JPEG Quality

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Today’s Question: If I understand correctly, the Quality slider in the Export module of Lightroom is the primary controller of file image size. I wonder if you could explain the Quality slider in more detail and what is an ideal image file size (kb) range for optimizing web images in terms of preserving image quality and page load speed across various devices.

Tim’s Quick Answer: The Quality setting for JPEG images relates to the degree of compression applied, which in turn impacts the size of the JPEG image file. A higher setting for Quality results in a larger file size, and a lower setting for Quality results in a smaller file size. For online sharing or other situations where you want to strike a balance between file size and image quality, I recommend a Quality setting of 80% in Lightroom, or a value of “8” (eight) in Photoshop or other applications.

More Detail: Because of the nature of JPEG image compression, it is difficult to predict exactly how large the final file will be. Images with greater detail will generally not compress as well, and thus will have a larger file size when saved as a JPEG file. Images with less detail (more areas that have minimal texture and many pixels of the same or similar color) will have a smaller file size when saved as a JPEG.

JPEG compression essentially involves simplifying the information in the image being saved. Generally speaking this process involves dividing a photo into blocks of sixteen by sixteen pixels (256 pixels per block) and then simplifying the information within those blocks. At a lower the Quality setting, the simplification process will be more aggressive. With more simplification of the image data, the file size is smaller.

One way to think of this is with an illustrative analogy. Imagine that one block within a photo contains only blue pixels. Specifically, every single pixel in that block is exactly the same shade of “sky blue”. Instead of having to repeat “sky blue” as a pixel color for all of the 256 pixels in that block, the information can be saved to the file as “256 sky blue pixels”. Again, this is an over-simplification of what’s actually happening, but it gives you a sense of the process.

This process of simplifying the information within a JPEG using blocks of pixels is a key reason that a low Quality setting results in lower image quality. With stronger compression, there is greater simplification of the information within the image, and the grid structure of the 256-pixel blocks can become visible in the image.

Thus, there is an inverse relationship between file size and image quality. At a higher Quality setting the file size will be larger, but the quality will be greater with less risk of compression artifacts. As noted above, it is difficult to predict the final file size with great precision. Instead, I recommend making your decision based on a determination of the importance of image quality relative to file size.

I recommend using a Quality setting of 80% in Lightroom (8 in other applications) when file size is a key concern. When image quality is the highest priority, I recommend saving in a file format such as TIFF without any destructive compression, or using the highest value for Quality if you need to use a JPEG format to control the final file size.

High Pass Sharpening

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Today’s Question: What are the situations when “High Pass Sharpening” [in Photoshop] might be a good choice over “Smart Sharpen” or other methods?

Tim’s Quick Answer: The technique known as “High Pass sharpening” is a technique I consider to be more about emphasizing texture and detail in a photo, rather than sharpening to compensate for softness in a photo. Thus, I would recommend the High Pass technique when you are focused on enhancing detail and contrast in a photo. Note that the technique produces an effect that is very similar to that provided by the Clarity slider in Adobe Camera Raw and Lightroom, among other software.

More Detail: The High Pass sharpening technique gets its name from the High Pass filter in Photoshop. Using the High Pass technique enhances midtone contrast in an image, helping to emphasize detail. If you’re familiar with the basic concepts behind sharpening in most imaging software, you can think of the High Pass technique as being similar to sharpening, but with a higher effective Radius setting.

In other words, like sharpening, the High Pass technique enhances contrast along existing contrast edges in a photo, but it does so across a larger area. In other words, the contrast being enhanced along edges in a photo spreads out from those edges more than would otherwise be the case with typical sharpening.

In fact, with the Unsharp Mask filter in Photoshop you can achieve a result very similar to High Pass sharpening. Simply set a high value for the Radius setting (around 20 pixels or so) and a relatively low value for Amount (around 20% to 50%). And, as noted above, similar results can be achieved with the Clarity slider in Lightroom and Adobe Camera Raw, as well as the newer Dehaze slider in these two software applications.

For those unfamiliar, the High Pass technique is relatively easy to accomplish in Photoshop. Start by creating a copy of the Background image layer, which can be done by dragging the thumbnail for the Background layer to the “Create a New Layer” button (the blank sheet of paper icon) at the bottom of the Layers panel. Then set the Opacity to 50% for this layer, using the control at the top of the Layers panel. Change the blend mode from the default of “Normal” to “Overlay” using the popup at the top-left of the Layers panel. Then choose Filter > Other > High Pass from the menu, and set the Radius value to around 10 pixels, adjusting to taste. Click OK to apply the filter, and then fine-tune the Opacity setting for the Background Copy layer.

