Electronic Shutter versus Global Shutter


Today’s Question: For cameras that have an electronic shutter mode available wouldn’t you get the same benefit as from a “global shutter”? I would think in this mode the sensor would not be read row by row, or if it is that it would be so fast as to not be relevant.

Tim’s Quick Answer: An electronic shutter would not provide the benefits of a global shutter, and in fact in many cases an electronic shutter represents a disadvantage compared to a mechanical shutter.

More Detail: In a previous answer I addressed the concept of a global shutter, which is an image sensor that can read the data from the entire sensor at once, rather than reading that data line by line. The line-by-line readout can result in a rolling shutter distortion effect when photographing fast-moving subjects.

An electronic shutter is a feature of some cameras where you can shoot silently because the mechanical shutter doesn’t need to be activated. Instead of using the mechanical shutter to control how long the sensor is exposed to the light passing through the lens, the image sensor controls exposure by turning the photosites on and off.

With an electronic shutter the speed at which the camera can read data from the sensor determines the limitations of the electronic shutter. By contrast, with a mechanical shutter the sensor can activate photosites on the sensor before the shutter starts moving and can deactivate the photosites after the shutter has closed, because the shutter itself controls the flow of light to the sensor.

When a mechanical shutter isn’t in use the electronic shutter can therefore result in a greater rolling shutter effect than would have been present when using the mechanical shutter. Therefore, when photographing particularly fast-moving subjects it is generally better to use the mechanical shutter rather than the electronic shutter option.

Of course, as cameras continue to get faster and faster the risk of the rolling shutter effect is reduced. But as noted previously, the only way to eliminate the risk of a rolling shutter effect is to use a camera that features a global shutter, such as the new Sony a9 III (https://bhpho.to/3FP2f3B).

History State for Reference View


Today’s Question: Can the reference image [in the Develop module in Lightroom Classic] be a prior version in the history list?

Tim’s Quick Answer: Yes, if you use a virtual copy to represent the prior history state for the image.

More Detail: As noted in my answer from November 8th (https://asktimgrey.com/2023/11/08/reference-view-for-optimizing), you can use the Reference View feature in Lightroom Classic to have a reference image displayed next to the image you’re working on in the Develop module. This enables you to apply adjustments based on a different image, such as when you want to match the overall look of one image for another image.

Any image can be used as a reference image in Lightroom Classic, by simply switching to the Reference View and dragging an image from the filmstrip on the bottom panel into the Reference image area.

If you want to use a specific history state for an image as the reference image, I suggest creating a virtual copy for this purpose. Start by selecting the image in the Develop module and selecting the applicable state in the History section on the left panel (or select a snapshot if you’ve created one). Then right-click on the image and choose “Create Virtual Copy” from the popup menu. The virtual copy will inherit the current settings for the image, so it will reflect the history state. You can then set the original image back to the latest history state at the top of the History section.

The virtual copy created based on a specific history state for an image can then be dragged into the Reference image area. This provides the effect of having a specific history state for an image for reference while working on another image in the Develop module.

Image Off Screen when Zoomed Out


Today’s Question: In Photoshop I have my preferences set to use the scroll wheel on the mouse to enlarge or decrease the size. Enlarging isn’t an issue it is decreasing the size. The image slides off the screen or to somewhere other than the center. Is there a check box in preferences to set this so the image stays centered?

Tim’s Quick Answer: You can avoid this behavior when zooming out in Photoshop by turning off the Overscroll checkbox on the Tools tab of the Preferences dialog.

More Detail: When you use the scroll wheel or gesture to zoom in on an image in Photoshop, the area of the image that the mouse pointer is over is the area that will be the center of the zoomed in view. However, when you zoom out the image doesn’t get repositioned within the image area, so you might not be able to see the entirety of the image, for example.

However, if you turn off the Overscroll checkbox on the Tools tab of the Preferences dialog, you won’t be able to scroll the image beyond the bounds of the viewing area. That helps keep more of the image in view, because the entirety of the image is then not allowed to be moved outside the viewing area.

