup, and choose “Out of Gamut” from that popup. You can then click the OK button to close the Color Range dialog and create the selection of the out of gamut colors in the photo.

You can then, for example, add an adjustment layer to apply an adjustment to the selected out of gamut areas of the photo, or otherwise work specifically with that portion of the image.