Category: Ask Tim Grey

Today’s Question: I know that posterization is bad, but I don’t know what it is! Can you explain what this term means?

Tim’s Quick Answer: Posterization refers to the loss of smooth gradations of tone and color in an image. As an example, a sky should generally appear as a very smooth gradation. If a photo that includes the sky becomes posterized, that sky will instead appear with obvious bands of color that don’t blend together very smoothly.

More Detail: More specifically, posterization refers to a situation where fewer color and tonal values are available to represent your image, creating “gaps” in the colors and tones that would normally fill in a gradation.

Under normal circumstances you are most likely to see posterization in an image that is in the 8-bit per channel mode, and when relatively strong adjustments are applied. Posterization is also much more likely to occur in black and white images, because a smaller number of overall pixel values are available when there are only shades of gray available.

Strong adjustments tend to reduce the total number of colors and tones available for an image. As an extreme example, consider a black and white image with an extreme increase in contrast applied to it. The most extreme version of a high-contrast black and white image would be one that only contains two tonal values: black and white, with no shades of gray in between. Higher contrast or saturation (among other adjustments) increases the risk of posterization.

To minimize the risk of posterization, I recommend always working with high-bit data if it is available. That generally means working with RAW captures, and converting those RAW captures as 16-bit per channel images rather than 8-bit per channel images.

As an example of the importance of bit depth, consider the number of tonal values available for a black and white image. In the 16-bit per channel mode you can have up to 65,536 shades of gray available for a black and white image. If that image is converted to the 8-bit per channel mode then only 256 shades of gray would be available, greatly increasing the risk of posterization.

Today’s Question: I realize there are tools for removing chromatic aberrations from a photo, but is there anything I can do to avoid chromatic aberrations in the first place?

Tim’s Quick Answer: Chromatic aberrations are caused primarily by issues with the lens being used to capture a given image. Therefore, the best way to avoid chromatic aberrations in your photos is to use lenses of the highest quality possible, and to favor lenses with longer focal lengths over wide-angle lenses.

More Detail: Of course, avoiding wide-angle lenses altogether isn’t really a great solution, since this approach can have a significant negative effect on the types of images you’re able to capture. So instead I recommend trying to ensure you are purchasing lenses of the highest quality possible. In the context of chromatic aberrations, this is of particular concern with wide-angle lenses.

Chromatic aberrations are caused by a variety of factors, but in general you can think of these colored halos along contrast edges as being caused by certain wavelengths of light being out of focus relative to the majority of wavelengths represented in the scene. Wide-angle lenses represent a particular challenge, since these lenses are “bending” the light from the scene more significantly in order to project that light onto the image sensor in the camera.

Higher quality lenses will do a better job of redirection the light from the scene, helping to reduce the risk of chromatic aberrations. In general you don’t need to worry as much about chromatic aberrations with lenses of relatively long focal lengths. But when it comes to wide-angle lenses, spending more for a higher quality lens can make a big difference in terms of overall image quality, including helping to reduce the risk of chromatic aberrations.

High contrast edges are the most likely areas to find chromatic aberrations, so avoiding such scenes would help you avoid chromatic aberrations. But again, I don’t think it makes sense to avoid photographing certain scenes or avoid using wide-angle lenses just to reduce the risk of chromatic aberrations in the first place.

Of course, as noted in the question, there are tools for removing chromatic aberrations in your photos, and they actually work quite well. That doesn’t mean that I would suggest purchasing a lens of inferior quality. But if a more expensive lens doesn’t make sense for you (and if you don’t want to stop photographing with wide-angle lenses), there are ways to significantly mitigate the appearance of chromatic aberrations in your images.

Today’s Question: Is there a way to transfer images from my iPad Air 2 directly to a thumb drive without using a computer? I own a desktop PC and do not have access to a laptop when traveling.

Tim’s Quick Answer: There are options, but they will generally require the purchase of special hardware. These include battery-powered hard drives with a WiFi connection, as well as specialty storage devices. You will need to use a special app on the iPad (or iPhone) to make use of these storage options.

More Detail: The best solution for you depends upon how much storage you need and your preferred workflow approach.

