Stacking Depth of Field


Today’s Question: In response to a question about hyperfocal distance and depth of field, you said “…when it will be impossible to achieve the desired depth of field with a single capture.” How is it possible to achieve more depth of field with more than a single capture?

Tim’s Quick Answer: You can expand depth of field for a scene by essentially bracketing the focus with multiple captures set at different focal points. This is referred to as focus stacking, and it can be very effective at providing greater depth of field than you could otherwise achieve in a single exposure.

More Detail: In many cases it can be difficult (or impossible) to achieve as much depth of field as you’d like. An extreme example would be macro photography, where you are focusing so close to the subject that you will have depth of field measured in the fractions of an inch. However, even with landscape photography you can easily run into a situation where you’re not able to get as much depth of field as you’d like.

Focus stacking to achieve greater depth of field is similar in concept to creating an HDR image. The difference is that for HDR you bracket the exposures, while for focus stacking you bracket the focus point.

Some cameras actually include built-in focus stacking. During my recent Palouse Photo Workshop ( a couple of photographers were making use of this feature with a Nikon D850, and the results were quite impressive.

It is also possible to manually create focus-stacked images. You need to adjust the focus for each of a series of exposures, making sure that you overlap the depth of field for each exposure to cover the entire area you want in focus in the final image.

You can then use software to assemble the resulting photos into a final focus-stacked image. My personal preference is Helicon Focus (, which I’ve been using for focus stacking for quite a few years with excellent results. Another option is Zerene Stacker ( Both provide similar options for building a final image by blending the original captures to maximize depth of field.

And, of course, some photographers take an even more manual approach, capturing several images and then blending them through the use of layer masks in Photoshop.

Specifying Preview Type


Today’s Question: How can I specify that I want Standard Previews in Lightroom Classic CC?

Tim’s Quick Answer: There are two ways you can have Lightroom generate Standard previews (rather than 1:1 previews, for example). You can either select the Standard option from the Build Previews popup in the Import dialog at the time you import photos into Lightroom, or you can use a menu command to generate previews after import for selected photos.

More Detail: This question is a follow-up to a previous question that related to the use of the “Embedded & Sidecar” preview option. In short, I recommended using the Standard (or 1:1) preview option rather than the “Embedded & Sidecar” option.

You can specify the type of preview you want Lightroom to generate right at the time the images are being imported into your Lightroom catalog. From the Build Previews popup in the File Handling section of the right panel in the Import dialog, simply choose the desired option, such as “Standard” or “1:1”. As soon as the images have been imported, Lightroom will generate previews of all of the photos, storing those previews alongside the catalog file.

If you had been using a different preview option during some of your previous imports, or you otherwise need to re-generate previews for some images, you can most certainly perform that task at any time. Simply select the photos you want to generate previews for (such as all photos in a given folder) and then choose the desired preview option from the submenu at Library > Previews. For example, to generate Standard previews you could select Library > Previews > Build Standard-Sized Previews. Note that you do need to be in the Library module to be able to select this menu option.

Note that it is even possible to re-generate previews for all photos in your entire Lightroom catalog. To do so, you could first choose “All Photographs” from the Catalog section of the left panel in the Library module. Then choose Edit > Select All in order to select all photos in your catalog (making sure you don’t have any filters set first). Then choose the desired preview option from the Library > Previews submenu, and Lightroom will build updated previews as needed for all selected photos.

Focusing at Hyperfocal Distance


Today’s Question: Would focusing at the hyperfocal distance help in this case [of a photographer wanting to maximize depth of field for a scene]?

Tim’s Quick Answer: Yes, if your goal is to maximize depth of field for a scene, setting the focus for a lens to the hyperfocal distance will provide an optimal result, all other things being equal.

More Detail: In an Ask Tim Grey eNewsletter last week I addressed a question from a photographer who was trying to understand which lens aperture setting to use when focusing from a distance. The implication was that greater (or maximum) depth of field was desired.

The hyperfocal distance is the closest distance you can focus on while still retaining acceptable focus at infinity. In other words, all other things being equal, if you set the focus distance at the hyperfocal distance, you’ll have the maximum possible depth of field for the scene.

The key is to actually determine what the hyperfocal distance is for a given set of circumstances. This can be especially challenging since the hyperfocal distance will change based on changes in lens focal length or aperture setting.