If you prefer using the mouse scroll wheel or gesture to zoom in or out, I suggest turning off the Overscroll checkbox, which will probably provide a solution you’re happy with in this context. It is also worth keeping in mind that there are other ways to quickly zoom in or out to specific settings.

For example, you can double-click on the button for the Zoom tool on the toolbar to zoom to a 100% zoom setting, and you can double-click on the button for the Hand tool to zoom to the Fit Screen setting. You can also press Ctrl+0 (zero) on Windows or Command+0 (zero) on Macintosh to size the image to the Fit Screen setting after you’ve zoomed in on a portion of the image.

First Global Shutter on a Mirrorless Camera


Today’s Question: I just saw an announcement about a new Sony camera with a “global shutter”. They say it provides faster performance and no motion distortion, but what exactly is a “global shutter”?

Tim’s Quick Answer: A global shutter records data for the entire image sensor simultaneously, rather than row by row as is common with a rolling shutter. A global shutter prevents various distortion issues, such as motion distortion or flash distortion. The new Sony a9 III (https://bhpho.to/3FP2f3B) is the first mirrorless camera to feature a global shutter.

More Detail: Many digital cameras use a rolling shutter, in which image data is not gathered all at once. Instead, with a rolling shutter the image data will be captured by the image sensor row by row or column by column. While the data for the full sensor is read quickly, it isn’t read simultaneously, which can lead to problems with fast-moving subjects.

For example, if you photograph a propeller-driven airplane or helicopter, with a rolling shutter the blades can be significantly distorted because the blade was moving faster than the data was being read from the sensor. Similarly, flash photography can be a challenge with a rolling sensor, leading to issues where for example the top part of the photo might reflect the flash illumination while the bottom half is extremely dark.

A global shutter prevents these issues because all sensor data is recorded simultaneously. This provides exceptional performance with high-speed subjects and other challenging scenarios. The Sony a9 III (https://bhpho.to/3FP2f3B), for example, is capable of continuously shooting raw captures at 120 frames per second, and supports flash synchronization all the way up to the maximum shutter speed of 1/80,000th of a second.

Reference View for Optimizing


Today’s Question: Your answer on Monday referred to preserving a version of an image for “reference”, and this reminded me of the existence of the Reference View in the Develop module [in Lightroom Classic]. Can you explain how this view option should be used?

Tim’s Quick Answer: Reference View in Lightroom Classic enables you to view two photos at once while working in the Develop module. The two images are the active image you are currently working on and the reference image that you want to review to make decisions about the adjustments you apply to the active image.

More Detail: Normally when working in the Develop module you are simply seeing the image you’re working on in the image preview area. From time to time, you might also use one of the “before and after” view options to get context for the adjustments you’ve applied to the current image. However, it can also be helpful to use Reference View so you can refer to one image while working on another.

To get started with Reference View in the Develop module click the Reference View button, which is the second button on the toolbar below the image preview area. You can click the button again to switch between having the two images arranged horizontally or vertically.

You can then drag the thumbnail for the image you want to reference from the filmstrip on the bottom panel to the Reference image area, which will be on the left or top of the image preview area depending on which orientation option you’ve selected. You can then click on the thumbnail of the image you want to optimize, with the ability to refer to the Reference image.

If you lock the Reference image with the padlock control on the toolbar below the image preview area, then the Reference image will remain in place even if you switch modules. If this option is unlocked, switching to another module and then back to the Develop module will cause the Reference image to be blank again.

Pixels versus Photosites


Today’s Question: It is my understanding that pixels are not the same as photosites where each photosite records one color [on a digital camera sensor]. The digital to analog converter creates pixels. What’s the real story?

Tim’s Quick Answer: This is mostly a matter of semantics. While the term photosite refers to a physical component of an image sensor, it is extremely common to refer to photosites as pixels even though pixels are elements of a digital image.

More Detail: The term pixel was derived from “picture element” and is used to describe the smallest element of a raster-based image (as opposed to a vector-based image). A pixel is therefore a component of a digital image, and a digital image often contains many (often millions) of pixels.