One option is to use a hard drive that supports a WiFi connection, using a special app to enable the transfer of files to or from that hard drive with a local WiFi network. An example of this type of hard drive is the Seagate Wireless Plus, available with storage capacity of 500GB, 1TB, or 2TB. You can get more details here:

http://timgrey.me/1SFln1v

Another option is to use a device that provides a WiFi connection to your iPad with a connector for a USB flash drive or storage card (such as an SD card). One example of this is the Kingston MobileLite device. With this type of device you would provide your own flash drive, for example, simply using the MobileLite as a way to connect that storage device to your iPad. This provides greater flexibility in terms of being able to make use of multiple flash drives, for example. You can see the Kingston MobileLite here:

http://timgrey.me/23JEkIi

Finally, you might consider a storage device that connects directly to your iPad or iPhone. One example is the SanDisk iXpand. This device contains two connectors along with the internal storage. The Lightning connector allows you to connect the device to your iPad or iPhone to transfer images (or other data), and the USB connector enables you to then transfer those files to your computer. Storage options range from 16GB to 128GB. You can find the SanDisk iXpand here:

http://timgrey.me/1p32OwC

It is worth noting, by the way, that these limitations regarding supplemental storage are primarily an issue with Apple devices such as the iPad and iPhone. With most Windows or Android devices you have much greater flexibility in terms of adding supplemental storage, including in many cases being able to simply connect a USB storage device.

Today’s Question: I used to use the crop tool to extend the canvas and fill with white or black as I needed. Lately, when I extend the canvas, I only see a transparent area, not a pixel area. I have to then create a layer under it and fill with white. Is there a setting that needs resetting?

Tim’s Quick Answer: When extending the overall dimensions of an image using the Canvas Size command, you will see transparent pixels in the new area if there is no Background image layer. Only if there is an actual Background image layer will the new pixels created by the Canvas Size command actually contain pixels rather than transparency.

More Detail: This is in some respects a matter of semantics, since transparent areas of an image will show up as white pixels in most contexts. However, you can ensure that the new area being added via the Canvas Size command contains “real” pixels by making sure you have a Background image layer.

To convert your primary image layer to a Background layer, you first need to select the applicable image layer on the Layers panel. You can do so by simply clicking on the thumbnail for that layer. Then go to the menu bar and choose Layer > New > Background from Layer. This will convert the current layer to a Background image layer, which in turn will cause the Canvas Size command to add pixels rather than transparency for the new area of the image.

It is worth noting that if you turn off the “Delete Cropped Pixels” checkbox on the Options bar when working with the Crop tool, the image you crop will no longer have a Background image layer once the crop is applied. In theory you might want to instead turn on the “Delete Cropped Pixels” checkbox to avoid this issue. However, it is important to keep in mind that having this option turned off can greatly increase your flexibility as you are fine-tuning the final effect for a given photo.

Today’s Question: You’ve said before that Lightroom’s Develop module and Adobe Camera Raw are the same in terms of image processing. So is there a way to use the same presets in both Camera Raw and Lightroom?

Tim’s Quick Answer: It is possible to use the same settings in Adobe Camera Raw and the Develop module in Lightroom. I recommend using a “test” image as the basis of creating a preset based on the same settings in both Lightroom and Adobe Camera Raw.

More Detail: There are other ways to “synchronize” your presets between Adobe Camera Raw and Lightroom, but I find the use of a “test” image to be the easiest.

The first step is to create the adjustment settings you want to use as the basis of your preset. Obviously if you have already created a preset there is no need to create it again. But if you have not yet created a preset for the settings you want to share across both applications, that is the first step. You can save this preset in either Adobe Camera Raw or Lightroom.

Once you have saved the preset so that it is available in one of the two applications, you can make use of a “test” image to create a preset based on the same settings in the other application. To create that “test” image from Lightroom, simply apply the applicable preset to the desired RAW capture, and then export that image to a folder on your computer using the “Original” option for File Format. This will export the RAW capture along with an XMP file that contains the Develop settings.

If you will use Adobe Camera Raw as the starting point, you can copy a RAW capture file to a test folder, and then use Adobe Camera Raw to process that image. Save a preset for the desired settings, and then click the Done button to close Adobe Camera Raw while saving the adjustment settings in an XMP file for the RAW file.

At this point you have saved the applicable settings for the image, so you are ready to use that image as the basis of creating a preset in the “other” application. If you started with Lightroom, you can just open the test image in Photoshop so it will be opened in Adobe Camera Raw. Then create a new preset within Adobe Camera Raw based on the current settings for the image.

