Ask Tim Grey

Today’s Question: In reference to the recent question involving Xume Adapters, do these introduce any issues with vignetting on extreme(16-35mm) wide angle lenses? These adapters seem like a great idea but I’m concerned that the Xume system will position the filter farther away from the front of the lens than it would be if it were normally attached.

Tim’s Quick Answer: Yes, for focal lengths shorter than about 24mm on full-frame sensors there is some vignetting introduced by the Xume Adapters, due to the filter being positioned further from the front lens element than would otherwise be the case.

More Detail: I know that the fine folks at Xume Adapters are aware of this issue, and that they are exploring options for mitigating the vignetting with wide-angle lenses. In the meantime, the Xume Adapters are best used with lenses with focal lengths of about 24mm or greater, or the equivalent focal length for cameras with other than a full-frame sensor.

For those photographers who are interested in learning more about the potential for Xume Adapters, you can see them in use in an episode of Tim Grey TV found here:

https://youtu.be/qfOdqsC457s

Today’s Question: Please, help me clarify a big doubt. I have a Canon 5D Mk III (22.6 Megapixels, 5760 x 3840). With an image that “big” (22 megapixels), if I were to print it using a printer with a maximum printing resolution of 2880 x 1440 dpi, how big can I print an image without any interpolation? The printer is an Epson and the maximum printing area is 17×22″.

Tim’s Quick Answer: The dot per inch (dpi) resolution indicated for the printer (for example, 2880 dpi) relates to print quality, not to the maximum potential output size. To determine the output size without resizing the native capture, you need to calculate based on the resolution used to render the image. In general you can assume a resolution of somewhere between 300 and 400 pixels per inch. Thus, your 22 megapixel captures can be printed at 11×16 inches without resizing (and even bigger with some resizing).

More Detail: The actual resolution used by the printer software to render image data for printing varies from one printer to the next. In general this resolution falls somewhere in the range of about 300 pixels per inch (ppi) to about 400 ppi. Many Epson printers, for example, use a resolution of 360 ppi, although some newer models actually use 720 ppi.

The reason the “advertised” resolution for the printer is higher then the “actual” image resolution is that the printer specifications refer to droplets of ink rather than pixels in the image being printed. As you can imagine, it requires multiple droplets of ink to produce the specific color for each pixel in a photo.

So, in this case let’s assume an image resolution for printing of 360 ppi. You can then divide the pixel dimensions by the resolution value to determine the native output size. So, 5760 pixels divided by 360 ppi is 16 inches, and 3840 pixels divided by 360 ppi is about 10.7 inches. Thus, a native maximum output size of about 11×16 inches.

However, it is very important to keep in mind that you can enlarge an image and still retain excellent print quality. As a general rule of thumb I would say you can feel very comfortable doubling the dimensions of a photo, as long as the original capture is of very good quality. That would enable you to produce a print of about 22×32 inches in this case, for example. And in reality, the larger the print size the greater the typical viewing distance, so you can often “get away with” an even larger print size.

To be sure, it can be very helpful to understand the “native” print size potential for the images you’re capturing. Just don’t forget that you can still achieve excellent results when enlarging a high-quality photo to produce a larger print.

Today’s Question: Perhaps I’m just being stubborn here, but I don’t like the new welcome screen that is included in the latest version of Photoshop. Is there a way to disable this new feature so I just have an empty interface when I start Photoshop?

Tim’s Quick Answer: Yes, you can disable the new “Start” screen. Simply turn off the “Show ‘Start’ Workspace When No Documents Are Open” checkbox on the General page of the Preferences dialog and restart Photoshop.

More Detail: In the latest version of Photoshop the new Start workspace appears in when you launch Photoshop without any images open. This new Start screen provides quick access to recently opened images, links to educational tutorials, and other options. While this new screen can certainly be helpful, it can also be a little distracting. Fortunately it is easy to disable this new Start screen.

To get started, go to the Edit menu on the Windows version of Photoshop or the Photoshop menu on the Macintosh version. Then choose Preferences > General from that menu. Turn off the “Show ‘Start’ Workspace When No Documents Are Open” checkbox and click OK to close the Preferences dialog. Quit Photoshop, and from that point forward when you launch Photoshop the “Start” workspace will no longer be displayed.