Delete Catalog After Upgrade?

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Today’s Question: I just upgraded from Lightroom 5.7 to Lightroom CC. In the process, it appears that my catalog was copied, upgraded and renamed from Photos1 to Photos1-2, so now I have two catalogs. Is there any reason to save the Photos1 catalog or can I safely delete it?

Tim’s Quick Answer: Provided the new catalog is working properly, there is no reason to retain the older version of your catalog other than as a “worst case scenario” backup. So once you’re confident the new catalog is in good shape and you have backed up the new catalog, you can delete the old catalog.

More Detail: When you upgrade to a new “major” release of Lightroom, your existing catalog needs to be upgraded as well, so that the catalog reflects the new features and options available in the new version of Lightroom. As part of that process, your new version of Lightroom will create a new catalog that is essentially an upgrade to your existing catalog. In other words, your previous catalog will remain as it is, and a new catalog will be created that contains all of the information from your existing catalog.

While this is a good approach in terms of being cautious, it does mean that you may end up with several “extra” catalogs, by virtue of having catalogs from older versions of Lightroom. As far as I’m concerned, once you’re confident that your new catalog is in proper working order and you’ve backed up the new catalog, there is no real benefit to retaining old copies of catalogs from older versions of Lightroom.

Lightroom on Two Computers

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Today’s Question: I have the problem that my desktop computer (iMac running OS 10.6.8) will only run Lightroom 4 and my Mac laptop will run the newest version. Is there a way that I can work on my images in Lightroom from both computers? Do I need to dedicate all of my image processing to one computer?

Tim’s Quick Answer: There are two issues here. First, more recent versions of Lightroom require a newer version of the Macintosh operating system than you are running on your iMac, so if your iMac doesn’t support an update then you can’t run Lightroom on that computer. Second, Lightroom doesn’t really support a workflow that involves using the same catalog on two computers. Therefore, I generally recommend using a single computer as your “home base” for using Lightroom.

More Detail: The first limitation may be a more significant issue for you. It is not possible to work with a single catalog for both Lightroom 4 and Lightroom 6, for example. So you would need to be using the same version of Lightroom on both computers in order to be able to work with the same catalog across more than one computer.

Once you have two computers running the same version of Lightroom, there are still some challenges involved. Perhaps the simplest solution would be to keep your Lightroom catalog on an external hard drive along with the photos being managed by your catalog. This approach would enable you to move the external hard drive to the computer you want to use at any given moment. You can open the catalog in Lightroom from your external hard drive, and of course access the images that are also stored on that external hard drive.

In theory it is also possible to store your catalog using an online synchronization solution such as DropBox (https://db.tt/AX4h8FwU) to synchronize a catalog that can be accessed across multiple computers. I’m not entirely comfortable with this approach due to the potential risk of getting out of sync on one or more computers. But it is an option that some photographers have successfully implemented.

For most photographers who need to access a Lightroom catalog on more than one computer, I recommend storing the catalog and photos on an external hard drive, and moving that hard drive from one computer to another as needed. However, it is also important to keep in mind that this approach can result in a potentially significant degradation in overall performance within Lightroom. Therefore, you’ll need to weigh the benefits of being able to move among more than one computer with the potential negative consequences, such as reduce performance.

Personally, I’ve opted to consolidate my workflow to a single computer, with my Lightroom catalog stored on my laptop computer and my photos stored on an external hard drive. But, of course, this isn’t necessarily the best solution for all photographers.

Moving Unmanaged Photos

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Today’s Question: [When attempting to move photos to a new hard drive in Lightroom, as addressed in a prior edition of the Ask Tim Grey eNewsletter,] What if some of the photos in the folders being moved are not in the Lightroom catalog?

Tim’s Quick Answer: When you move photos from one hard drive to another in Lightroom, only the photos actually included in the Lightroom catalog will be moved to the new hard drive. Any photos on the drive that are not being managed in Lightroom will be left behind on the existing hard drive.

More Detail: It obviously makes sense that moving photos within Lightroom would only affect photos that are actually being managed in your Lightroom catalog. This also underscores one of the reasons I highly recommend that if you are using Lightroom to manage your photos, you should use Lightroom to manage all of your photos. In other words, from my perspective it is best not to have photos included in your photo storage structure without also having those photos included in your Lightroom catalog.

If there is any chance that some of the photos stored on the existing hard drive are not included in your Lightroom catalog, it is important to review the existing hard drive after moving photos to your new drive, in order to make sure there aren’t any photos or folders “left behind”.