If you started in Adobe Camera Raw, you can import your test image into your Lightroom catalog using the “Add” option during import. The settings you applied in Adobe Camera Raw will be applied automatically in the Develop module, so you can use those settings as the basis of a new preset in Lightroom. When you’re finished you can delete the “test” image, since it is presumably a copy of a photo that is already in your Lightroom catalog.

In both cases you are essentially creating a preset in one application, saving the settings for that preset to a test image, and then using the test image as the basis of a new preset in the other application. This may sound a little complicated, but it is actually rather straightforward and easy to accomplish.

Today’s Question: In Adobe Camera Raw under Lens Corrections and Remove Chromatic Aberration it’s limited to only 2 colors, purple and green. Nothing seems to work at all, no matter how I adjust the dials! What is going on here?!

Tim’s Quick Answer: If you’re not seeing an effect with the controls for removing chromatic aberrations, it is most likely an indication that you’re not using settings appropriate to the image you’re working on. I recommend increasing the Amount value for both purple and green to the maximum, and spreading the Hue control handles to the extreme ends of the scale. You should then see a rather significant loss of color along contrast edges in the photo, and you can then fine-tune the controls as needed for the photo.

More Detail: The controls you’re referring to are the Defringe controls, and they operate independently from the “Remove Chromatic Aberration” checkbox. In other words, you don’t need to turn on the “Remove Chromatic Aberration” checkbox in order to employ the Defringe controls.

In general I find that turning on the “Remove Chromatic Aberration” checkbox adequately resolves color fringing in about half of the photos that exhibit such fringing. For the other half of images that require this adjustment, the Amount and Hue sliders for purple and/or green must be used to produce a good result in the photo.

The Amount sliders (for purple and green) determine the degree to which the colors present in chromatic aberrations will be reduced in saturation. The two slider handles for the Hue sliders (for purple and green) determine the specific color range to be affected.

By maximizing the hue spread and the Amount setting for purple, you’ll be reducing saturation for colors ranging from cyan to red, including purple and magenta in between. In other words, colors within that range will turn gray.

Similarly, maximizing the hue range and the strength of the adjustment for the green sliders will cause colors ranging from orange through cyan (including green) to be reduced in saturation.

With this approach, you should see a relatively large gray area along contrast edges within the photo. Obviously you don’t want to actually remove so much color that you end up with a gray band along contrast edges in the photo. So you can then refine the settings as needed.

My general approach when it comes to using the sliders is to start with a high value for Amount, and then expand the Hue range until I can see gray fringing along contrast edges in the photo. I’ll then reduce the Hue range until only the problematic colors are being affected. I then reduce the value for Amount to establish a value that is just enough to remove the chromatic aberrations without causing new problems for the photo.

Today’s Question: Many of our friends prefer Adobe Bridge to Lightroom because the controls are easier to see (black on white) and also larger. The gray on black interface of Lightroom is harder to see and just doesn’t seem to communicate like Bridge. Or can those colors be changed?

Tim’s Quick Answer: Unfortunately you aren’t able to change the overall interface color in Lightroom in a way that will improve the readability of text and other controls. You can enlarge the font size, but you can’t change the colors for the text or controls.

More Detail: There is an option for changing the Background color in the Preferences for Lightroom. However, that option relates to the background behind the image, not to the overall interface.

You can change the Font Size option on the Interface tab in Preferences. There are options for “Small” and “Large”. I recommend the “Large” option to make the text easier to read. Note that when you change this setting you need to restart Lightroom for the change to take effect.

I agree that it would be very nice to be able to change the overall interface appearance within Lightroom. If you would like to let Adobe know you would like to see this update (or another feature or improvement) in a future version of Lightroom, I encourage you to submit the feature request form here:

http://www.adobe.com/products/wishform.html

Today’s Question: Can I search in Lightroom for images based on size or pixel dimensions?

Tim’s Quick Answer: Yes, you can search for images based on pixel dimensions in Lightroom, though not by the normal method of using filters. Instead you would need to create a Smart Collection for this purpose.

More Detail: Lightroom includes a variety of criteria to choose from when using the Library Filter to locate specific photos. However, pixel dimensions or other options related to the size of the image are not included. Smart Collections, however, can employ pixel dimensions as part of their criteria, providing a solution here.

Start by creating a new Smart Collection. To do so, click the plus (+) symbol to the right of the Collections header on the left panel in the Library module. Then choose “Create Smart Collection” from the popup menu to bring up the Create Smart Collection dialog.

