Persianimmortal
Screenwriter
Screencaps have been the subject of much discussion within a range of threads, most recently the Spartacus thread, where it was suggested that a separate thread be created for the topic. Since I'm not one of the major participants in the debate for either side, I thought my status as a relatively neutral party would allow me to create this thread so that the topic can be discussed rationally here without continually derailing other threads.
First, a little in the way of background information to bring everyone up to speed:
Screencaps 101
Screencap is short for screen capture (also called screenshot), which is actually a bit of a misnomer, since a proper screencap is not taken from a screen, such as by photographing an image on a TV. To be of any real use, a screencap needs to be a capture of graphics data directly from a Blu-ray disc. This is done using a computer which has a Blu-ray drive, through Blu-ray playback software. Importantly, the software must specifically be set not to rescale or filter the image in any way.
The captured data needs to be saved in a particular digital image format, such as BMP, PNG or JPG. Each image format has a certain level of compression applied to its data to reduce file size. The greater the compression applied to a particular image format, the less the resulting image will represent the actual Blu-ray data from which it was taken; small glitches - known as artifacts - will be introduced into the image and/or any existing faults or characteristics of the image will be exaggerated. The JPEG format for example is known as a "lossy" format, because its compression algorithm removes certain data to achieve relatively small file sizes. For more faithful reproduction of digital images, a "lossless" format, such as PNG, is preferred.
The bottom line is that a screencap, if taken correctly, should show exactly the same image as if you had the actual Blu-ray disc playing on your display, paused at the relevant scene. That's because the underlying data should be approximately the same.
There's also the issue of the way the images are viewed. All screencaps are viewed through a display device, typically a computer monitor. If the display is not instrument calibrated to the Rec.709 standard, then the image seen on the screen will not be an accurate reflection of the data. Using an uncalibrated monitor or TV will mean that a screencap will appear to the viewer as being too dark or too bright, excessively sharp or blurred, or overly saturated or undersaturated based on its settings, rather than what's contained in the actual image.
An Example
To kick off the discussion, I want to demonstrate some of the pros and cons of screencaps using one of the more controversial recent Blu-rays: The Man Who Knew Too Much (1956).
Robert Harris, in his Review of The Man Who Knew Too Much, gave this disc a 2/5 for image quality, and concludes that the title needs to be recalled, due in particular to color pulsing visible throughout the film. Similarly, Kevin HK, in his Review of the Hitchcock Collection, gives the BD a 0.5/5 score for image quality and also notes that a recall and restoration is required.
Below are four screencaps I've taken directly from my BD of The Man Who Knew Too Much. Each image is shown as a thumbnail, which must be clicked to see the full 1920x1080 PNG image:
These help to highlight several issues regarding the use of screencaps:
The first screencap is a bit blurry, and if taken out of context, could be used to argue that the Blu-ray is actually not a major step up from the DVD version. This happens quite frequently. Depending upon the scene being capped, the use of optical effects, front projection, or other techniques or filmic restrictions may result in particular scenes looking relatively poor, and thus used as ammunition to bring down a transfer.
The second screencap, while not perfect, reveals better detail and natural colors, and also shows the grain structure. It is generally more indicative of how the film actually looks for the most part.
But the third and fourth screencaps are interesting, and quite important. They're taken only seconds apart, and if you download both of them in full 1080p size, then flick between the two rapidly, you'll clearly see that they show completely different levels of color density in the same scene. Look in particular at the tone of the faces, and the hills in the background. This is because when in motion, that actual section of the movie - indeed whole stretches - show strong color pulsing. If only one of these screencaps was provided, you would either think the film was slightly oversaturated, or less so, and in either case, you would not know anything about the color pulsing just by looking at screencaps taken from any part of the movie. This is a major drawback of screencaps: they cannot show what a movie is like in motion, which is of course how a film is usually watched.
Given the color pulsing is a critical issue, and the main reason behind RAH and Kevin's low review scores, it's very important to see that screencaps would be highly misleading in the case of The Man Who Knew Too Much.
On the positive side however, the screencaps can help to show people that the image quality of this disc may actually be acceptable to their eyes, despite the very low review scores - as long as the strong color pulsing is explicitly kept in mind. In other words, the screencaps - when combined with an appropriately knowledgeable review - can help consumers make purchasing decisions based on their particular tastes. Perception of image is after all largely subjective.
Another critical issue, which is definitely not subjective, is whether the movie looks the way it's supposed to. Unless you have explicit knowledge of such things, no amount of screencaps call tell you whether the Blu-ray is faithful to the original look of the movie, or whether it has been altered in some way. Once again, all too frequently people make judgements regarding how good or bad a movie looks without knowing whether any faults are inherent to the actual original film, or conversely, whether it has been artificially improved to look more aesthetically pleasing at the cost of fidelity to source.
