Ask Tim Grey

Today’s Question: For photos where you do want to have the lines appear perfectly horizontal or vertical, how do you recommend achieving that result?

Tim’s Quick Answer: To achieve perfect alignment in an image, I recommend applying profile-based lens corrections as well leveraging the Guided option for the Upright controls. Both of these adjustments (and additional manual controls for fine-tuning) can be found in both Camera Raw and Lightroom Classic.

More Detail: Today’s question is a follow-up to an answer I shared last week, where I explained that it wasn’t always necessary to have lines in an image appear perfectly horizontal or vertical just because that seems like the right approach. However, when you do want to achieve this type of alignment, a couple of adjustments can prove tremendously helpful.

As a basic starting point for achieving good alignment for a photo I recommend enabling the profile-based corrections, which apply a correction based on the behavior of the specific lens used to capture the image. Just keep in mind that not all lenses are supported for this feature.

To apply profile-based lens corrections turn on the “Use profile corrections” checkbox on the Profile tab of the Optics section of the right panel in Camera Raw, or turn on the “Enable Profile Corrections” checkbox on the Profile tab of the Lens Corrections section of the right panel in the Develop module in Lightroom Classic. Then make sure the appropriate profile is selected from the Profile popup based on the lens used to capture the photo.

I then recommend using the Guided option for the Upright corrections found in the Geometry section in Camera Raw or the Transform section in Lightroom Classic. With the Guided option you can draw between two and four lines to define lines in the image that should be perfectly horizontal or vertical. For example, with a photo of a building you might draw a line across the top of the roof and along the foundation line at the bottom, and then along the left and right edges of the building. This will apply a correction so the lines you drew are perfectly horizontal or vertical, which in turn means perspective of the image will be corrected accordingly.

You can also use the sliders in the Geometry section of Camera Raw or the Transform section of Lightroom Classic to further refine the overall perspective correction for the image, such as to further ensure that lines within the image appear perfectly horizontal or vertical.

Today’s Question: Since the last Lightroom Classic update, when I export a photo in any format, the colors of the exported image don’t “pop” and look washed out/faded in comparison to my image as viewed before export. Any comments or help would be greatly appreciated.

Tim’s Quick Answer: I suspect the issue you’re describing is being caused by an incorrect color profile, and possibly by using viewing software that is not taking the color profile into account.

More Detail: When you export a photo from Lightroom Classic you can choose which color profile should be used for the image. The options can be found on the Color Space popup in the File Settings section of the Export dialog in Lightroom Classic. For images that will be displayed digitally, such as on a computer display or smartphone, I recommend using the sRGB color profile.

The sRGB color space is well-suited for digital displays because the profile was actually originally created to encompass the range of colors that a typical monitor display was capable of reproducing. If you use a larger color space such as Adobe RGB or ProPhoto RGB, because that color space is likely beyond the capabilities of the display the image is being viewed on, the colors in the image will appear much more muted and possibly inaccurate.

In addition, if you’re using software that doesn’t support color management or has that support turned off, the colors will not be interpreted correctly. For a digital display if the source image is in the sRGB color space and viewed with software that isn’t using color management, the colors will probably remain relatively accurate. However, if an image that is in the Adobe RGB or ProPhoto RGB color space is viewed with software that doesn’t support color management, the colors will likely appear quite muted and possibly somewhat inaccurate.

Today’s Question: With a subject that includes horizontal and vertical lines, such as a building, how important is it to get the final image to have lines that are perfectly horizontal and vertical, versus being a little askew due to perspective issues?

Tim’s Quick Answer: While accurate alignment in a photo can be important, I don’t think it is always necessary to completely correct perspective issues for all images. In some cases, having lines that are not aligned perfectly can actually add to the impact of a photo.

More Detail: One of my biggest pet peeves when it comes to evaluating a photo is seeing blemishes or other distractions in the photo. In some cases that distraction takes the form of improper alignment, such as when a horizon is crooked. A more extreme example of a lack of proper alignment is when straight lines within the image don’t appear straight, and perhaps aren’t perfectly horizontal or vertical.

However, in many cases a lack of proper alignment can actually be a good thing. For example, if you use a very wide fisheye lens that has perhaps an angle of view of around 180 degrees, straight lines within the scene are most certainly going to appear curved and distorted. But that distortion is a big part of what makes a photo captured with a fisheye lens so interesting and eye-catching.

I think the most important consideration when it comes to correcting for perspective and alignment issues in a photo is what looks right or most pleasing for an individual photo. I rarely correct an image so that all lines are perfectly horizontal or vertical, though in some cases I most certainly do.

To provide a very general guideline, if you have a photo where the key (or solitary) subject clearly stands out in the frame and looks like it should have perfect alignment, then it probably makes sense to ensure that all lines are perfectly horizontal or vertical.