In fact, the example scenario I defined in my previous answer on this subject was chosen as an illustration of focusing at hyperfocal distance. I had used the example of a 200mm lens on a given camera, with the lens aperture set to f/8 and a subject at a distance of about one-quarter mile. With these settings, it happens that the hyperfocal distance would be 497.3 yards, which is just over one-quarter of a mile.

If you are using a calculator (such as a smartphone app) to calculate depth of field, that calculator probably already provides an indication of the hyperfocal distance. Setting the lens focus at that point would yield maximum depth of field.

Of course, the bigger challenge in all of this is that with most lenses it is not very easy to set focus at a specific distance. That said, calculating the hyperfocal distance can be helpful in terms of providing a good sense of what is possible in terms of overall depth of field. For example, with a 100mm lens set to an aperture of f/22 but focusing on a subject three feet away from the lens, the hyperfocal distance would be about 135 feet.

In other words, it is impossible to achieve enough depth of field so that the subject close to the lens is in focus, while focus is also maintained at infinity. By calculating depth of field (and thereby obtaining hyperfocal distance) under a variety of circumstances, you’ll get a better sense of when you are able to achieve greater depth of field, and when it will be impossible to achieve the desired depth of field with a single capture.

Lower Noise with Higher ISO


Today’s Question: Regarding the base ISO setting, someone told me that for Canon cameras it was 160. True?

Tim’s Quick Answer: I would say that in the case of Canon cameras the base ISO is generally 100, but you may see less noise at 160 ISO compared to 100 ISO. The same concept would generally apply for higher ISO settings as well.

More Detail: My understanding is that many (or most) digital cameras only use hardware amplification for certain ISO settings. These are often in one-stop increments, so that hardware amplification is employed for 100 ISO, 200 ISO, 400 ISO, and so on.

For “in between” ISO settings, the nearest hardware amplification value would be used, and then the signal is processed after the capture to increase or decrease the effective amplification with software.

What that means is that a capture at an ISO setting of 160 is really a capture at 200 ISO with the resulting image darkened by one-third of a stop. The result is that while there may have been more noise in the initial capture, that noise was masked by the image having been darkened. By contrast, at an ISO setting of 125, the lower setting of 100 ISO would be used for the actual capture, but then the signal is amplified by one-third of a stop after the capture by software.

The key here is that in general software amplification is inferior to hardware amplification. This is why you might see more noise at 125 ISO than you would at 160 ISO or potentially even 200 ISO.

The specific results will vary from one camera to the next, based on a wide variety of factors related to base sensor sensitivity, the nature of the various types of hardware and software amplification applied to the signal, noise reduction applied to the resulting data, and more.

To be sure, you will often see that noise levels do not increase in a linear manner as you raise the ISO setting. Furthermore, you may see less noise at a higher ISO setting in some cases, as noted above. This is part of the reason I strongly recommend doing some testing on your own to get a better sense of the overall noise behavior for your camera. This is especially important if you tend to use very high ISO settings on a regular basis in your photography.

Potential Catalog Corruption


Today’s Question: I tried to open my Lightroom catalog and it said, basically, it was corrupted but to try again later. My hard drive would not release from the computer, repeatedly saying it was busy. I shut down the computer, and the next day I tried repair again and it worked. What happened and why did it work a day later?

Tim’s Quick Answer: While it is possible that this was simply a case of random file corruption, the specific circumstances cause me to worry that the hard drive (or other hardware component) may be the source of the issue. I would therefore want to immediately make a backup of all of your data, and to perform at least some basic testing to try to confirm there are no ongoing issues.

More Detail: File corruption in general can be quite frustrating, in part because there isn’t generally any warning that something has gone wrong until it is too late. I’ve seen many photographers (myself included) who had original raw captures appear as corrupted, long after the source files had worked perfectly fine.

While it is certainly possible for a software issue to lead to such file corruption, in my experience it is more often a hardware issue. It can be challenging to test the full chain of hardware devices involved in reading and writing data on a computer, but I would attempt to perform some testing to gain confidence in the overall setup.

For example, I would try writing files to and reading them from an external hard drive, swapping out the data cable, and also testing the same drive on a different computer. The idea is to change each variable individually as you try to determine where a problem exists.