With this little primer in mind, I'd be interested to hear more of the pros and cons of screencaps from forum members.
First, a little in the way of background information to bring everyone up to speed:
Screencaps 101
Screencap is short for screen capture (also called screenshot), which is actually a bit of a misnomer, since a proper screencap is not taken from a screen, such as by photographing an image on a TV. To be of any real use, a screencap needs to be a capture of graphics data directly from a Blu-ray disc. This is done using a computer which has a Blu-ray drive, through Blu-ray playback software. Importantly, the software must specifically be set not to rescale or filter the image in any way.
The captured data needs to be saved in a particular digital image format, such as BMP, PNG or JPG. Each image format has a certain level of compression applied to its data to reduce file size. The greater the compression applied to a particular image format, the less the resulting image will represent the actual Blu-ray data from which it was taken; small glitches - known as artifacts - will be introduced into the image and/or any existing faults or characteristics of the image will be exaggerated. The JPEG format for example is known as a "lossy" format, because its compression algorithm removes certain data to achieve relatively small file sizes. For more faithful reproduction of digital images, a "lossless" format, such as PNG, is preferred.
The bottom line is that a screencap, if taken correctly, should show exactly the same image as if you had the actual Blu-ray disc playing on your display, paused at the relevant scene. That's because the underlying data should be approximately the same.
There's also the issue of the way the images are viewed. All screencaps are viewed through a display device, typically a computer monitor. If the display is not instrument calibrated to the Rec.709 standard, then the image seen on the screen will not be an accurate reflection of the data. Using an uncalibrated monitor or TV will mean that a screencap will appear to the viewer as being too dark or too bright, excessively sharp or blurred, or overly saturated or undersaturated based on its settings, rather than what's contained in the actual image.
An Example
To kick off the discussion, I want to demonstrate some of the pros and cons of screencaps using one of the more controversial recent Blu-rays: The Man Who Knew Too Much (1956).
Robert Harris, in his Review of The Man Who Knew Too Much, gave this disc a 2/5 for image quality, and concludes that the title needs to be recalled, due in particular to color pulsing visible throughout the film. Similarly, Kevin HK, in his Review of the Hitchcock Collection, gives the BD a 0.5/5 score for image quality and also notes that a recall and restoration is required.
Below are four screencaps I've taken directly from my BD of The Man Who Knew Too Much. Each image is shown as a thumbnail, which must be clicked to see the full 1920x1080 PNG image:
These help to highlight several issues regarding the use of screencaps:
The first screencap is a bit blurry, and if taken out of context, could be used to argue that the Blu-ray is actually not a major step up from the DVD version. This happens quite frequently. Depending upon the scene being capped, the use of optical effects, front projection, or other techniques or filmic restrictions may result in particular scenes looking relatively poor, and thus used as ammunition to bring down a transfer.
The second screencap, while not perfect, reveals better detail and natural colors, and also shows the grain structure. It is generally more indicative of how the film actually looks for the most part.
But the third and fourth screencaps are interesting, and quite important. They're taken only seconds apart, and if you download both of them in full 1080p size, then flick between the two rapidly, you'll clearly see that they show completely different levels of color density in the same scene. Look in particular at the tone of the faces, and the hills in the background. This is because when in motion, that actual section of the movie - indeed whole stretches - show strong color pulsing. If only one of these screencaps was provided, you would either think the film was slightly oversaturated, or less so, and in either case, you would not know anything about the color pulsing just by looking at screencaps taken from any part of the movie. This is a major drawback of screencaps: they cannot show what a movie is like in motion, which is of course how a film is usually watched.
Given the color pulsing is a critical issue, and the main reason behind RAH and Kevin's low review scores, it's very important to see that screencaps would be highly misleading in the case of The Man Who Knew Too Much.
On the positive side however, the screencaps can help to show people that the image quality of this disc may actually be acceptable to their eyes, despite the very low review scores - as long as the strong color pulsing is explicitly kept in mind. In other words, the screencaps - when combined with an appropriately knowledgeable review - can help consumers make purchasing decisions based on their particular tastes. Perception of image is after all largely subjective.
Another critical issue, which is definitely not subjective, is whether the movie looks the way it's supposed to. Unless you have explicit knowledge of such things, no amount of screencaps call tell you whether the Blu-ray is faithful to the original look of the movie, or whether it has been altered in some way. Once again, all too frequently people make judgements regarding how good or bad a movie looks without knowing whether any faults are inherent to the actual original film, or conversely, whether it has been artificially improved to look more aesthetically pleasing at the cost of fidelity to source.
With this little primer in mind, I'd be interested to hear more of the pros and cons of screencaps from forum members.
