File Size Parameters

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Today’s Question: Is there is a difference in quality of image appearing in Flickr exporting from LR and uploading to Flickr using these two different methods:

1) Set file size specifically to 2.3MB

2) Set long dimension to 1920 pixels

I uploaded the same image using the two methods and Flickr shows the uploaded file size as:

1) Exported from Lightroom as a 2.3 megapixel file, then uploaded to Flickr. The image in the Flickr site has the original file size as 1856 x 1239 and 1.0MB.

2) Exported from Lightroom with longest dimension at 1920 pixels, then uploaded to Flickr.   The Flickr site has the original file size as 1920 x 1281 and  1.06MB.

Tim’s Quick Answer: There is no difference in terms of the image quality with either approach, assuming that you use settings that result in the same pixel dimensions with the same JPEG Quality setting.

More Detail: The Image Sizing section of the Export dialog in Lightroom provides a variety of ways you can describe the pixel dimensions you’re looking for. All of them essentially vary only in how you describe the final size of the image, not what the final size will be.

For simplicity, let’s assume an example where we’re exporting a square image, and that we want to create a file at a specific size. For our purposes we’ll assume we are exporting the photo to be printed at 10-by-10 inches at 300 pixels per inch.

In this case you can specify, for example, that you want the exported image to be sized at 10-inches by 10-inches at 300 pixels per inch (using the Width & Height option). You could also specify that you want the image to be 3,000 pixels on the long side (using the Long Edge option). You could use the Dimensions option and specify 3,000 pixels for both width and height, with the resolution set to 300 pixels per inch. And you could use the Megapixels option and specify 9 megapixels at 300 pixels per inch.

All of the above options are simply a different way to instruct Lightroom that you want the image sized to 3,000 pixels by 3,000 pixels. The various options are mostly provided simply because different people think of output sizes in different ways. They also provide flexibility in terms of being able to specify all images will be sized to the same size on the long edge regardless of whether the image is a horizontal or a vertical, for example.

The only “catch” with specifying the output size in megapixels is that you aren’t able to specify the pixel dimensions with as much precision, so to speak. This is illustrated by the example provided in today’s question.

If you multiple the pixel dimensions together for the example created with a 2.3 megapixel setting (1856×1239) you find that there are 2,299,584 pixels, which equates to 2.3 megapixels. The image sized based on the Long Edge option has pixel dimensions of 1920×1281, which translates to 2,459,520 pixels, or almost 2.5 megapixels.

So, if you had used the same pixel dimensions for the Long Edge option (1856 pixels) you would have ended up with two images of the exact same pixel dimensions, at the exact same image quality, and with the exact same file size.

Again, the resizing is performed based on the actual pixel dimensions, and there are various ways to describe those dimensions when exporting a photo. But with equal settings, all of the various options will produce the same result in terms of image quality.

RAW File Sizes

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Today’s Question: I recently bought a Fuji X-T1 camera. It has a 16 megapixel sensor. The file size in RAW (RAF) is approximately 33.3 MB. My Nikon D4 which also has a 16 megapixel sensor has a RAW file (NEF) of about 20 MB. When I convert the RAF file to a DNG, the file size goes down to about 21 MB (from 33MB). What’s going on here?

Tim’s Quick Answer: The size of a RAW capture certainly has a relation to the resolution of the image sensor, but it is also affected by the bit depth of the analog-to-digital conversion for the camera, compression applied to the RAW capture data, and other factors. In short, the sizes here are not unusual considering the amount of information being gathered.

More Detail: An image that contains around 16 megapixels of information (as is the case with the two cameras referenced in today’s question) will result in a file size (without compression) of about 92 megabytes if the image is saved in the 16-bit per channel mode. If the image is instead saved in the 8-bit per channel mode, that value will be cut in half to about 46 megabytes.