You can also have a computer repair shop perform some tests on the various hardware involved, in an effort to confirm whether there are problems with any of the hardware you’re using.

At the very least, however, I would immediately make a full backup of all data, ideally to more than one backup drive. As I’ve noted in previous Ask Tim Grey email newsletters, I also highly recommend using the built-in backup feature to backup the Lightroom catalog. In particular, this backup provides you with the option to test the integrity of the catalog files as well to perform optimization of the catalog. Both of these steps can help avoid problems and improve performance with Lightroom.

Noise Testing


Today’s Question: In a recent email you suggested doing some testing in order to get a sense of the impact of ISO on noise levels for a given camera. How do you recommend doing that testing?

Tim’s Quick Answer: I recommend capturing a series of test exposures that enable you to see the impact of various camera settings on the noise levels in your photos. The key is to create a series of simple captures, focusing on changes to on variable at a time (to the extent possible).

More Detail: There are a number of variables that affect noise levels in digital captures, but one of the most significant is generally the ISO setting. This will therefore typically be the key variable to focus on, but you’ll want to consider other factors as well.

To begin with, I would generally use a subject with a solid color and minimal texture, such as a gray card. A blank backdrop or other simple surface can be used as well. Then, with the camera on a tripod, configure the camera for a normal exposure. I would typically use Aperture Priority mode with the lens aperture wide open, to ensure the fastest possible shutter speeds. This will help ensure that the impact of a long exposure is not affecting your test results.

Then capture a series of images at varying ISO settings, starting at the base ISO for your camera and increasing in perhaps one-stop increments. So you might capture an image at 100 ISO, then 200, then 400, then 800, and so on, until you reach the maximum ISO setting (or the maximum setting that you actually want to test).

As you raise the ISO setting, you may find that the wide-open aperture causes you to be unable to achieve a proper exposure with the available range of shutter speeds, so you may need to stop down the lens as part of the capture sequence.

You might also want to capture longer exposures in a similar manner, both with in-camera long exposure noise reduction turned on and turned off.

When it comes time to review the results of this testing, keep in mind that in most cases the software used to generate previews from raw captures will apply some noise reduction by default. You therefore may want to process all of the captures in a batch with default adjustment settings but with noise reduction disabled.

By reviewing the series of captures (and the metadata for each of them) with no noise reduction applied, you’ll get a clear sense of how much noise you can expect at different camera settings. Again, in particular this would mean evaluating results at various ISO settings, but you’ll also want to see how your camera performs with long exposures of varying durations.

After reviewing your results, you’ll have a much better sense of the noise behavior of your camera, as well as what sort of limits you might want to employ to help ensure minimal noise whenever possible.

Determining Base ISO


Today’s Question: How do I determine the optimal ISO for my camera? I don’t remember anything like that in the manual or specifications when I bought my camera.

Tim’s Quick Answer: As a general rule the “base” ISO for a camera will be the lowest ISO setting available using the normal control for the camera. The special “low” ISO options available on some camera models would not generally be the base ISO.

More Detail: As noted in a recent Ask Tim Grey eNewsletter, in most cases you can expect the least noise and best overall image quality by using the “base” or “native” ISO setting for your camera. In most cases, that base ISO will involve the least amount of amplification to the signal being gathered by the image sensor, which translates into less noise and greater dynamic range.

There are, of course, some exceptions in terms of how specific cameras function or the results you can achieve at various settings. And, of course, as many photographers have found, it isn’t always easy to find out which ISO setting is the “base” setting.

For most digital cameras you will find that an ISO setting of 100 (or sometimes 200) represents that base ISO. As noted above, in most cases the lowest setting you can set with the normal ISO adjustment control on the camera will typically be the base ISO that will provide the best image quality. The “extra” settings with a lower value that are typically found on a separate menu control for cameras with such an option are generally not the base ISO setting, and won’t necessarily provide improved image quality.

Again, there are many variables involved among the different camera manufacturers and models. That is why I always recommend performing some testing of your own to get a sense of the impact various ISO settings have on noise levels for your camera. In particular, this type of testing can help you get a better sense of how high you can raise the ISO setting before you start to see problematic noise in your images.

Embedded Previews


Today’s Question: With a high-resolution camera do you recommend making use of the embedded preview option in Lightroom Classic CC rather than generating Standard previews on import?