Technically speaking the individual elements on an image sensor are photosites, not pixels. Those photosites contain hardware that converts light energy into a discreet digital value that then gets processed into the values that define pixels in the resulting digital image.

It is also true that digital cameras only record a single color for each photosite, because those photosites aren’t actually recording color but rather light intensity based on light that has been filtered for color. Even sensors that capture full color for each pixel, such as the Foveon X3 sensor, only capture one color per photosite. In the case of the Foveon sensor there are simply three photosites on the image sensor corresponding to each pixel in the final image.

In common usage, the photosites on an image sensor are often referred to as pixels. For example, most digital camera marketing materials describe resolution in megapixels (millions of pixels) since the images captured with that sensor will contain the number of pixels referenced. But we tend to think of the image sensor as having a particular number of megapixels, which contributes to the photosites being referred to as pixels.

In my earlier days I was more pedantic about this issue, and would use the term “photosite” when referring to an image sensor and “pixel” to refer to a digital image. I’ve since decided to conform with the more common use of the term pixel when talking about photosites. I similarly stopped using all capital letters when talking about raw captures, since raw in this context is not an acronym, even though I liked using all caps for raw so that it stood out like the other acronyms and initialisms used for other file formats. And yes, I do differentiate between acronyms and initialisms, even though I no longer tend to differentiate in the same way between photosites and pixels.

By the way, I also find it amusing that photosite is the technical name for what amounts to a pixel on an image sensor, but my spell checker doesn’t think photosite is really a word.

Process Version Workflow


Today’s Question: Is it a reasonable workflow alternative with an image previously processed in an older Lightroom Development version to export a duplicate, remove all processing and reprocess with the new Develop module?

Tim’s Quick Answer: I would suggest simply creating a virtual copy rather than creating a duplicate of the original image file. You can then use updated settings for either the original image or the virtual copy, preserving the original look based on the older process version.

More Detail: Today’s question is a follow-up from a couple of questions about process versions in Lightroom Classic that I addressed recently. A process version basically represents a particular version of Lightroom Classic in the context of the Develop module. To take advantage of all the latest features and adjustment updates, you need to be working with the latest process version, which can be viewed and changed in the Calibration section of the right panel in the Develop module..

However, if you change the process version for a photo it is possible (or even likely) that the appearance of the photo may change. It can therefore be a good idea to preserve the appearance based on the existing process version before updating to a new process version.

As suggested in today’s question, you could certainly create a duplicate copy of the original image, such as by exporting a copy and adding that copy to the Lightroom Classic catalog. However, you can also easily accomplish this by using a virtual copy.

For example, you could right-click on an image that is set to an older process version and choose “Create Virtual Copy” from the popup menu. You could then update the process version for just one of those images. In this case I would probably keep the old process version set for the virtual copy, and update the process version for the original image.

You could then update the adjustment settings for the image you updated the virtual copy for, even going so far as to click the Reset button at the bottom of the right panel in the Develop module to reset all adjustments to their defaults. But the point is that you can refine the overall adjustments based on the latest process version, while preserving the previous version of the image with an older process version for your reference.

Raw Captures with Full Color


Today’s Question: In your answer about TIFF versus raw captures you said that “most raw captures don’t contain full color information for each pixel”. Wouldn’t this be true of all raw captures since that’s what makes a raw capture “raw”?

Tim’s Quick Answer: While most digital camera image sensors only capture a single color for each pixel, not all sensors have this limit. For example, the Foveon X3 sensor captures full color for each pixel.

More Detail: Most camera image sensors use a Bayer pattern array, where out of every four pixels two record green light, one records red light, and one records blue light. Other image sensors use a variation on this concept. But most only record one color value (red, green, or blue) for each pixel. Software then processes this information to calculate the “missing” color values for each pixel to generate the full-color image.

This issue is generally referred to as the image being mosaiced, meaning it contains a mosaic of different values that don’t represent complete image data. This mosaiced attribute is what we generally consider to represent a raw capture.

