I've seen quite a few comments lately bemoaning the additional processing time that the Nexus' HDR+ mode requires, and it seems that there might not be a lot of understanding as to what goes on behind the ol' curtain, particularly since most other phones require little to no extra effort when you flip on HDR.
*inhale*
As you can tell by the name, HDR+ is a bit more than what most people understand HDR to be, and I'll get to the '+' part in a little bit. But backing up a bit, HDR is High Dynamic Range photography. Camera sensors are not nearly as powerful as those perched on the front of the human head, and when faced with scenes with large variations in brightness, either the dark bits or the bright bits often suffer.
Photographers have an array of tricks up their sleeves to help fix things, mostly involving staging the shot, taking several photographs of varying exposures (called 'exposure bracketing') and then merging those different exposures with a graphical editing program like Photoshop or Lightroom. Sometimes, it is just to clean up over and underexposed parts of the image and other times to create an extremely stylized final product.
Now, phones happen to have extremely powerful processors in them, miniaturized supercomputers capable of incredible feats of digital strength. So phone manufacturers now include 'HDR' modes with their camera software. The camera apps do much of the same work that a photographer would do... taking multiple pictures of varying exposures then stitch them together and then process the final image, just like non-HDR exposures, to reduce noise and touch up parts of the image that might have some digital crapola left over.
One day, some engineers over at Google decided to go about things a little differently... could there be a better way of processing these images? I have my own theories how this came about. Google has been working with NASA quite a bit lately and I wonder if one of their engineers talked to a few astronomers one morning and had an epiphany....
Astronomers often face an uphill battle with their telescopes, particularly the ground based ones that do most of the grunt work. They are forced to point extremely sensitive optical sensors through 100+ miles of churning atmosphere to view an object millions (or billions) of light years away, trying to view details that are close to resolving limits of the telescope.
Before the age of digital photography, the secrets of deep space were hidden behind the blurry fog of our planet's atmosphere. Now, astronomers use several technological tricks to try to get a better image and one involves taking a bunch of quick exposures and choosing the 'best' of the exposures as the starting point (known as lucky imaging) then averaging out the image using the information in the other exposures (the appropriately named 'noise reduction by image averaging').
So they can a single picture like this:
And (with a bunch more exposures) turn it into something that looks like this:
So, why can't phones use the same process? So here is how HDR+ was born. When you tap that shutter button, the camera goes off and snaps off a series of quick exposures using the same settings (it does not use exposure bracketing). And I suspect that the number of exposures varies on the available light. That little spinning circle animation gives you something to look at while it does its thing. Obviously, the shorter each exposure is, the shorter the overall exposure time. Using HDR+ in the daylight will be near instant where in dark scenes, it could take a beat or two extra. Then it's all up to the processing.... it picks the image with the best overall characteristics (so if there's a little bit of movement during the overall exposure, you're OK), then starts to average each of the 12.3 million pixels to come up with the final image.
This is why the processing takes so long... that's a lot of pixels to sort through. But it's also its biggest advantage. I've posted these shots before, but it illustrates how well HDR+ works. The top image is a 100% crop HDR shot taken from a Samsung Galaxy S7, the bottom, an HDR+ shot from a Nexus 6P.
S7:
Now the 6P:
The difference in post processing between 'traditional' HDR and HDR+ processing should stand out. On the S7, you see a lot of digital artifacts... details are kind of chopped up a bit, colors muted. Look at at the Travelocity Gnome's face, the colors in the portrait of me and my wife, the details in the photograph of my son waving the flag, the curve of the vase. The white background in the S7 has a bit of digital smudge where the Nexus' has what I would consider something more akin to the grain you see in a film camera.
The S7's HDR processing hacks up the picture a bit because it is going through and artificially reducing noise and sharpening the picture algorithmically. Whereas the HDR+ shot is using information from the actual scene itself, retaining the information in the actual image, rather than processing it away. If you look at the two main images from above on a phone, the HDR+ image might not immediately appear to the eye as crisp, but it still retains the depth of the picture.... I kind of equate it as the difference between analog and digital audio.
*exhale*
So I hope this all makes sense. HDR+ is a killer feature, and in pretty much every condition leads to some spectacular results. I use it almost exclusively and only occasionally have to drop out to the standard mode to get the picture I want.