In other words, any file size for the RAW capture file that is less than the 16-bit uncompressed value for the image based on pixel dimensions is not too surprising. The bit depth of the analog-to-digital conversion plays a role, compression (even if lossless) plays a role, and “special” proprietary data saved by the camera will also affect the RAW file size.

In the specific example cited here, the information related to the NEF file size suggests that the captures are being processed at a lower bit depth, are being captured at a lower resolution, or have compression applied (all of these options are available for the Nikon D4). Based on the specifics here, I suspect you have compression enabled for the RAW captures on the Nikon D4. If you capture at full resolution and the full 14-bit per channel depth without compression, you can expect file sizes for the NEF capture that are about the same as those with the Fuji camera of the same resolution.

Converting a RAW capture to a DNG file will generally produce a file that is around 20% smaller than the original RAW capture, and so your experience with the RAF files does not stand out as being unusual. When you convert to DNG lossless compression is applied, which will reduce the file size compared to the original capture. The specific degree to which file sizes are reduced varies based on the original capture data.

So, you’re capturing the same amount of information, more or less, but producing files of a different size based on how that information is actually recorded. In general this relates to overall resolution, bit-depth, and compression, though in this case I suspect compression is the only real factor involved.

Print Specifications

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Today’s Question: [As a follow-up to yesterday’s question about preparing images to be printed by a lab], all of the labs I have come across instruct us not to use the profile for anything other than soft proofing. Most of them seem to want the print file in sRGB. Can you clarify? Also, most of the labs seem to want JPEG images, which doesn’t seem to make any sense. Why would they prefer JPEG?

Tim’s Quick Answer: I have a feeling that the reason many print labs prefer a “generic” working space profile rather than a specific profile is because many photographers don’t convert the images properly, creating difficulty for the printer. And I suspect the request for JPEG images is because the print lab is prioritizing small files that can be transmitted online more easily over final print quality.

More Detail: A profile for the specific printer, ink, and paper combination being used to print an image defines the specific range of colors (the color gamut) for that print condition. As such, that profile is the optimal profile to use not only for soft proofing the image but also as the actual embedded profile saved with the image.

In other words, if the printer has an ICC profile for the intended output conditions, it is indeed best to convert photos to that profile before sending the file to the printer. If there is a chance that a different paper or set of inks will be used to print the image, then it could certainly be advantageous to keep the image in a working space profile rather than a specific printer profile. But in general the specific printer profile is the best option.

As noted above, however, I suspect part of the reason that many print labs instruct photographers to use a working space profile rather than a specific profile is that photographers might be less familiar with the use of custom profiles, leading to images that haven’t been prepared correctly and therefore might not print as well as they should.

As for the request for JPEG (rather than TIFF) images, I am sure this is simply a matter of wanting a smaller file that can be easily transmitted through an online service, via FTP, or possibly even via email. However, you are sacrificing a degree of print quality when a JPEG rather than TIFF image is used as the basis of a print.

To be sure, it is possible to produce very good prints from a JPEG image. In fact, many magazine covers are printed from a JPEG image. But there is a risk of visible compression artifacts in the final print if the source image is a JPEG rather than a TIFF (or some other format saved with lossless compression or no compression at all). When you save a JPEG image, even at the highest quality setting, there is always some degree of lossy compression applied, and therefore some risk of visible compression artifacts in the image.

The specific risk when printing from a JPEG image depends upon the content of the image, the size at which the image is printed, and the quality setting used for the JPEG image. However, my preference would be to avoid these risks altogether and save in a format (such as TIFF) without lossy compression being applied.

Print Preparation

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Today’s Question: I am about to enter a competition at a gallery and need to print out my photos. I have calibrated my monitor with Colormunkie. I do not have a professional printer as of yet and need to send out my images to an outside printer.

Questions:

1) I have downloaded the paper/printer profile to my computer hard drive from the printer but do not know how to add this to the file using Lightroom.

2) Should I send the image as a TIFF or a JPEG? The printer accepts both. Don’t I lose some image information if I convert to a JPEG?