For photos that have a relatively wide angle of view, and especially when the perspective effect makes the image more interesting, I might apply some slight corrections such as to ensure that the lines of a key subject in the center of the frame are perfectly vertical. But I most certainly won’t correct all images to remove all distortion or to ensure that all lines are perfectly horizontal or vertical.

Again, in my view the emphasis should be on what looks appropriate and pleasing for the individual image. If lines look like they should be perfectly horizontal or vertical, it is generally worth making sure they are aligned properly. But keep in mind that in many cases having lines that are somewhat askew or perhaps are slightly curved can very much enhance the look of an image.

Today’s Question: I’m a little confused. Many, if not most, professional photo labs request that you send them images in a JPEG format. If artifacts are an issue, why don’t they request images in a TIFF format?

Tim’s Quick Answer: In my view photo labs should not suggest using the JPEG file format for printing because of the risk of visible artifacts. They do so, I assume, because the JPEG format is widely supported and results in a small file size that is easy to transmit via the internet.

More Detail: In some ways you could say that photo labs request JPEG images because photo labs have always requested JPEG images, at least in the context of online submission of images. The JPEG format is very widely supported and yields smaller file sizes than other file formats. However, that smaller file size comes at a potential cost in terms of print quality. Therefore, for printing I suggest submitting images as a TIFF or PNG file.

To provide some context, I saved a 20-megapixel image as a TIFF file with ZIP (lossless) compression and the file size was 146MB. The same image saved as a PNG file with maximum (lossless) compression was 95MB in size. The same image saved as a JPEG image with maximum quality (but lossy compression) was only 12MB.

In my view the risk of visible artifacts is a very real concern whenever printing a photo, and especially when that print will be relatively large. I therefore strongly recommend not using JPEG files for photos that will be printed. With high-speed internet being relatively ubiquitous today, sending a file that is around 100MB rather than around 10MB is not a major inconvenience, and in my view well worth it when it comes to helping ensure optimal print quality.

If a printer only supports uploading images in the JPEG format, I suggest finding a different printer. For example, I have had very good results getting prints from Bay Photo (https://bayphoto.com), and they allow you to upload images in a wide variety of image formats, including TIFF.

Today’s Question: If pixel per inch (ppi) resolution doesn’t matter for the digital display of photos, wouldn’t saving at 300 ppi create a larger file than with 72 ppi?

Tim’s Quick Answer: No. The pixel per inch resolution setting for an image has absolutely no impact on the file size.

More Detail: The total number of pixels in the image combined with the file type and related settings determine the file size for an image. The ppi resolution is simply a metadata setting used for determining the output size of an image when it is printed.

As may have been made abundantly clear by the number of questions I’ve addressed recently related to resolution in general and ppi resolution in particular, clearly this is a topic that leads to confusion.

The pixel per inch resolution is simply a way to explain the overall pixel dimensions in an image in a way that is intended to be more clear. For example, I think most people would agree it is more meaningful to say that an image is 10-inches wide by 10-inches tall rather than that the image consists of 3,000 by 3,000 pixels. But in order to say that an image is 10-inches across, we would need to specify the pixel density, which is what the ppi resolution provides. So instead of saying the image is 3,000 by 3,000 pixels, we can say the image is 10-inches by 10-inches at 300 pixels per inch. Both are saying the exact same thing in terms of pixel dimensions, just using different terminology.

Changing the pixel per inch resolution for an image will not affect the file size, all other things being equal. For example, let’s assume an image that is 1,000 by 1,000 pixels, in the 8-bit per channel bit depth, saved as a TIFF file without compression. The file size will be about 3MB. If you change the ppi resolution to 300 ppi, the file size is still 3MB because it still contains the same number of pixels. If you change the ppi resolution to 1,000,000 ppi the fie size is still 3MB because it still contains the same number of pixels.

Just remember that the ppi resolution simply provides a way for you to translate a set number of pixels to a set number of inches on the printed page. The ppi number is just a metadata value, intended to provide helpful translation information but unfortunately leading to confusion for many photographers.

Today’s Question: You suggested not saving an image as a JPEG if it is intended for print, because of the risk of compression artifacts. But what exactly are compression artifacts and what would they look like in the image or the print?

Tim’s Quick Answer: The compression artifacts for JPEG images appear as a grid pattern across the overall image, which is generally somewhat easy to spot if you use a high zoom setting especially on a JPEG image saved with a moderate quality setting.

More Detail: JPEG images use a compression method that is “lossy” meaning that actual pixel values are altered in order to reduce the file size. By contrast, images saved with a lossless compression method will preserve all pixel values precisely, while still reducing the file size. The advantage of lossy compression is that the file can be much smaller, but the disadvantage is the loss of image quality.