If there are photos left behind on the existing hard drive after you’ve moved photos to a new hard drive within Lightroom, you’ll need to determine what to do with those photos. If the photos aren’t in your Lightroom catalog because they are “rejects”, you could certainly delete those remaining photos if that is your preference. You could also import those photos into Lightroom, moving them to the new storage location in the process by using the “Move” option in the Import dialog.

I should add that this overall topic is also (I think) a reminder of an issue that some photographers have been confused about. The Folders section of the left panel in the Library module in Lightroom is a reflection of your existing storage structure for your photos. Thus, moving photos within Lightroom will cause photos to be moved on your hard drive. And, as noted above, photos that aren’t in Lightroom won’t be affected by what you do within Lightroom.

Moving Photos in Lightroom

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Today’s Question: I have my photos stored on my computer’s hard drive, My computer is giving me nasty warning signs that I am running out of space. I need to move the photos from the computer to an external hard drive, and I need to do it from within Lightroom, as you impressed upon us. You told us to create a new folder for the external hard drive and drag the photos into it, but I’m having difficulty setting that up. The external hard drive is not showing up in Lightroom. Could you review the process for me? I would appreciate your help with this.

Tim’s Quick Answer: The “trick” here is to create a new folder on the new hard drive from within Lightroom. Doing so will cause that new folder (and thus the new hard drive) to appear in the Folders list in the Library module in Lightroom, even though Lightroom is not yet managing any photos on that new hard drive.

More Detail: To create the new folder, first make sure the new hard drive is connected to your computer and otherwise ready for you to copy photos too. Then, in the Library module in Lightroom, click the “plus” symbol to the right of the Folders list on the left panel. From the popup menu that appears choose “Add Folder”.

In the dialog that appears, navigate to the new hard drive, and click the “New Folder” button. Type a name for that folder (such as “PHOTOS”), and press Enter/Return on the keyboard to create the actual folder. Then click the “Choose” button to confirm the new folder and close the dialog.

At this point the new folder (and thus the new hard drive) will appear on the list under Folders on the left panel in the Library module. You can then drag-and-drop folders from the original location to the new location. You can even select multiple folders from the list by clicking the first folder you want to select and then holding the Shift key while clicking the last folder you want to select.

I should hasten to add that it is important to make sure you have a good backup copy of all of your photos before performing this task, just in case anything goes wrong in the process.

More details about this process (and more tasks for cleaning up your Lightroom catalog) can be found in my video training course “Cleaning Up Your Mess in Lightroom”, which is available in the GreyLearning video training library (http://www.greylearning.com).

Evaluating Alignment

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Today’s Question: This may be a bit of a stretch, but… The subject of blend modes reminded me of a technique that I think involved a blend mode [in Photoshop] to determine whether the frames of a panorama are aligned well. I know there are automatic options for assembling composite panoramas, but I like to put them together myself. Can you remind me of the blend mode option, if I’m even remembering these few details correctly?

Tim’s Quick Answer: It is indeed a blend mode that provides the feature you’re looking for in Photoshop, where you’re able to see the degree to which the pixels in two overlapping layers actually match. That blend mode is the Difference blend mode.

More Detail: To use the Difference blend mode for evaluating the alignment of two image layers, simply change the blend mode for the upper image layer on the Layers panel. So, you can click the thumbnail for the upper of the two layers you want to compare, to make sure that layer is active. Then click the popup at the top left of the Layers panel (the popup has the default value of “Normal”) and choose Difference.

With the Difference blend mode, any pixels that are an exact match on the upper and lower layer will appear as black. Any pixels that aren’t an exact match will appear as a color that differs from black to the degree there is a “mismatch” between the pixels.

In other words, when using the Difference blend mode for this purpose, your goal is to have as much black in the image as possible. You can move the image layers, resize the image layers, transform the image layers, and more, in order to achieve the best alignment possible.

While I do find that various software tools (including Photoshop) do a great job of automatically assembling and aligning the individual frames for a composite panorama, I also find the Difference blend mode to be tremendously valuable when I choose to take a “manual” approach for any reason.

When to Shoot HDR

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Today’s Question: How do I know when I should be capturing several images for an HDR (high dynamic range) instead of just a single exposure?

Tim’s Quick Answer: Conceptually, whenever the histogram display for a single exposure shows clipping at both the black and white ends of the histogram (or significant clipping at one of the two ends), you might want to capture bracketed exposures to possibly assemble into a high dynamic range (HDR) image.

More Detail: With practice, of course, you can learn to anticipate when the overall contrast (or dynamic range) of the scene you are photographing is significant enough that a single exposure won’t be able to contain the full range of tonal values in the scene. The limitations in terms of dynamic range vary from one camera to the next, but over time you will develop a sense of when you’re near (or past) the limitations of your camera.

