Category: Ask Tim Grey

Today’s Question: Sometimes Photoshop offers me a choice of square pixels or other kinds of pixels. I thought pixel was just a pixel. Can you explain?

Tim’s Quick Answer: For photographic images, pixels are indeed generally square. The option for non-square (i.e., rectangular) pixels relates primarily to the creation of images for certain video formats.

More Detail: For the vast majority of imaging software used for still photos and illustrations, square pixels are the standard. Even in high definition (HD) video, square pixels are the norm.

However, there have been a variety of video formats (primarily standard definition or SD video) where rectangular pixels were used. This was mostly an issue related to increasing overall resolution without changing the number of “scan lines” in the video itself. The number of scan lines represents the number of physical rows of pixels on older analog devices, such as CRT (cathode ray tube) displays.

For the most part, you can ignore the fact that it is possible to create images using non-square pixels in Photoshop. This option is really there to provide compatibility with the maximum range of video formats, since Photoshop provides a variety of (quite powerful) features for working with video clips.

Today’s Question: What is the advantage of the “Create Saved Print” option in the Print module in Lightroom? I save the images I print to a Collection but maybe this is a better option?

Tim’s Quick Answer: The primary reason to use the “Create Saved Print” option in Lightroom’s print module is so you can quickly and easily reproduce the exact same print layout (including the same photos). In other words, this option is most helpful for scenarios where you want to be able to produce the same print multiple times.

More Detail: When you choose the “Create Saved Print” option (found at the top-right of the preview area in the Print module) you are actually creating a “special” collection for the image (or images) included in the current print job. That includes the overall layout for the print in addition to the actual images included in the print.

What this all translates to is that if you need to produce print a given image at the same size and overall layout, you can simply choose the saved print, confirm the print settings, and print the image.

As you can probably appreciate, this option is most helpful for photographers who are selling prints. You can create saved prints of your most popular images for the specific print sizes you offer, so that it is easier to quickly create additional prints for those images.

For photographers who don’t sell their images as prints, this option is less useful. That said, in some situations it may be helpful to save some print layouts, so you can quickly reproduce a given print multiple times as needed.

Today’s Question: Can you create a Triptych in Lightroom, and if so do you have any helpful hints on how to do it?

Tim’s Quick Answer: You can create a Triptych in Lightroom by combining three images on a single page in the Print module. In fact, there is a “Triptych” template in the Print module that serves as a great starting point for this project.

More Detail: The Triptych template in the Print module in Lightroom places three square images on the page, but you can modify this layout to suit your personal preferences.

Before you get started creating your Triptych you’ll want to be sure that the images you want to include are shown on the filmstrip on the bottom panel. You can navigate to a folder, apply a filter, or employ a collection to ensure the desired photos are on the filmstrip.

Next, go to the Print module and choose the Triptych template from the Template Browser on the left panel. You can then click the Page Setup button to choose the paper size you want to print to as well as the orientation (portrait versus landscape) for the print. Click OK in the Page Setup dialog to apply the changes.

At this point you can choose the “Selected Photos” option from the Use popup on the toolbar below the print preview area and select the photos you want to include in the Triptych. You can also adjust the order of the images on the filmstrip to change the order of the images in the Triptych.

You can also adjust the settings on the right panel to fine-tune the overall look of the Triptych. For example, if you want to use non-square images in the Triptych you can turn off the “Keep Square” checkbox in the Layout section of the right panel and adjust the Cell Size sliders to adjust the size of the cells that contain the images in the print layout.

When you’re finished creating your Triptych layout, you can of course print the final result. You can also save the resulting layout as a JPEG image by choosing the “JPEG File” option from the “Print to” popup in the Print Job section of the right panel.

Today’s Question: When I worked in a photo lab, we had to recalibrate every time we used a new paper batch (even if it was the same paper) and/or replenished chemicals. Is it necessary to run a new profile each time I open a new box of the same paper or change an ink cartridge?

Tim’s Quick Answer: In theory yes, but in reality this isn’t generally necessary because the manufacturing tolerances for today’s photo inkjet papers and inks are quite high.