Today’s Question: I’m working on improving my understanding of the Clone Stamp tool in Photoshop, including the options on the Clone Source panel. But I can’t figure out what the “Auto Hide” option does. I’ve searched and searched, but every explanation I can find pretty much just says that “Auto Hide” will automatically hide the source, which doesn’t really explain much of anything. I’m not seeing any effect! What am I missing?

Tim’s Quick Answer: For typical use with a photographic image, the “Auto Hide” checkbox on the Clone Source panel won’t have any visible effect for the Clone Stamp tool. That is because under normal circumstances you are painting the same pixels that would otherwise be previewed. But if you alter the behavior of the Clone Stamp tool, such as by reducing the Opacity setting or changing the blend mode on the Options bar, you will see that with “Auto Hide” turned on the “Show Overlay” preview will hide when you start painting.

More Detail: The “Show Overlay” checkbox for the Clone Stamp tool can be found on the Clone Source panel, which in turn can be brought up by selecting Window > Clone Source from the menu bar. With the “Show Overlay” checkbox turned on, your mouse pointer will show a preview of the pixels that will be painted with the Clone Stamp tool, based on the source of pixels you have selected.

This option can be tremendously helpful when you need to align the source pixels into the destination area with precision, such as to maintain alignment of textures in the photo.

The “Auto Hide” option will cause the overlay preview to be hidden as soon as you start painting with the Clone Stamp tool. However, as noted above, under normal circumstances this translates into hiding the pixels you are painting while at the same time showing you the pixels you are painting. In other words, there is no visible effect with the “Auto Hide” option turned on compared to when it is turned off.

However, that is only because the preview and your painting will be a perfect match with each other. If you reduce the Opacity on the Options bar for the Clone Stamp too, the “Show Overlay” preview will be presented at full opacity, while the actual painting you perform will appear at a reduced opacity. In this scenario, having the “Auto Hide” option turned on will cause the “Show Overlay” preview to appear at full opacity when you are not painting. Then, when you start painting the full-opacity overlay will be hidden, and you will only see the painting you are performing with the Clone Stamp tool appear at the reduced opacity. The same concept applies to other settings that alter what you are painting with the Clone Stamp tool, such as the blend mode option.

What this all means for most photographers is that you can pretty much ignore the “Auto Hide” checkbox. But it may also be helpful to understand the specific behavior of this option, in the event it is ever useful for the specific cleanup task you’re performing for an image.

Today’s Question: A while back you commented on the watermark ‘issue’ that your preference was not to use any type of watermark as it detracted from the image, and does little to deter ‘theft’ of the photo. While I agree for the most part with your statement, I also felt that it ‘could’ add to the photo, and ‘credibility’ of the photographer. I do enjoy posting my photos on line (e.g., Instagram), but have always been leery of someone using/taking a photo without my permission. However, I noticed the other day that you posted a photo to Instagram with a watermark. Now I’m wondering if you’ve changed your perspective on this, and if not, why the watermark?

Tim’s Quick Answer: I have not changed my perspective on watermarks. I generally prefer not to have watermarks on my images. I also don’t personally worry about theft of my images. When I add a watermark to an image it is only because I either was hoping for a little self-promotion, or was teaching someone how to add a watermark to a photo.

More Detail: To be sure, a watermark on a photo can be valuable for promotional purposes. From this perspective, since I do very much want to promote myself through my photography, it would make perfect sense for me to include a watermark on photos when I share them. That watermark could simply feature my name, or my website address, for example.

However, in general I prefer not to have a watermark on my photos for purely aesthetic reasons. My hope is that I will get enough of a promotional benefit by virtue of the context of sharing the photo, even without a watermark. So, for example, when I share a photo on Instagram (http://www.instagram.com/timgreyphoto) my hope is that if someone sees a photo they like they will follow me and look at my profile and perhaps visit my website.

Much of this is philosophical, of course, and not necessarily the most effective approach in terms of self-promotion. But personally I prefer to take an approach that is a bit more subtle in terms of promotion (even though I’m not exactly subtle in most other ways).

And again, my personal preference is to not employ a watermark for purposes of deterring theft. I don’t believe that theft will really be prevented by a watermark that doesn’t significantly interfere with the photo, and I prefer not to have a watermark that interferes with the enjoyment (I hope!) of my photographic images.

Obviously all of this represents my personal preference. I prefer to only use a watermark when it provides some degree of promotional benefit, not as a theft deterrent. But I certainly understand the desire to take more significant steps to prevent the theft of photos. I simply define my priorities a little differently than other photographers (and I certainly realize that my priorities don’t necessarily align with those of many other photographers).