However, there is at least one exception that has made it into production cameras. That exception is the Foveon X3 sensor, which uses a layered approach to record full color information for all pixels on the sensor.

While the technology and concept of the Foveon X3 sensor is impressive, that hasn’t translated into wide adoption. The company that created the Foveon sensor was acquired by Sigma a number of years ago, and the sensor has only been available in Sigma cameras. The Sigma cameras haven’t seen wide adoption.

So, the vast majority of cameras don’t capture full color information for all pixels, but there are exceptions.

File Size versus Print Size


Today’s Question: If a TIFF file is much larger [compared to a raw capture], does that mean you can also print much larger without any loss of resolution?

Tim’s Quick Answer: No, because the file size of a TIFF is not due to greater resolution, but rather due to the nature of the file.

More Detail: Today’s question was a follow-up to a prior question about the large size of a TIFF file created by sending a raw capture to Photoshop from Lightroom Classic. As I explained in my answer to that question, a TIFF file created from a raw capture will generally be about three times larger than the original capture.

While an image with greater resolution will have a larger file size, that doesn’t mean that a larger file size automatically means there is greater resolution in the image. In other words, just because an image has a larger file size doesn’t always mean it can be printed at a larger size with equal quality compared to an image with a smaller file size.

In the case of a raw capture compared to a TIFF file, the reason the raw capture generally has a file size that is one-third the size of the TIFF image is that most raw captures don’t contain full color information for each pixel. Rather, in most cases each pixel will only have a value for either red, green, or blue, not all three. Because a TIFF file would have all three color values for every pixel, the file will be about three times the size.

Similarly, if you had added additional image layers to an image in Photoshop, such as when creating a composite image, the file size would be larger but the image couldn’t be printed any larger without degrading quality.

Another example going in the other direction would involve saving an image as a JPEG file. Even though the file size would be significantly smaller, the image could still be printed at about the same size as the source image, with the caveat that the print quality would be degraded at least slightly based on the JPEG compression.

Ultimately what determines how large an image can be printed with good quality is the resolution of the image, meaning the total number of pixels in the image. While a raw capture generally doesn’t contain full color information for each pixel, it can still be thought of as having the full resolution represented by the image sensor. The raw capture just needs to be processed to generate the full color information for all pixels.

Unwanted Icon on Layer Mask


Today’s Question: Enlarging the thumbnails on the Layers panel in Photoshop made it easier to see the layers and layer masks, but there is still a small intrusive thumbnail appearing on the mask. I was hoping to get rid of the layer mask icon altogether, but I guess this isn’t an option?

Tim’s Quick Answer: The new badge that appears at the bottom-right corner of layer masks in Photoshop is a new feature of Photoshop version 25.1. The public beta version of Photoshop includes an option to remove the badges.

More Detail: Today’s question is a follow-up to Monday’s question, where I addressed the option to enlarge the thumbnails for layers and layer masks on the Layers panel in Photoshop. However, with the latest update to version 25.1 of Photoshop there is a new badge feature that puts an icon on the layer mask for any layers that include a mask.

Several readers have reached out to me about this, as they find the badge gets in the way of evaluating a layer mask. I completely agree that the new badge icon isn’t all that helpful and can interfere with evaluating layer masks.

In Photoshop version 25.1 there isn’t an option to remove the badges on layer masks. However, there is such an option in the current public beta version of Photoshop. So, if you want to get rid of the badge icons you could either revert to an earlier version of Photoshop or use the public beta while we await an update to Photoshop that will include the option to remove the badge.

If you install the public beta version of Photoshop (via the “Beta apps” category on the Apps tab of the Creative Cloud application), you can click on the panel popup menu button at the top-right of the Layers panel and choose “Panel Options” to bring up the Layers Panel Options dialog. There you’ll find a “Show layer mask badges” checkbox that you can turn off to remove the badges on layer masks.

I would assume that this option in the public beta will soon be available in an update to the production version of Photoshop soon. At least I hope so, because I certainly don’t think the badges on layer masks provide a benefit, and I suggest disabling them.