Tim’s Quick Answer: On balance, I still recommend using the Standard (or 1:1) preview option in Lightroom rather than making use of the embedded previews that are included in proprietary raw captures.

More Detail: Choosing the option during import to use the embedded previews rather than generating Standard (or 1:1) previews could potentially speed up your workflow a little bit, since the embedded previews are already available and Lightroom would therefore not need to perform any additional work to generate replacement previews.

However, the embedded previews won’t necessarily match Lightroom’s interpretation of the photos, since the embedded previews are generated by the camera rather than Lightroom. Also, those embedded previews would not reflect Lightroom adjustments, such as if you had applied a Develop module preset during the import process. I apply profile-based lens corrections at import, for example, so all photos will have that correction by default. The embedded preview would not reflect those changes.

So, on balance I still prefer to have Lightroom generate the Standard previews during import. It takes a little extra time as part of the overall import process, but I feel that is time well spent.

Double Save Confusion


Today’s Question: When preparing a copy of an image in Photoshop for online sharing, after I save my JPEG and try to close the image, Photoshop asks if I want to save my changes. But I just saved the image! Why is Photoshop asking me about saving changes when I just saved my image?

Tim’s Quick Answer: The description makes it clear that the image in its current state is not supported by the JPEG image format. Therefore, Photoshop is asking you to save the image in order to preserve all features you have taken advantage of. If you don’t want to preserve those features, you could simply save the JPEG and then opt not to save the “second” time.

More Detail: There are a variety of features you can leverage in Photoshop that are not supported by a JPEG image file. For example, you can’t save a 16-bit per channel image as a JPEG. JPEG images also can’t include layers, saved selections, alpha channels, among certain other limitations.

If you have an image open that includes features not supported by the JPEG image format, you can generally still save the image as a JPGE. For example, let’s assume you are working with an image in the 16-bit per channel mode. You can still choose File > Save As from the menu and save the image as a JPEG, and that JPEG file will automatically be created in the 8-bit per channel mode.

But after saving that JPEG file, the image in Photoshop will still be the 16-bit per channel image you had been working with. Therefore, after saving a JPEG copy and closing the image in Photoshop, you’ll be prompted to save the image because at that point the full image (or the changes you’ve applied if the image had been previously saved) will not have been saved.

So, just because you’ve saved a JPEG copy of the image doesn’t mean you’ve saved all features of the image you’re working with. When that situation exists, Photoshop tries to make sure you’re not losing any unsaved changes based on the lack of support for certain features with JPEG images.

Distant Depth of Field


Today’s Question: How much should I stop down my lens aperture if I want to achieve optimal depth of field when photographing with a long lens from a long distance from a landscape?

Tim’s Quick Answer: When photographing a scene from a considerable distance, you might be surprised at how much depth of field you can achieve even if you don’t stop the lens aperture down much (or at all). When focusing at a distance of about one-quarter of a mile with a 200mm lens, for example, stopping down to f/8 will provide a depth of field that covers the full scene all the way to infinity.

More Detail: This was a question asked by a workshop participant while we were atop Steptoe Butte in the Palouse region of eastern Washington State. That means we were about one thousand feet above the surrounding terrain. Even assuming you are focusing on a portion of the scene relatively close to the base of the butte, your focus point would still be about one-quarter of a mile or so. If you were using a 200mm focal length, at f/8 you could have everything from about 500 yards to infinity in focus.

I think many photographers who have experience with landscape photography tend to think it is always necessary to stop down to f/16 or f/22 to achieve any significant depth of field for a scene. When using a lens with a longer focal length, of course depth of field becomes a more significant concern. But when you are focusing at a considerable distance, you will have greater depth of field. I often find photographers are surprised at just how much depth of field they will achieve when focusing from far away, even with a long lens.

When you combine a distant focus point with a longer lens that will be capturing a relatively narrow field of view, there’s a good chance that even with a relatively shallow depth of field you will still be able to have the full scene in focus. For example, even a 500mm lens focusing at a distance of about one-quarter mile will provide a depth of field that is about 500 feet deep. That may very well provide adequate depth of field for the full scene, considering the narrow field of view with a 500mm lens.

When focusing close, such as with macro photography, getting enough depth of field can be a challenge. But when focusing from a considerable distance, you may be surprised at just how much depth of field you can achieve, even without stopping down the lens significantly.