More Detail: What we refer to as a “printer profile” is really a profile for the specific printer, ink, and paper combination used to build the profile. After all, you used a specific printer to print the target color swatches, and printed those color swatches using a specific inkset with a specific paper.

However, the printers of a given model from a single printer manufacturer are generally produced with manufacturing tolerances that ensure relatively consistent results. Paper manufacturing and ink production similarly have high tolerances, so from one batch to the next there will generally not be a tremendous variation.

To be sure, there is something to be said for precision. But if you felt the need to build new profiles for each new pack of paper you buy, you could also argue that you should produce individual printer profiles for the specific environmental conditions under which the profile is being created and the final prints will be made.

I do think it is a good idea to update custom printer profiles from time to time. For one thing, there can be unintended variations in manufacturing over time. In addition, you won’t necessarily know when the manufacturer has made changes in their manufacturing process for a given paper type. But I also think there is no need to go overboard when it comes to creating custom printer profiles.

Many photographers are happy with the “canned” printer profiles included with the printer driver or available from third-party paper manufacturers. In my experience those profiles are actually of very high quality and accuracy these days, which is not something I could say in the earlier days of digital printing.

That said, a custom printer profile can be tremendously helpful when critical accuracy in the print is important to you. If so, you might consider having a service provider produce profiles for you, or purchasing a package for building your own profiles, such as the X-Rite ColorMunki Photo package you can find here:

http://timgrey.me/munkiphoto

Today’s Question: What is the connection between the profiles of the computer display, the profile embedded in an image, and the profile of the paper onto which you print?

Tim’s Quick Answer: In essence, all of these profiles are helping to translate the color in your images as those images move through your workflow. The display profile helps ensure that the display presents an image accurately, the embedded profile describes the colors as they are used in the image, and the printer profile describes the behavior of the printer.

More Detail: It is easy to assume that profiles shouldn’t be necessary. After all, can’t we just describe what color we want and always get that color? In the real world, color isn’t that simple.

To begin with, there are limitations related to the devices that present our images. A monitor display can only present a specific range of color values, and a printer can only produce a certain range of colors based on the specific inks and paper being used, and an image can only include colors based on the color space being used to adjust that image.

The embedded profile for the image (or the working space profile if there isn’t an embedded image) describes the color values contained within the image. Generally speaking this involves mapping the RGB values for the pixels within the image to the Lab color space that is generally used as a reference color space in color management. So, the embedded profile helps to describe color more accurately for a given image, within a variety of different contexts.

When you view an image on your monitor, the display profile helps to compensate for the fact that the embedded profile for the image may not map directly to the native behavior of the monitor display. In other words, the display profile reflects the behavior of the specific monitor you are using, and enables a compensation based on that behavior so the colors in your image will be presented as accurately as possible.

Finally, the printer profile compensates for the specific behavior of a given printer, ink, and paper combination. In much the same way that a display profile ensures that an image is displayed on the monitor as accurately as possible, the printer profile ensures that the print reflects the colors in the image as accurately as possible.

You can think of profiles in the context of a color-managed workflow as being tools for translating colors across a variety of output devices and conditions. In many respects you can think of profiles as a way to translate from one color language to another without losing the meaning of the various colors involved. There are, of course, limitations that can reduce the overall accuracy of colors presented, but profiles help minimize those issues.

To learn more about color management, check out my video course “Color Management for Photographers” in the GreyLearning library. You can save $15 off this course by starting with this link:

http://timgrey.me/greycolor15

Today’s Question: I really enjoyed reading your article on the back button focus technique in the July issue of Pixology and I picked up a couple of neat tips. I’ve been using this technique for some time but have some confusion around using this option along with continuous focus/predictive autofocus. Specifically, how do I ensure that a moving subject will be in focus at the time the shutter releases? A great example of my question comes from viewing your “Parting Shot” at the end of the issue. In this picture you have a crop duster plane coming straight at the camera, at some speed I’m sure. How did you manage to keep the plane in such sharp focus? Were you using back button focus for the shot? If you held down the back focus button while pressing the shutter release, will the camera use predictive autofocus?

