May the Alpha 7S III be Utilizing the Identical Sensor because the Alpha 1?

A teardown by astrophotography web site LandingField discovered that the 12-megapixel Alpha 7S III is utilizing 4 photosites to create a single pixel, which means its precise decision is 48-megapixels. Some have taken this to imply that it makes use of the identical sensor because the Alpha 1.

After tearing down the sensor and inspecting it underneath a microscope, Landingfield found that the sensor makes use of what the publication describes as a “2×2 binning” design, which results in the conclusion that the sensor within the digital camera — the IMX510 — really has a 48-megapixel native decision.

The RGGB Bayer sample is unfold throughout a 4×4 grid. After sensor readout, the 4 pixels in every of the identical coloration are then mixed digitally to present one pixel earlier than sending out on the SLVS-EC interface. This might clarify the rise in learn noise. From my data, none of Sony DSLR CIS helps cost binning resulting from limitation in its pixel structure. By combining 4 pixels digitally, you’d improve the noise variance by 4 and therefore learn noise nearly doubles (sqrt to RMS).

This assertion brings up a serious query: would what is going on right here be binning or oversampling? “Pixel binning” is described as utilizing a set of adjoining pixels to create a single pixel whereas oversampling is described as utilizing a number of full-size pixels to create one bigger pixel. It appears like semantics, however Sony really particularly writes that the Alpha 7S III doesn’t have pixel binning in its press supplies during the launch of the camera, which means the accusation of binning is fairly important.

IMX510 (high) 2×2 binning pixel underneath a 50x goal microscope. | LandingField
FSI single pixel in IMX235 underneath a 50x goal microscope. | LandingField

Particularly, Sony definitively said that the Sony Alpha 7S Mark III has no pixel binning or line skipping. Sony’s authorized staff can be unlikely to green-light this assertion if the digital camera did the truth is really pixel bin. It’d come right down to what Sony’s engineers outline as “binning” or “oversampling.”

PetaPixel reached out to Sony, however the firm didn’t instantly reply. As a rule, nonetheless, Sony doesn’t present data on its engineering designs, so it’s unlikely the reply to those questions would come from the corporate direclty.

Few specialists on sensor engineering exist exterior of those that work for the digital camera firms, however Imaging Resource’s founder Dave Etchells is one in all them. PetaPixel requested him to supply a few of his ideas on the subject.

“It’s binning however in a special sense than what folks have conventionally referred to as binning,” he tells PetaPixel after looking at LandingField’s report. “It’s binning digitally which is totally different than oversampling as nicely. Usually once we say binning that implies that they’re taking the precise cost that’s collected by every pixel and mixing it to a bigger cost earlier than studying it out [which isn’t happening here].”

Etchells says that a technique to consider that is to consider the person pixels as cups of water and the capacitor as a bigger cup — rudimentary, however illustrative. With binning, consider these cups of water as being dumped into the bigger cup after which measured. What Sony is doing right here is as a substitute of that, the cups are being individually measured and never dumped into a bigger cup in any respect.

“What Sony seems to be doing on this sensor is that they measure every of the little ‘cups’ after which provides these numbers collectively. So the cost is combining the numbers as it’s being learn out,” he says.

“Sony is studying the voltage on every particular person capacitor and including the numbers collectively. So it’s not technically binning. It has the identical decision penalties the way in which binning does, however you additionally really get a worse signal-to-noise ratio than should you did bin,” he explains.

Wanting again on the cups analogy, Etchells says it’s form of like studying imagining that there are measurement strains on every of the person cups and that there’s some degree of inaccuracy related to these strains if somebody have been to eyeball pouring liquid into these cups to measure them. Whether or not these strains are on every small cup or on the bigger cup, there’s some degree of uncertainty in studying it. If somebody was to dump all of the liquid of the small cups into one massive cup after which learn it, there can be only one quantity of error. However in case you have 4 little cups which are being measured individually as a substitute, that’s 4 doable errors which are being mixed collectively.

“Sony isn’t binning within the conventional sense, however they’re taking the alerts out of a bunch of 4 pixels and measuring them and mixing these collectively earlier than they get despatched on to the processor. It’s the identical as binning from the standpoint that you simply’re shedding decision, nevertheless it’s totally different from binning in that you simply’re most likely additionally getting extra noise,” Etchells says. “They’re combining 4 particular person measurements of pixel voltage and that mainly means you have got twice as a lot readout noise.”

Some have taken the construction of the sensor to imply that Sony used the identical sensor — or some derivation of it — within the Alpha 7S III because it did within the Alpha 1, for the reason that Alpha 1 gives full-width 4K video seize with pixel binning from 48 million photosites. If Landingfield’s data is right, that is what was discovered on the Alpha 7S III, however the binning is as a substitute hard-wired into the sensor.

Etchells says this does make some sense, as it could be a comparatively minor change to regulate how the corporate was studying a sensor versus designing solely new pixels and would clarify why the corporate went with a route that really launched extra noise than conventional pixel binning would. That is additionally one principle that LandingField’s report involves as to why Sony would go along with this design.

The opposite principle as to why Sony would do that is that for HDR, there’s doubtlessly a very massive benefit in that every pixel can have totally different sensitivities. By various the sensitivity on every pixel it could give them extra dynamic vary, in principle, Etchells says.

Each the Alpha 1 and the Alpha 7S III have 759 phase-detection autofocus factors, which can lend credence to the concept each use variations of the identical sensor. However on the flipside, 4 pixels making up one pixel within the 12-megapixel Alpha 7S III would imply 48-megapixels, which is fewer than the Alpha 1’s 50-megapixels. That might imply the sensors are totally different, however one may argue that Sony may simply be cropping the Alpha 7S III sensor a bit.

So are each cameras utilizing variations on the identical sensor? In all probability not, nevertheless it’s inconclusive with out extra data.

“Based mostly on the recorded pixel pitch (Alpha 7S III is 8.4 versus the Alpha 1’s 4.16), There’s a few 2% distinction and so I strongly suspect they’re not the identical chip because it’s not precisely divisible into one another. However that relies on if we’re taking a look at precise pixel dimensions printed by Sony or if we’re simply dividing sensor dimension by the variety of pixels,” Etchells continues.

He additionally says that is assuming that the 2 cameras have precisely the identical framing.

“If it seems that the Alpha 7S III is cropped simply barely tighter, I’d then argue strongly that it was the identical chip. It might be attention-grabbing to have each cameras locked down with the identical lens to see the place the sides of the body can be.”

The complete breakdown of the sensor could be seen on LandingField, which it ought to be famous by no means particularly asserts that the sensor shares something in frequent with the Alpha 1. Nonetheless, it’s price contemplating what the corporate defines as pixel binning or oversampling and fascinated with what this implies so far as sensor growth.

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