Ask Tim Grey

Today’s Question: Do you have a preference for using the “increase/decrease” exposure control in the camera over changing the current ISO value that you are using? It seems (on my Nikon) that using this control is easier (faster) than selecting a different ISO number.

Tim’s Quick Answer: To me the most important consideration here is how you are impacting the final exposure settings. Ultimately, any technique that enables you to quickly achieve optimal settings for the overall lens aperture, shutter speed, and ISO settings is a good technique as far as I’m concerned. I would just caution against allowing one setting to become problematic just because changing a different setting was faster or easier. For example, I wouldn’t want to let the shutter speed get too slow just because it was easier to apply exposure compensation rather than change the ISO setting.

More Detail: I find that most photographers understand the basic concepts related to the “exposure triangle” of lens aperture, shutter speed, and ISO setting. However, I also find that many photographers get confused about when to adjust specific settings, including exposure compensation.

Exposure compensation enables you to apply an adjustment to the overall exposure settings when using an exposure mode other than Manual mode. For example, if you are photographing a snow-capped mountain, the camera’s meter may produce an exposure where the areas covered in snow are completely blown out. You could then apply a negative exposure compensation value to reduce the exposure and retain highlight details in the snow. For example, if you applied a one-stop exposure compensation value you might cause the shutter speed to go from 1/250th of a second to 1/500th of a second, creating a darker exposure.

The ISO setting enables you to have the camera apply amplification to the signal being captured by the image sensor. If you are in the Manual exposure mode, then increasing the ISO setting will indeed cause a brighter exposure, assuming you didn’t change the settings for the shutter speed and lens aperture.

However, in one of the automatic or semi-automatic exposure modes, changing the ISO setting will not change the overall exposure. For example, let’s assume you had the camera set to an aperture of f/8 and a shutter speed of 1/250th of a second at 100 ISO while in Aperture Priority mode. If you then increase the ISO setting to 200, the shutter speed would change to 1/500th of a second. You would have changed the shutter speed along with the ISO setting, but you would not have actually changed the overall brightness of the exposure.

Taking all of this into consideration, my recommendation is to find the best way to achieve optimal overall exposure settings with minimal compromise. In general, I find that involves prioritizing the most important exposure setting based on the circumstances, but reviewing all of the exposure settings to ensure you aren’t creating problems. For example, if you want lots of depth of field you might want to stop the lens down completely. However, that could result in a shutter speed that is too slow. And, of course, you also need to consider the effect of increased ISO settings on the noise levels within the photo.

There is much to consider when establishing the overall exposure settings, but with practice it does get easier to evaluate and decide on those settings more quickly. And again, any technique that enables you to achieve optimal settings quickly is a good technique as far as I’m concerned!

Today’s Question: Sometimes when I’m cropping a photo in Photoshop and I only need to bring the crop in a small amount from the edge, Photoshop won’t let me. When the crop edge is close to the edge of the photo, the crop sticks to the edge of the photo rather than the position I want it. Is there a way to stop this behavior?

Tim’s Quick Answer: There are two basic approaches you might consider, both of which are related. You can turn off the “Snap” feature altogether, or you can temporarily disable this feature while working by holding the Ctrl/Control key on the keyboard.

More Detail: The behavior you’re referring to is called “Snap”, meaning that the object you’re moving (in this case the edge of the crop box) will snap to the edge of the photo when you move close to that edge. This behavior can be helpful when you’re trying to precisely align the crop box along an edge in the photo, rather than just inside or outside the edge of the photo. But of course, this behavior can also be a challenge when it isn’t wanted.

If you hold the Ctrl key on Windows or the Control key on Macintosh, the Snap behavior will be temporarily toggled. Since the Snap option is turned by default, that means that holding the Ctrl/Control key will disable the Snap feature as long as you’re holding that key down. And yes, it really is the Control key (not the Command key) on Macintosh. This is one of the rare situations where the Ctrl key on Windows does not translate to the Command key on Macintosh.

If you find the Snap behavior distracting in general and prefer to turn it off altogether, you can do so by choosing View > Snap from the menu. This will disable the Snap feature in all cases within Photoshop. Note that you need to have an image open in order to access this menu item.

Note that you can also turn off only the “Document Bounds” option for the Snap feature, so that the Crop tool won’t snap to the edge of your photo. This allows you to keep the Snap feature active for other features, such as with Guides and Layers. You can find the various options for a selective Snap feature by choosing View > Snap To from the menu. On a sub-menu you will see the available options, with a checkmark icon indicating which specific options are enabled. You can click on any of those options to toggle them off or on as desired.

Today’s Question: I prefer to download my iPhone captures to a folder on my desktop first, and then import into Lightroom. Sometimes I accumulate several folders full of images that need to be imported. Is there an easy way to import all of those folders at once so I don’t have to import multiple times (once for each folder)?

Tim’s Quick Answer: There are several options available to you, but in this case the easiest approach might be to simply select the multiple folders from the Source panel in the Import dialog. This allows you to select multiple folders of images and import them to the same folder location using the Copy option.

More Detail: On the left side of the Import dialog you are able to select the source of images to be imported. In this case, for example, the source might be a folder on your desktop that contains photos. What many photographers don’t realize is that it is possible to select more than one folder from the Source panel, enabling you to import the photos contained in multiple folders all at the same time.