Tim’s Quick Answer: Back button focus will trigger predictive autofocus as long as your camera is otherwise configured for that purpose. In the case of the crop duster shot (which you can view here: https://500px.com/photo/112385163/crop-duster-spraying-in-palouse-by-tim-grey), I was indeed using back button focus, and that was triggering predictive autofocus.

More Detail: The key here is to configure your camera for continuous autofocus when you enable back button autofocus. You can then choose whether you want “one shot” versus “continuous” autofocus based on your use of the back button for focusing.

When the back button is pressed and held, the camera will focus based on the current settings. If you have the camera set to a “one shot” autofocus mode, then pressing and holding the back button for autofocus will only enable “one shot” autofocus.

If you have enabled continuous autofocus, pressing and holding the back button focus button will trigger continuous autofocus. And this is where one of the most powerful features of back button focus comes in.

By configuring your camera for continuous autofocus and enabling back button autofocus, you have the best of both worlds. When you want continuous autofocus you press and hold the back button focus button. When you want the equivalent of “one shot” autofocus you press the button until focus is established, then release the button.

It is worth noting that autofocus in general can become even more powerful by selecting a specific focusing point within the viewfinder that corresponds to the position of the key subject within the frame. That is exactly how I captured the crop duster photo referenced above.

If you’d like to get a free copy of the Pixology magazine issue that features the article on back button focus, you can sign up to get that issue for free here:

http://timgrey.me/pixbackfocus

Today’s Question: I am confused by comments from various photographers saying that one RAW processor is better than another. Is it possible to make adjustments so that the results of one RAW processor can be matched to any other RAW processor?

Tim’s Quick Answer: All RAW processing software is not created equal. Some software will indeed produce better results than other software, and it can be very difficult to achieve the exact same appearance when processing the same image with different software tools.

More Detail: Each software tool for processing RAW captures uses its own algorithms for both translating the RAW capture into actual pixel values and applying adjustments to the appearance of those pixels.

For example, you will find differences in the ability of different RAW processing software to extract shadow detail. You will also find significant differences when it comes to minimizing noise in your photos. The specific adjustments that are available will vary, and the range of possible results may vary as well.

To be sure, the overall level of quality that can be achieved by most RAW processing software is very good. In the early days of digital capture you could find dramatic differences in image quality with different software for processing RAW captures. Today I would say there is less variation in terms of quality. However, there is still variation in terms of the specific approach used by different software tools, as well as variation in the specific adjustments available.

However, it is very important to test software yourself rather than relying on reviews from others. I have seen far too many reviews where similar adjustment settings were used between different RAW processing software, with a clear difference in the final result. This seems to indicate that one software tool is better than another for RAW processing, with the result somewhat exaggerated in a way that I would consider unfair.

Instead of relying on reviews from others, I recommend testing out various RAW processing software to see which one works best for you. Try to achieve an ideal adjustment for the same image using different software, and then decide which might be best for you in terms of the quality of the result, the workflow efficiency, the ease of use of the software, and other factors.

Your final decision will depend on your own priorities and preferences, the types of images you tend to capture, and other factors. But the bottom line is that there are differences among RAW processing software, and it isn’t always possible to achieve the exact same result among different software when processing the same image.

Today’s Question: I just purchased a 10-stop neutral density (ND) filter. Could you advise on how to calculate exposure times?

Tim’s Quick Answer: The process of calculating exposures when using a neutral density (ND) filter can actually be very simple. Start with exposure settings that are proper for the scene without the ND filter, using the Manual exposure mode. Then add the ND filter and adjust the shutter speed by the number of stops indicated for the density of your ND filter.

More Detail: In essence, I recommend starting off as though you weren’t using an ND filter at all. Get the camera setup without the ND filter attached to the lens. This makes it much easier, among other things, to compose your photo.

You can use whatever method you want to determine the appropriate exposure settings, but you’ll want to end up in the Manual exposure mode. If you’re not comfortable using Manual mode to establish the initial exposure, you can start with a semi-automatic exposure mode (such as Aperture Priority) to determine appropriate exposure settings. Then switch to Manual exposure mode and dial in the exact same settings.