Tim’s Quick Answer: You can convert the image to a specific profile using the Color Space option in the File Settings section of the Export dialog. And I certainly recommend using the TIFF file format rather than JPEG, as some quality will be lost if you choose the JPEG format.

More Detail: Before you can actually use the profile for the images you export from Lightroom you need to copy that profile to the Profiles folder on your computer. On Macintosh you can copy the profile to the Library > ColorSync > Profiles folder on your startup disk. On Windows you can simply right-click the profile and choose Install Profile from the popup menu. With the profile installed you can proceed with the export process in Lightroom.

When you export an image from Lightroom you can choose a specific profile to use for the resulting image file. To get started, select the image you want to export and click the Export button at the bottom of the left panel in the Library module. This will bring up the Export dialog, where you can specify the various settings for the image file that will be created upon export.

In the File Settings section of the Export dialog you can set the Image Format option to TIFF. I recommend leaving the Compression option set to None (rather than ZIP) unless you have confirmed with the printer that they are using software (such as Photoshop) that supports ZIP compression for TIFF images.

To actually set the profile for the image, first click the Color Space popup, and then choose Other from the popup. Turn on the checkbox for the applicable profile, and click OK in the Choose Profiles dialog. The profile will then be available (and selected) on the Color Space popup.

You can then set the other options for the export, such as setting the output size for the image in the Image Sizing section. Depending on the specific print process being used, you will probably want to use a resolution of between about 300 and 400 pixels per inch at the specific output size for the print.

All of the other settings can be established based on your preferences (or based on instructions from the printer). Once you’ve finalized the settings, if you anticipate needing to export other images with the same settings you may want to save a preset. To do so, click the Add button at the bottom of the list of presets on the left side of the Export dialog, enter a name for the preset, and click Create.

With all of the settings established for the image (including the location where you want the image saved with the settings in the Export Location section at the top of the dialog) you can click the Export button in the Export dialog, and the selected image will be processed based on the settings you’ve established.

Black and White Workflow

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Today’s Question: Say I have an original colour RAW file that I really like but also know it will look good in black and white. So I want to make a virtual copy in Lightroom. Do I then make the adjustments I want in Lightroom to the colour file and then sync those changes to the black and white virtual copy as a starting point? Or would it be best to approach the straight black and white virtual copy with a fresh adjustment palette, as I would undoubtedly be looking for a different feel to the black and white version?

Tim’s Quick Answer: When you create a virtual copy in Lightroom, the adjustments already applied to the master image will also be applied to the new virtual copy. I recommend applying any corrective adjustments (such as noise reduction, chromatic aberration removal, blemish cleanup, etc.) to the original image before creating the virtual copy. You might also prefer to apply overall tonal and color adjustments, but it is important to keep in mind that these adjustments may need to be fine-tuned in the black and white version of the photo.

More Detail: When you convert a color image to black and white, there will be some changes in the overall appearance beyond the obvious loss of color information. Specifically, you may find that overall exposure and contrast need to be refined after converting a photo to black and white. This is due to the differences between color information based on individual channels and the underlying luminance information in the image.

If you won’t be presenting a color version of the image at all, then there’s no significant benefit to applying adjustments to the color image, or to creating a virtual copy in the first place. If you only want a black and white version of the photo, you could simply apply your adjustments directly to the original capture in Lightroom.

However, if you prefer to have both a color and a black and white version of the photo, then a virtual copy is called for. As stated above, my recommendation is to apply corrective adjustments first, so you don’t need to duplicate those adjustments for both the original image and the virtual copy.

Perhaps most important, however, is that you be sure to revisit all of the tonal adjustments for the black and white version of the image, as those adjustments are very likely to differ from those that were applied to the color image. I prefer to adjust the luminance values for each individual color in the B&W section of the right panel in the Develop module as a first step in working with the black and white version of the image.