The approach to selecting multiple folders is the same that you might already be familiar with in your operating system. You can click on the first folder, for example, and then hold the Shift key and click on the last folder to select multiple folders. You can also hold the Ctrl key on Windows or the Command key on Macintosh while clicking in order to toggle the selection of a folder on or off.

In this case you could then use the Copy option at the top-center of the Import dialog to enable you to copy the photos in the multiple folders to the final destination, such as a folder for a current trip on an external hard drive.

You could also select the parent folder (such as the Desktop in this case) and turn on the “Include Subfolders” checkbox at the top of the Source panel. This will cause all photos in all subfolders of the currently selected folder to be included in the import, although you need to be careful to ensure that this approach doesn’t cause unwanted photos or videos to be imported.

You could even automate things further by creating a “watch” folder, so that whenever new images are added to a given folder they can be imported into Lightroom automatically. But again, in this specific example I think simply selecting multiple folders from the Source panel in the Import dialog may represent the best solution.

Today’s Question: How do you set Lightroom to apply automatic Lens Correction on Import?

Tim’s Quick Answer: There are two steps involved here. First, you need to create a preset in the Develop module for the adjustments you want to apply on import (such as Lens Corrections in this case). Then select that preset from the Develop Settings popup in the “Apply During Import” section of the right panel in the Import dialog.

More Detail: To create a preset in the Develop module you establish the applicable adjustment settings for an image, and then save those settings in a preset. In this case, if you want to apply an automatic Lens Corrections adjustment, you would simply establish the desired settings.

So, select an image and go to the Develop module. Then scroll down to the Lens Corrections section and go to the Profile tab. Turn on the “Enable Profile Corrections” checkbox, and set the Setup popup to “Auto”. You can also go to the Color tab and turn on the “Remove Chromatic Aberration” checkbox if you’d like. And, of course, you can add any other adjustments you’d like to apply during the Import process.

Once those adjustment settings are established, you can go to the left panel in the Develop module and click the plus symbol (+) to the right of the Presets heading. In the New Develop Preset dialog, first enter a meaningful name, such as “Add Lens Corrections”. Then click the “Check None” button so that none of the selection options are turned on. Then turn on the checkbox for only those adjustments you want to include with this preset. In this case, for example, you might only turn on the “Lens Profile Corrections” and “Chromatic Aberration” checkboxes. Then click the Create button to save the preset.

In the Import dialog when you next import photos, you can choose your new preset from the Develop Settings popup in the “Apply During Import” section of the right panel in the Import dialog. That setting will remain applied until you change it, so that all imported images will in this case receive the Lens Corrections adjustments.

Today’s Question: My camera of choice is a Canon 6D. I have the option of using sRGB or Adobe RGB [as the color space]. Which one should I use?

Tim’s Quick Answer: If you are using the RAW capture mode, either option is fine because this setting won’t actually affect the RAW capture data (more on why you might choose one over the other is included in “More Detail” below). If you’re shooting in JPEG, I would recommend considering capturing in RAW in stead. But if you need to shoot JPEG, I would generally recommend Adobe RGB (although there are situations where sRGB might make more sense).

More Detail: For RAW captures, the color space option you select in the camera doesn’t actually affect that RAW capture. That is because until the RAW capture is actually processed to create the full pixel values, the color space profile is not finalized. In other words, for a RAW capture you can change the color space when rendering a different file, such as a TIFF or JPEG image.

That said, there are reasons you might prefer one or the other of these options. In general, choosing sRGB in the camera will cause the preview image you see on the camera’s LCD display to be a little more saturated and possibly with a little more contrast. In other words, you’ll likely have a slightly more pleasing image preview.

If you choose the Adobe RGB option, the preview might not be quite as pleasing, but the histogram will also be a little more accurate. But the difference here will really be quite minimal, especially in the context of a RAW capture with greater flexibility in post-processing.

The bottom line is that either option is perfectly fine for RAW captures. For a JPEG capture, I would generally favor the Adobe RGB color space, because it is a larger color space. However, if your workflow involves the exclusive use of the sRGB color space (which is very common for wedding and portrait photographers, for example), then it certainly makes sense to employ sRGB in the camera as well. And, as noted, if you are capturing in JPEG, you might consider whether the RAW capture option might provide meaningful benefits to your workflow.

Today’s Question: In the past year I have started correcting for chromatic aberration and lens profile correction as part of my import preset in Lightroom. Is this a good idea to correct for aberration upon import to Lightroom for all images, or is there a potential downside to this approach? I understand that chromatic aberration correction is not needed for many images, but does it do any harm to select it for all images upon import?

Tim’s Quick Answer: In my opinion there is absolutely no reason not to apply an automatic Lens Correction adjustment during import, including the application of an automatic correction for chromatic aberration.

More Detail: To begin with, I have found the Lens Correction adjustments in Lightroom and Adobe Camera Raw to be beneficial, and without causing any image quality problems for the photo. In other words, I’m comfortable applying a Lens Correction adjustment to all images, even for images that don’t necessarily need any real adjustment in this regard.

Furthermore, there is no problem applying the automatic adjustment for chromatic aberrations, even for images that don’t necessarily need such an adjustment. I have not seen any degradation in image quality based on the application of a correction for chromatic aberrations for an image that does not actually exhibit any such aberrations.

So, I think it is perfectly reasonable (and even smart) to apply Lens Corrections adjustments for all images as part of the import process in Lightroom, or as a default adjustment in both Adobe Camera Raw and Lightroom.

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.