It is worth noting that under most circumstances I will start off with the ISO at the minimum value and the aperture at the smallest opening (largest f-number) when capturing a long exposure photo that employs an ND filter. However, part of the benefit of using an ND filter is that you can get a relatively long exposure even with an aperture that isn’t stopped down all the way. This enables you to, for example, create a long exposure that also has a narrow depth of field.

Once you have determined your exposure settings and have everything else configured (such as composition and focus), you can add the ND filter. It is worth noting that the Xume Adapters (http://timgrey.me/go-xume) I’ve talked about in the past make this step much easier, since the ND filter can then snap into place using magnets.

With the ND filter attached, the final step is to adjust the shutter speed based on the number of stops of light being blocked by the ND filter. In this case, for example, the question relates to a 10-stop filter.

Generally speaking, your camera will adjust shutter speeds using one of the dials on the camera, in either half-stop or third-stop increments. In other words, you will turn the dial either two or three “clicks” for each stop. Make sure you’re turning in the direction to extend the exposure time, not shorten it. Then turn by 20 “clicks” if your camera is set to half-stop increments and 30 “clicks” for third-stop increments.

I am in the habit of counting out stops of light based on sets of clicks. I generally have my camera set to adjust exposure in half-stop increments, so for each two clicks I will count off a stop. To me this is a little easier than counting out twenty clicks, for example.

Overall the process here is very simple. Setup your camera based on no ND filter being used, then add the filter and adjust the shutter speed by the number of stops needed for that filter.

Today’s Question: How do I capture long exposures at night without blowing out the windows of the buildings?

Tim’s Quick Answer: There are a few options here. The first is to set your exposure to retain detail in the brightest areas (in this case the windows of buildings). The second is to create a high dynamic range (HDR) image. The third is to not worry about the lost detail. And the fourth is to capture your images earlier in the evening before the contrast is so extreme.

More Detail: The problem with creating a night exposure that retains all detail in the bright lights (such as windows of buildings where the lights are on) is that the rest of the image will generally be extremely dark. As a result, if you want to capture only a single image you’ll need to choose between detail for the highlights versus detail for the shadows.

Creating an HDR image is a reasonable option that can greatly improve the overall tonal range represented in the final image. However, with long exposures there are some inherent challenges to HDR. To begin with, it can require considerable time to capture all of the images in the HDR sequence. On a related note, the longer time required to capture all of the images can result in problematic changes within the scene from one capture to the next.

My recommendation is to shift your night photography to earlier in the evening. If you capture your long exposures late enough that the lights of the city are on, but early enough that there is still some degree of illumination left in the sky, you’ll have a narrower range of tonal values to contend with, so you will be better able to capture the full range (or nearly so) with a single exposure.

Note, of course, that you can employ a neutral density filter to extend the exposure longer that would otherwise be possible when photographing in the relatively early evening. But in general, if you photograph as soon as the lights of the city are turned on, you should be able to achieve excellent results with a single frame, likely without the need for a neutral density filter.

Today’s Question: Is there a way to flip a selection in Photoshop?

Tim’s Quick Answer: Yes, of course. You can both invert and flip a selection, using the Inverse command if you want to invert the selection, or the various Transform commands to flip the selection horizontally or vertically.

More Detail: If you want to invert a selection so that the deselected area is selected and vice versa, you can choose Select > Inverse from the menu. This will reverse the selection so that you have the opposite of the original selection.

Before using the general Transform commands to change a selection, first you need to put the selection itself into “transform” mode. To do so, with an active selection choose Select > Transform Selection from the menu. You can then use the various Transform commands on the Edit menu to actually transform the shape of the selection.

If you want to flip a selection horizontally or vertically, you can use the Transform commands. For example, you can choose Edit > Transform from the menu, and then choose Flip Horizontal or Flip Vertical from that submenu based on the direction you want to flip the selection.

There are also a wide variety of other commands available on the Edit > Transform submenu, which can also be used to manipulate the shape of a selection. You can also access the equivalent of the Free Transform command by choosing Select > Transform Selection from the menu.

It is also worth noting that if you have used a selection as the basis of a layer mask, you can also apply the Transform commands (among other commands) to change the shape of the layer mask.