You can define a variety of criteria as a filter for the Smart Collection, which will in effect become a saved search result that is updated automatically in real time. Enter a meaningful name for the Smart Collection, and then define your criteria below. In this case, for example, you could click the popup under the criteria listing and choose Size > Long Edge to define a size based on the longer side of the image.

The next popup allows you to specify how to evaluate the criteria. In this case, for example, perhaps you want to use the “is less than or equal to” option to find images with relatively short pixel dimensions. Enter the specific value in the text box to the right.

When you’re finished defining the criteria for the Smart Collection, click the Create button at the bottom-right of the Create Smart Collection dialog. You can then click on the name for this new Smart Collection in the Collections section of the left panel in the Library module to view all of the images that meet the specific criteria you defined.

Today’s Question: I am running out of disk space and would like to know the best way to archive photos that are part of my Lightroom catalog without loosing the ability to restore them if needed.

Tim’s Quick Answer: There are a couple of options you might consider. First, you could simply move some of your photos to a different storage location, without removing them from your Lightroom catalog. Second, you could export some of your photos to a separate catalog, and then remove them from your master catalog.

More Detail: My personal preference in this situation would be to obtain a larger hard drive and then transition all photos to that new hard drive. This approach enables you to retain all of your photos within your Lightroom catalog, with the ability to gain access to greater storage capacity.

If you don’t want to transition to a larger hard drive, you could certainly archive a portion of your catalog to a different drive. The first approach would be to simply move some of your folders to a different drive, doing so within Lightroom.

For example, you could create an archival storage location on a different drive. Start by clicking the plus (+) icon to the right of the Folders header on the left panel in the Library module in Lightroom, choosing Add Folder from the popup menu that appears. Navigate to a location that has adequate storage, and click the New Folder button. Create a new folder named something like “PHOTO ARCHIVE” and click the Choose button to add that folder to Lightroom.

Make sure you have a good backup of your photos before actually moving images. You could then drag individual folders from the existing storage location to the new “PHOTO ARCHIVE” folder you created on a different storage device. This will free up space on your primary storage device, while still enabling you to access those photos within your Lightroom catalog.

If you prefer to move the photos and remove them from your Lightroom catalog, I recommend creating a new “archive” catalog. You can select all of the photos you want to archive, and then use a two-step process to copy them to another catalog and remove them from the current catalog.

The first step here would be to use the Export as Catalog command found on the File menu to create a new catalog with the selected images. Be sure to turn on the “Export negative files” checkbox so that the actual image files are copied as part of this process. Once you’ve confirmed the photos have been copied successfully and that you have a full backup of all of your photos, you can use the Photo > Remove Photo command to remove the selected photos from your Lightroom catalog, using the option to delete the photos from the disk as part of that process.

It is important to use caution with either of these approaches in order to safeguard your images and avoid problems in your catalog.

Today’s Question: How would using ZIP compression rather than “None” [in the External Editing settings for Preferences in Lightroom] affect opening the resulting photo once it is sent back to Lightroom or Photoshop?

Tim’s Quick Answer: TIFF image files with ZIP compression are supported by a variety of software applications, including Photoshop and Lightroom. As a result, there is not a significant issue with using the ZIP compression option for images you are managing in a workflow that includes Lightroom and Photoshop. The only potential issue would be the risk of other software applications not supporting TIFF images with ZIP compression. In general you won’t find this to be a problem.

More Detail: In the External Editing section of the Preferences dialog in Lightroom you can specify the file type and other settings to be used when sending a photo to another application, such as Photoshop or various plug-ins.

In the past there had been issues with a lack of support for TIFF images with compression applied, especially with the LZW compression option. These issues have largely been resolved, with most imaging applications supporting both ZIP and LZW compression for TIFF images.

As a result, I generally don’t hesitate to apply compression to TIFF images. I typically employ the LZW option rather than ZIP, but both of these options provide lossless compression and are widely supported. In other words, either option will typically be perfectly fine, and will result in smaller file sizes compared to the “None” option.

Frankly, the bigger issue here relates to the potential to create layered images in Photoshop. When you create layers in Photoshop the resulting image cannot be opened with layers intact using other software applications, because the features in question are specific to Photoshop. But again, in the context of a workflow employing Lightroom and Photoshop, this isn’t a significant concern.