Today’s Question: Could you explain more this statement that was in a prior “Ask Tim Grey”:

“back button autofocus enables you to separate the metering functions of your camera from the focus functions”

Am I right that only the shutter button meters the scene? So if I want to meter a spot on the upper left of the scene but want to focus on low center, how would I do that?

Tim’s Quick Answer: The “back button” focus option available on many cameras obviously enables you to separate the focus and exposure metering features. If you also want to lock the exposure, you’ll either want to employ the auto exposure (AE) lock feature, or employ the Manual exposure mode.

More Detail: In most cases exposure metering on a camera is triggered by the shutter release button. You can generally press the shutter button halfway to initiate the automatic exposure, and then press the button the rest of the way to actually take the photo. But in your example you want to be able to re-frame the scene after establishing exposure settings based on metering in a specific area of that scene.

Obviously you could employ the Manual exposure mode to lock in specific exposure settings. Then it doesn’t matter how you reframe the scene, because the exposure won’t change based on the changes in lighting as you change the framing.

If you want to use one of the exposure modes that enable automatic exposure, you’ll need to actually lock that exposure. Otherwise when you reframe the scene you’ll also cause the metering to update and the exposure settings to change.

The specific options available and method of employing auto exposure lock will differ from one camera to the next. But the basic idea is very straightforward. You can point your camera to the area you want to meter on and press the shutter release button halfway to actually establish exposure settings based on that metering. Then press the “AE Lock” (or similar) button to lock the exposure based on those settings. You can then reframe the scene without the exposure settings changing.

In some cases you simply press and release the AE Lock button to lock the exposure for the next photograph. In other cases you need to press and hold that button. And in some cases you can change the behavior through menu options on your camera. But the point is that many cameras do indeed feature an AE Lock feature.

Making use of “back button” focus along with AE Lock enables you to exercise considerable control while still taking advantage of the automatic features of your camera. You can set focus in one area, establish exposure based on another area, and then frame up the scene without altering focus or exposure settings.

Today’s Question: When I talked to you at an event a few months ago, you mentioned a lens cap that attached magnetically. Can you remind me where I can find that lens cap?

Tim’s Quick Answer: The lens cap I’m using is from a company called Xume Adapters. They produce magnetic filter holders (which I love), as well as a lens cap (which is incredibly convenient). You can find the 77mm version of the lens cap here: http://timgrey.me/77xcap.

More Detail: To my knowledge, the lens cap is not currently available in sizes other than 77mm. And it is important to note that the lens cap is really an accessory to the filter adapters offered by Xume Adapters. So, for example, if you get a set of adapters so you can easily swap filters on a given lens, in place of a filter with a magnetic adapter you can place the Xume Adapters lens cap on the lens, provided the magnetic adapter for the filters is already attached to that lens.

In other words, the lens cap from Xume Adapters makes use of the same functionality as the filter adapters they offer. You can see the Xume Adapters in action (though only for filters, not the lens cap) in an episode of Tim Grey TV via YouTube here:

https://youtu.be/qfOdqsC457s

Today’s Question: I just got a new MacBook Pro, which is my first Macintosh. I have gotten Photoshop installed correctly, but now when I use the “Command+Spacebar” keyboard shortcut to access the Zoom tool, a Spotlight search window shows up. Is there a way to disable this option so the shortcut only works in Photoshop?

Tim’s Quick Answer: You can disable the Spotlight search keyboard shortcut on the Macintosh. To do so, first choose System Preferences from the Apple menu on the menu bar. Then choose Spotlight in the System Preferences window, and click the Keyboard Shortcuts button at the bottom-left of the window. Turn off the checkbox for “Show Spotlight search”, and the keyboard shortcut will be disabled.

More Detail: In addition, you can change the keyboard shortcut for Spotlight search, so that it won’t conflict with Photoshop. To do so, instead of turning off the checkbox for “Show Spotlight search”, click on the keyboard shortcut to the right of that checkbox. Then press a key keyboard shortcut combination on the keyboard to assign a new keyboard shortcut. Of course, finding a keyboard shortcut that won’t conflict with the other applications you use may be a challenge!

Personally, I prefer to turn off the keyboard shortcut for Spotlight altogether. When I want to perform a search I can then simply use the search text field on any Finder window, or click the magnifying glass icon at the far right of the menu bar to bring up the Spotlight search window.