However, I will then revisit the tonal adjustments in the Basic section to optimize the overall appearance of the image. I will also, of course, review all of the other various adjustment options as I finalize my black and white interpretation of the photo.

Capturing Vivid Color

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Today’s Question: Recently the color of the moonrise has been spectacular. The moon has been full and a deep orange/red color. The sunrise has had a similar color. However, I cannot capture the color in my photos. The moon is almost white and the sun is a boring orange/yellow. I have tried a variety of setting and had no luck capturing the color I am seeing.

Is there a trick to capturing these vivid colors?

Tim’s Quick Answer: I would say there are two “tricks” to getting great color in the sun or moon. First, a custom white balance setting can be very helpful. Second, keeping the exposure slightly dark can help preserve and accentuate the color.

More Detail: In my experience, when photographers struggle with accurate color photographing the sun or moon, exposure is the key problem. Specifically, I’ve observed a tendency to over-expose the image, which results in lost detail (blown out highlights) for one or more of the individual color channels.

To be sure, including the sun or moon in the frame can be a challenge, because both of these celestial objects are very bright (the moon during daylight hours is obviously not a challenge in this way). You may need to compromise on the exposure to preserve detail in the scene without giving up too much detail for the sun or moon. You could also use high dynamic range techniques to overcome this issue.

By keeping the exposure a little dark, you’ll both preserve detail in the bright areas of the photo, which will help preserve color in those areas. You will also darken the color values, which will actually create greater perceived saturation. So a slightly dark exposure can actually provide a considerable benefit when it comes to retaining the vivid colors when photographing a sunset or the moon at night.

When it comes to adjusting the color temperature setting, it is important to keep in mind that the camera is generally attempting to neutralize the color of the light illuminating a scene. That can result in an image where the vivid colors appear somewhat muted because they have been shifted toward a more neutral value.

The issue of color temperature can be resolved when processing your original RAW captures, so this is less critical to deal with in the original capture if you are shooting in RAW. However, it can be helpful to set a more accurate (or pleasing) color temperature setting even with RAW capture. I generally prefer to use the option to establish a specific Kelvin setting on the camera, using the Live View display to preview the color and adjusting the setting to one that produces the most accurate color for the scene.

I find that taking these issues into account when establishing settings for the exposure can have a dramatic impact on photographs that include the sun or moon.

Creating Pixels

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Today’s Question: How can Lightroom export at higher than the native resolution of the file? I thought Lightroom never created pixels but apparently it can. I tested it and sure enough, a capture from my camera at 5472 pixels on the long side was successfully exported to JPEG with 6000 pixels on the long side. Who made those extra pixels and is this as good as upsizing in Photoshop?

Tim’s Quick Answer: While Lightroom does not enable you to, for example, create composite images, that isn’t the same as saying that Lightroom can’t create pixels. Lightroom can indeed create pixels, including the ability to resample an image upon export so that the exported image contains a smaller or larger number of pixels than the original capture. The quality of this resampling in Lightroom is comparable to Photoshop.

More Detail: Lightroom is non-destructive, so when you are working in the Develop module you aren’t actually replacing the pixels in your original capture. Even things that might appear destructive at first glance, such as replacing pixels to clean up blemishes, are actually non-destructive. However, I think it is fair to say that Lightroom is creating pixels (perhaps in an indirect way) when you perform this type of work.

But when Lightroom is really creating pixels is when you export a photo. That is when your original capture is processed based on the adjustments you’ve applied in the Develop module to create a new image file. So, for example, you might use Lightroom to create pixels in the form of a JPEG image based on your original RAW capture.

When exporting a photo, you also have the option to change the pixel dimensions of the photo. Based on the typical display resolution for computer monitors, when presenting an image online (such as on a website) you don’t need much more than perhaps around 500 pixels or so of width for the image. Viewed at the actual pixel dimension size, an original capture that was over 5,000 pixels wide would be too big for a web page.