The way JPEG files compress image data is to break the image into blocks of pixels and then simplify the pixel data within each block. For example, that might mean a block of 8×8 pixels or 16×16 pixels. The pixel data within each of those blocks is compressed without evaluating the pixel values in neighboring blocks.

Because each block of pixels is compressed in isolation, the changes in one block won’t necessarily align well with the changed pixel values in a neighboring block. This can create an underlying grid pattern in the image that in some cases can be quite visible, both for images shared digitally and those that are printed.

The visibility of JPEG compression artifacts is greater when the image is saved at a relatively low quality setting. With some images, in fact, it may be very difficult to see the compression artifacts if the quality was set to a high value.

To get a better sense of what these JPEG artifacts look like, I recommend saving a copy of an image as a JPEG with the quality setting at the lowest value. For example, you can open an existing JPEG image in Photoshop, and then choose File > Save As from the menu. Specify a unique filename and storage location for this image, so you don’t confuse it with the original image. In the JPEG Options dialog set the Quality value to zero and click OK to save the image.

Next, open the image you just saved, and zoom in closely. You will see a very obvious grid pattern in the image. In fact, at such a low quality setting you may find that some blocks of pixels have been altered so that all pixels in the block (such as an 8×8 pixel block) have all been shifted to the exact same color.

Evaluating a JPEG image that has been saved at the lowest quality setting can help you get a better sense of what the JPEG compression artifacts look like. While these artifacts can be difficult to see on some images saved at a high quality setting, once you know what to look for you may still see artifacts in some areas of the image. Those artifacts, even if difficult to spot, can certainly translate to unwanted artifact patterns in the finished print, or for an image shared online.

Today’s Question: As a follow-up to your question about 16-bit versus 8-bit for derivative images created from a JPEG original, why not just use 8-bit per channel for all images that are sent to Photoshop rather than using a different setting for different images?

Tim’s Quick Answer: The primary reason to use the 16-bit per channel bit depth whenever possible for images that were captured at a high bit depth is to avoid posterization, which is the loss of smooth gradations of tone or color. This is of particular concern for black and white images or images that will require strong adjustments.

More Detail: One of the benefits of using raw capture with your digital camera is that you’re retaining the full capabilities of the image sensor, such as by maintaining high-bit data.

While we generally save our image files as either 8-bit or 16-bit per channel, cameras often capture images with bit depths in between these values. Many cameras capture at 10-bit or 12-bit for example, with top cameras supporting full 16-bit per channel bit depth.

The bit depth refers to the total number of possible tonal and color values in the image. A single bit is simply off or on, generally referred to as having a value of zero or one. With two possible values for each bit, you can use exponents to determine the total number of tonal and color values based on the bit depth.

For example, 8-bit per channel can be calculated as two raised to the power of eight, which equals 256. Since there are three channels in a color photograph, that means we can cube that value (256 to the power of three) to determine that an 8-bit per channel RGB image can contain up to 16,777,216 colors.

That is a relatively large number of color values, and in fact it is regarded as the approximate number of discrete color values that can be perceived by normal human vision. However, the picture is not so good when it comes to a black and white image. In that case the image would only support up to 256 shades of gray, which is not very many shades at all.

In addition, applying adjustments (especially strong adjustments) to an image can reduce the total number of tonal and color values represented by the image. The stronger the adjustments, the greater the risk that smooth gradations will no longer appear smooth.

Working in the 16-bit per channel bit depth provides much greater latitude for your images. For color images with 16-bit per channel data you will have up to more than 281 trillion possible color values. Even for black and white photos you would have up to 65,536 shades of gray available.

Even if you’re creating raw captures with a camera that only supports 10-bit or 12-bit analog-to-digital conversion, there are still potentially significant benefits to using the 16-bit per channel mode rather than downgrading to 8-bit per channel mode.

A 10-bit per channel capture can represent over 1 billion possible color values, or up to 1,024 shades of gray for a black and white image. A 12-bit per channel capture can represent over 68 billion possible color values, or up to 4,096 shades of gray.

I recommend keeping images in the 16-bit per channel mode unless the source image used to create a derivative image was captured in 8-bit per channel bit depth to begin with, as would be the case with a JPEG capture.

Today’s Question: If I send a JPEG to Photoshop from Lightroom Classic and want to create a copy rather than editing the original JPEG, I assume that I’m creating a 16-bit per channel image from the 8-bit per channel JPEG based on the External Editing settings in Preferences. If so, should I change that setting before sending a JPEG to Photoshop from Lightroom Classic?

Tim’s Quick Answer: My recommendation in this context is to keep the Preferences set to the 16-bit per channel option, but then convert the image to 8-bit per channel mode in Photoshop before saving the finished image.