Of course, just because the dynamic range of the scene is beyond the capabilities of your camera to record in a single capture doesn’t mean you should create an HDR image. A photo with clipping of detail in the darkest shadows could simply be a dramatic photo, and a photo with clipping of highlights could simply be a very nice “high key” photo.

That said, my approach is to capture a sequence of bracketed exposures whenever I know (or my camera’s histogram display tells me) that the full dynamic range of the scene can’t be captured with a single photograph. This provides the flexibility of deciding later whether I want to create an HDR image or simply work with the best of my various exposures.

So, there is an element of experience in terms of being able to anticipate when the dynamic range of a scene exceeds the capabilities of your camera. There is also an artistic decision to be made here in terms of how you will interpret the scene. But in general I prefer to have bracketed exposures whenever the scene has a high dynamic range, so I have more flexibility when processing my photos later.

Overlay versus Soft Light

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Today’s Question: Is there a difference between the Overlay and Soft Light blend modes in Photoshop? I see some people using one versus the other with the same basic techniques.

Tim’s Quick Answer: The Overlay and Soft Light blend modes are both “contrast” blend modes that enable you to achieve both a brightening and darkening effect with an underlying image at the same time. The effect of both is essentially the same, with the difference being that the Overlay blend mode creates a somewhat stronger effect than the Soft Light blend mode.

More Detail: The first three categories of blend modes in Photoshop enable you to apply a darkening effect (with Multiply being the first of these blend modes), a lightening effect (with Screen being the first of these blend modes), or both (with Overlay being the first of these blend modes).

I refer to the blend modes that can both lighten and darken as the “Contrast” blend modes. There are a variety of situations where you might use a contrast blend mode, such as dodging and burning by painting onto a separate layer or reducing haze and enhancing detail with the “High Pass” sharpening technique.

With a contrast blend mode, any pixels on the layer to which you have applied the blend mode that are lighter than middle gray will have a lightening effect on the underlying image. Any pixels that are darker than middle gray will have a darkening effect on the underlying image. So if you have both light and dark areas in the layer you’ve applied the contrast blend mode to, you’ll brighten some areas and darken others, leading to (generally speaking) increased contrast.

The Overlay blend mode simply applies a stronger effect than the Soft Light blend mode. Thus, some photographers prefer one over the other. I, for example, prefer the Overlay blend mode because it provides a stronger effect.

It is important to keep in mind, however, that with many of the techniques where you might employ a contrast blend mode, you’re going to reduce the Opacity setting for the layer to which the blend mode is applied. Therefore, the final effect can be the same with either Overlay or Soft Light, with the only difference being the specific Opacity setting you use to achieve the final effect.

In general you can think of the Overlay and Soft Light blend modes as being interchangeable. Just keep in mind that the Overlay blend mode provides a stronger contrast effect than the Soft Light blend mode.

Photos to Facebook

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Today’s Question: I’m new to Facebook, and was wondering when you post images from Ligthroom directly to Facebook, can you have multiple pictures in one timeline event? I see you can post to photo albums, etc. But each image is a separate timeline event. With some posts I would like to group more than one picture to a single timeline event.

Tim’s Quick Answer: Yes, you can publish multiple photos from Lightroom to Facebook as a single event on your timeline. You just need to create a new collection for that task, and then publish all of the photos in that collection at the same time. Facebook will then include all of the photos published as part of that process in a single timeline event.

More Detail: You first, of course, need to authorize Lightroom to access your Facebook account, which you can do by clicking the “Set Up” link to the right of Facebook in the Publish Services section of the left panel in the Library module in Lightroom.

Once you’ve configured Lightroom to be able to access your Facebook account, the next step is to create a collection for publishing a group of photos to Facebook. You can start by selecting the photos you want to include on that collection. For example, you might filter your photos so you can only see those you’re interested in sharing on the Filmstrip. Then select the specific photos you want to share to Facebook.

With those images selected, right-click on the Facebook item in the Publish Services section of the left panel and choose “Create Collection” from the popup menu that appears. In the Create Collection dialog, configure the settings for this collection, including the details in the “Facebook Album” section, such as the “Album Name”. When you’re finished configuring these settings, click the Create button to actually create the collection.

Finally, viewing the new collection under Facebook in Publish Services, and with the Grid view enabled (which you can do by pressing “G” on the keyboard if you were in the Loupe view), click the “Publish” button toward the top-right of the images in the Grid view display. This will cause all of the photos to be published to the Facebook album you specified, and once the process is complete the publication of those photos will appear as a single timeline event.

Note that as the several photos are published, you will initially see an event for a single photo, but that will update as each photo is published so that you still only have a single timeline event for all of the photos you just published.