Today’s Question: I scanned a 35 mm slide at maximum resolution (11×17 at 300 pixels per inch). I want the print to be 19 inches (on the long side) and to be as sharp as possible. Will I get better quality if I have Photoshop interpolate the (extra) pixels to adjust the image size, or is it better to reduce ppi (to around 270) to keep the same size file?

Tim’s Quick Answer: My recommendation is to first scan your original transparency at the maximum optical resolution of your scanner. After optimizing and saving your master image, create a copy and resize that copy in Photoshop to the intended print dimensions, at a resolution optimal for your print process.

More Detail: The numbers provided in the question suggest a scanner resolution of about 3,300 pixels per inch. This is based on a 35mm slide scanned to produce an image that is 3,300 pixels on the short side (11 inches at 300 pixels per inch). Since the short side of a 35mm slide is about one in in size that translates to about 3,300 pixels per inch. If the scanner actually offers a higher resolution (such as 4,000 pixels per inch) I recommend scanning at that higher resolution.

After applying all of the adjustments you feel are necessary to optimize the image, I would then save that final result (with all layers intact) as a Photoshop PSD image or a TIFF image. This file can now server as your “master” image for all future output.

When you want to make a print, you can create a copy of your master image, flatten that copy, and resize to the intended print size. I recommend performing that resizing step in Photoshop, although in actual fact today’s printer software also does an excellent job of resizing the final image at high quality.

I recommend resizing the image to be printed based on the “native” resolution of your printer in terms of how image data is processed. This varies among different printers, but in general is around 300 or more pixels per inch. For many photo inkjet printers a resolution of 360 pixels per inch is optimal. But again, the specific number varies based on your printer, and can often range from around 300 pixels per inch up to around 720 pixels per inch.

Let’s assume a printer that renders the final output data at 360 pixels per inch. If you leave the image resolution at 270 pixels per inch in order to not apply any interpolation (or to keep the file size smaller), that image data is still going to be interpolated upward. If you give the printer less data than it needs (360 pixels per inch in this case), the printer software will simply interpolate the image data up (from 270 pixels per inch in this example) to the necessary output resolution. In other words, you may as well resize the image to the final output dimensions in Photoshop rather than having the printer software perform that additional work.

This issue used to be more significant than it is today, because printer software didn’t do as good a job of interpolation, especially compared to Photoshop. However, today’s printer software actually does an excellent job with this interpolation. So resizing to the final output dimensions in Photoshop before printing is not quite as important as it used to be, but I do still recommend this approach as a best practice when printing.

Also note that once the image has been resized to the final output dimensions, you should apply sharpening to optimize that final print. And, of course, sharpening is best applied at the final output dimensions, which is one additional reason to resize in full in Photoshop. That way the sharpening truly is the final step, rather than resizing in Photoshop, then sharpening, only to have the printer software apply a further change in the pixel dimensions during the print process.

Today’s Question: I see some photographers use a lens hood all the time, others only when in strong sun, still others (like me) never. Should I be using a lens hood all the time? Does it alter exposure, make metering more accurate, or offer some other advantage?

Tim’s Quick Answer: The key purpose of a lens hood is to prevent lens flare. Thus, in concept you only need to use a lens hood when the sun position is “in front” of a line formed by the front element of your lens. If the sun is “behind” the front of the lens, the lens itself will provide shade to prevent lens flare. Thus, it is a good idea to always use a lens hood.

More Detail: There are a few points to keep in mind when it comes to lens hoods. As noted above, a lens hood is only truly necessary when the sun is “in front” of the lens. But in reality it is important to keep in mind that you are likely to change your viewing angle from time to time when photographing. In other words, just because the sun is behind you initially, that doesn’t mean it will remain in that position for every photo you capture.

Also, it is important to realize that the “funny” shape of many lens hoods is very much intentional. Each lens hood is designed for the specific lens it is intended to be used with in terms of preventing lens flare without creating vignetting or other artifacts. Therefore, you should always be sure to use a lens hood specifically designed for the lens you are using.

In addition, while a lens hood is really intended primarily to prevent lens flare, it is worth noting that keeping the lens hood on the front of the lens can actually help protect that lens. If you bump a lens into a wall, for example, it is generally preferred to have the lens hood hit the wall rather than the front lens element.

As a bonus, having a lens hood attached to the front of the lens makes you look like a more intelligent and professional photographer. Just make sure you have the hood attached in the “hood” position, rather than in the inverted stowed position that should only be used when you put the lens back in your camera bag.