More Detail: When you create a new file when sending a photo from Lightroom Classic to Photoshop, the new file is created based on the settings established on the External Editing tab of the Preferences dialog in Lightroom Classic. That means you’re either creating a Photoshop PSD or TIFF file, and that by default the new file will be set to a bit depth of 16-bits per channel (per component).

When you send a JPEG image with a bit depth of 8-bits per channel to Photoshop and the resulting PSD or TIFF file is set to a bit depth of 16-bits per channel, you’re creating a file that is twice as big as it needs to be, with no real benefit in terms of the quality of the derivative image you’re creating.

While it is possible to change the settings on the External Editing tab of Preferences before sending a JPEG image to Photoshop, I don’t recommend taking that approach. Put simply, you might change the setting before sending a JPEG image to Photoshop, and then forget to change the setting back to 16-bit per channel option before sending a raw capture to Photoshop. I therefore recommend keeping the setting at 16-bits per channel, which is the safest and preferred setting.

Instead, when you create an image in 16-bit per channel mode based on a source image that was only captured at 8-bits per channel, I recommend changing the bit depth for the derivative image in Photoshop before saving the final result. To do so, go to the menu in Photoshop and choose Image > Mode > 8 Bits/Channel.

This approach ensures that by default you’re creating derivative images when sending a photo from Lightroom Classic to Photoshop with a bit depth of 16-bits per channel, which provides greater latitude in terms of color and tonal values. You can then convert the derivative image to 8-bits per channel for images that were created based on an 8-bit per channel original. With this workflow, the worst thing that might happen is that you forget to convert an image created from a JPEG to the 8-bit per channel bit depth. That would just mean that the file was twice as large as it needed to be, but there’s no problem in terms of image quality. More to the point, taking this approach means you won’t inadvertently create a derivative image at 8-bits per channel for a source image that was 16-bits per channel.

Today’s Question: I can export my processed photos (from Capture One) as either JPEG or TIFF format, as well as DNG or PNG. Which format is preferable for printing?

Tim’s Quick Answer: When saving an image intended for print, I recommend saving as a TIFF file, because that will help ensure optimal quality for the finished image. I also recommend using the 16-bit per channel mode when exporting the TIFF image, assuming the source image was a raw capture or otherwise high-bit capture.

More Detail: The only format I strongly recommend against using when creating a derivative image for the purposes of printing a photo is the JPEG format. That’s because in almost all cases the JPEG format uses lossy compression, which means that even at a high setting for quality there will still be compression artifacts in the image. This can create a problematic pattern in the print, which can be avoided by using a different file format.

While not all printers support 16-bit per channel data output to the printer, I still recommend saving the derivative image as a 16-bit file to maximize the potential output quality. To be sure, as long as the image doesn’t need to be edited after creating the TIFF file, there is really very little benefit to saving this derivative image in the 16-bit per channel mode rather than 8-bit per channel mode. However, I prefer to err on the side of optimal print quality, and so recommend saving in the 16-bit per channel mode.

In addition, the TIFF file format is very widely supported by software and is recognized and supported by virtually all printing services. All things considered, in my view the TIFF file format is the best option to choose when saving a derivative image for printing.

Today’s Question: I have tagged many people in photos [with keywords in Lightroom Classic]. Now I want to search for certain people in the photos. I can find a single person, but I can’t seem to search for photos that contain multiple people. Is there a way to search for photos that contain two specific people?

Tim’s Quick Answer: You can search for photos that have keywords for two (or more) different people by using the Text search for the Library Filter Bar in Lightroom Classic, making use of the “Contains All” option.

More Detail: There are a variety of ways you can search for photos based on keywords in Lightroom Classic, including searching for keywords that represent the names of specific people who appear in a photo. In many cases when you specify multiple criteria for a search in Lightroom Classic, the search is conducted based on an “or” option. For example, if you search for keywords of “Paris” and “London”, the search result would include photos that have either Paris or London as keywords.

If you want to search for only those photos that include two (or more) keywords, such as to find photos keyworded as including more than one person, you can use the “Contains All” option for the Text tab of the Library Filter Bar.

To get started, navigate to the location (such as a folder, or even the All Photographs collection) that you want to search. Then go to the Library Filter bar above the grid view in the Library module. If the Library Filter Bar isn’t displayed, you can choose View > Show Filter Bar from the menu.

On the Text tab of the Library Filter Bar, select “Keywords” from the first popup to search based on keywords in metadata. From the second popup choose “Contains All”, which will cause the search result to only include photos that contain all the keywords you specify. In the text box to the right of the two popups you can then enter the applicable keywords (in this example the full keywords representing the names of the people), with the keywords separated by commas.

The result will be only photos that include all the keywords you entered into the text field, along with any other filter criteria you may have specified from the other tabs, such as to also filter based on star ratings.