Similarly, if you are exporting an image so it can be printed, you might want to produce a larger file to create a larger print. For example, if you want to prepare an image to be printed 20 inches wide at 300 pixels per inch, you need 6,000 pixels across for the photo. If the original capture is “only” 5,000 pixels wide, the image would need to be resized to produce the desired print size.

Whenever an image file is created with pixel dimensions that differ from the dimensions of the original capture, pixels must be added or removed to produce the final pixel dimensions for the new image. This is a somewhat complicated process that involves calculations to ensure that color and tonal fidelity, fine detail, and overall sharpness, for example, are retained. Lightroom (and other applications) do a generally good job with this resampling work.

So yes, Lightroom is most certainly able to create (or destroy) pixels in the context of a derivative image being created through the Export facility, by virtue of being able to resize the image being exported to specific pixel dimensions based on your specific needs for the photo.

Image Preview Quality

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Today’s Question: Is viewing a file at 1:1 in Lightroom the same as viewing the same file at 100% in Photoshop? I have read, and heard, others say that most images don’t look sharp at 1:1 and should be viewed at 1:2 in Lightroom.

Tim’s Quick Answer: The “1:1” zoom setting in Lightroom is a 100% view, with each pixel in the image being represented by a single pixel on your monitor display. Just as in Photoshop, the 100% zoom setting is best for evaluating sharpness, though you may want to zoom in further to evaluate fine details (such as when checking for noise). It is important to keep in mind, however, that the most accurate preview for an image will be seen in the Develop module, not the other modules.

More Detail: The previews in Lightroom’s Develop module are created differently compared to the previews shown in the other modules, such as the Library module. In the Develop module the preview is based on a full rendering of the original image, while in the Library module the previews are based on JPEG renderings of your images.

At a 100% zoom setting the differences will be very subtle, but you can see some variations with close examination of the image when switching between the Develop and Library modules.

So, the Develop module should be used for all critical image evaluation. When evaluating sharpness, you should view the image with the 1:1 setting (100% zoom) so you are getting an “actual pixels” view, where one pixel in the image is represented by one pixel on the monitor display.

For evaluating noise and other fine details where you want to be able to see those small details better and aren’t as concerned about visible sharpness, I recommend using the 4:1 (400%) or higher zoom setting. And for evaluating the overall composition and framing, of course, I recommend zooming out to the Fit option, so you can see the entire image.

View Sizes

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Today’s Question: When I resize and resample to enlarge a print in Photoshop and want to check the pixels to see how the image might look printed I get confused. When I look at it “print size” it doesn’t appear nearly as large as the intended print. However if it looks good using this selection, does that mean it will look this good when printed? And what is 100 percent zoom for?  I feel unsure how to use these two options.

Tim’s Quick Answer: The Print Size view option is intended to provide a sense of how large the current image will appear when printed, not for evaluating image quality. To evaluate sharpness and other details related to overall image quality, the 100% (“actual pixels”) view option is best, as it ensures that each pixel in the image is represented by a single pixel on your monitor display.

More Detail: It is important to keep in mind that the Print Size option will not produce an accurate indication of the actual print size for most users, based on the default settings in Photoshop. Fortunately, you can resolve this issue so the Print Size preview actually reflects the print size for the current image.

First, you need to determine the pixel per inch resolution of your display. First, determine the actual pixel dimensions of the display within the settings for your operating system. Then measure the actual width of the display. Divide the number of pixels across by the width of the display. For example, my MacBook Air is set to a resolution of 1440×800 pixels, and the width of the display is 11.25 inches. Therefore, the pixel per inch resolution for this display is 128 pixels per inch (ppi). Note that the resolution of most displays, contrary to popular belief, is not 72 (or 96) ppi.