If you want to learn more, there's an excellent Google blog post here... and a good one about using multiple exposure averging here
*inhale*
As you can tell by the name, HDR+ is a bit more than what most people understand HDR to be, and I'll get to the '+' part in a little bit. But backing up a bit, HDR is High Dynamic Range photography. Camera sensors are not nearly as powerful as those perched on the front of the human head, and when faced with scenes with large variations in brightness, either the dark bits or the bright bits often suffer.
Photographers have an array of tricks up their sleeves to help fix things, mostly involving staging the shot, taking several photographs of varying exposures (called 'exposure bracketing') and then merging those different exposures with a graphical editing program like Photoshop or Lightroom. Sometimes, it is just to clean up over and underexposed parts of the image and other times to create an extremely stylized final product.
Now, phones happen to have extremely powerful processors in them, miniaturized supercomputers capable of incredible feats of digital strength. So phone manufacturers now include 'HDR' modes with their camera software. The camera apps do much of the same work that a photographer would do... taking multiple pictures of varying exposures then stitch them together and then process the final image, just like non-HDR exposures, to reduce noise and touch up parts of the image that might have some digital crapola left over.
One day, some engineers over at Google decided to go about things a little differently... could there be a better way of processing these images? I have my own theories how this came about. Google has been working with NASA quite a bit lately and I wonder if one of their engineers talked to a few astronomers one morning and had an epiphany....
Astronomers often face an uphill battle with their telescopes, particularly the ground based ones that do most of the grunt work. They are forced to point extremely sensitive optical sensors through 100+ miles of churning atmosphere to view an object millions (or billions) of light years away, trying to view details that are close to resolving limits of the telescope.
Before the age of digital photography, the secrets of deep space were hidden behind the blurry fog of our planet's atmosphere. Now, astronomers use several technological tricks to try to get a better image and one involves taking a bunch of quick exposures and choosing the 'best' of the exposures as the starting point (known as lucky imaging) then averaging out the image using the information in the other exposures (the appropriately named 'noise reduction by image averaging').
So they can a single picture like this:
And (with a bunch more exposures) turn it into something that looks like this:
So, why can't phones use the same process? So here is how HDR+ was born. When you tap that shutter button, the camera goes off and snaps off a series of quick exposures using the same settings (it does not use exposure bracketing). And I suspect that the number of exposures varies on the available light. That little spinning circle animation gives you something to look at while it does its thing. Obviously, the shorter each exposure is, the shorter the overall exposure time. Using HDR+ in the daylight will be near instant where in dark scenes, it could take a beat or two extra. Then it's all up to the processing.... it picks the image with the best overall characteristics (so if there's a little bit of movement during the overall exposure, you're OK), then starts to average each of the 12.3 million pixels to come up with the final image.
This is why the processing takes so long... that's a lot of pixels to sort through. But it's also its biggest advantage. I've posted these shots before, but it illustrates how well HDR+ works. The top image is a 100% crop HDR shot taken from a Samsung Galaxy S7, the bottom, an HDR+ shot from a Nexus 6P.
S7:
Now the 6P:
The difference in post processing between 'traditional' HDR and HDR+ processing should stand out. On the S7, you see a lot of digital artifacts... details are kind of chopped up a bit, colors muted. Look at at the Travelocity Gnome's face, the colors in the portrait of me and my wife, the details in the photograph of my son waving the flag, the curve of the vase. The white background in the S7 has a bit of digital smudge where the Nexus' has what I would consider something more akin to the grain you see in a film camera.
The S7's HDR processing hacks up the picture a bit because it is going through and artificially reducing noise and sharpening the picture algorithmically. Whereas the HDR+ shot is using information from the actual scene itself, retaining the information in the actual image, rather than processing it away. If you look at the two main images from above on a phone, the HDR+ image might not immediately appear to the eye as crisp, but it still retains the depth of the picture.... I kind of equate it as the difference between analog and digital audio.
*exhale*
So I hope this all makes sense. HDR+ is a killer feature, and in pretty much every condition leads to some spectacular results. I use it almost exclusively and only occasionally have to drop out to the standard mode to get the picture I want.
If you want to learn more, there's an excellent Google blog post here... and a good one about using multiple exposure averging here
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