To adjust the display resolution setting in Photoshop go to the Edit menu on Windows or the Photoshop menu on Macintosh, and then choose Preferences > Units & Rulers. In the New Document Preset Resolutions section at the top-right of the Preferences dialog enter the resolution value you calculated into the Screen Resolution field, making sure that the popup is set to the correct unit of measure. Click OK to close the Preferences dialog.

With the actual pixel per inch resolution for your display established in the Preferences dialog in Photoshop, when you set the view option to Print Size the image will appear at the actual size that it will be printed. Keep in mind, of course, that the print size is based on the current output resolution and dimensions for the photo, which can be found in the Image Size dialog (Image > Image Size from the menu).

As stated above, the Print Size view option should be used for getting a sense of the output size, not for evaluating image quality. Instead, evaluating for sharpness and other factors related to image quality should be done at a zoom setting of 100%. At a 100% zoom setting one pixel in the image is represented by a single pixel on the display, so you are getting an accurate view of the information contained within the photo.

You can switch to the 100% zoom setting by choosing View > 100% from the menu (this option was called “Actual Pixels” in earlier versions of Photoshop). You can also establish a 100% zoom setting by double-clicking on the button for the Zoom tool on the toolbox, or by pressing Ctrl+Alt+0 on Windows or Command+Option+0 on Macintosh. Note that the last character of this keyboard shortcut is the number zero, not the letter “O”.

Camera Bit Depth

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Today’s Question: I just learned that my camera is actually capturing in 14-bits per channel when I shoot RAW, while I’ve been working in 16-bits in Photoshop. How much detail am I missing because my camera doesn’t support 16-bits?

Tim’s Quick Answer: Most digital cameras do perform the conversion of analog information (light) to digital information (pixel values) at a bit depth of 14-bits per channel. While most software provides a 16-bit per channel mode as the “high bit” option, the difference isn’t something you really need to be too concerned with.

More Detail: With most imaging software you have the option to work in either the 8-bit per channel mode or the 16-bit per channel mode. The primary advantage of a higher bit depth is that you have a wider range of tonal and color values available for the images. This is especially important with images that require relatively strong adjustments. The greater bit depth provides more overhead so that even with strong adjustments to the image there will be enough information “left over” to ensure smooth gradations of tone and color in the image. In other words, you’ll avoid posterization.

While the high bit depth option is generally a 16-bit per channel option, you can think of this as simply being a container that allows for more than 8-bit per channel information. Some cameras convert data at 12-bits per channel, most convert the data at 14-bits per channel, and a few actually process the data at a full 16-bits per channel. However, the differences aren’t as critical as they might seem.

The 8-bit per channel mode provides 256 tonal values per channel, which translates to almost 16.8 million possible color values. It so happens that this is the number of color values that the human visual system is estimated to be able to perceive, for someone with normal vision. So it would be fair to say that for the final image, 8-bits per channel is all you really need.

However, again, a higher bit depth can be very helpful, especially when strong adjustments will be applied to the image. By starting with more color and tonal values than you actually need, you’ll still have enough color and tonal values in the image even after adjustments have been applied, so that smooth gradations of tone and color will be preserved.

For a typical image with typical adjustments, however, that doesn’t mean you actually need the full range of color values provided by a bit depth of 16 bits per channel.

At a bit depth of 16-bits per channel you have 65,536 shades of gray available per channel, for a total of over 281 trillion possible color values. That is far more color and tonal values than you ever truly need in a photographic image, considering the capabilities of human vision.

At 14-bits per channel there are still 16,384 shades of gray per channel, for a total of over 4 trillion possible color values. And even at “only” 12-bits per channel there are 4,096 shades of gray per channel, for a total of over 68 billion possible color values.

So, the bottom line is that while an analog-to-digital conversion performed at 16 bits per channel will provide more possible color and tonal values in the image, there is a diminishing return relative to the final presentation of the image. In other words, there’s no reason to have any concerns about the fact that your digital camera performs the analog-to-digital conversion at “only” 14-bits per channel.