Do image sensors lose sensitivity?

couldabin · Oct 25, 2021

I bought a Sony Alpha 7 brand new several years ago, in part because it was the only full-frame digital I could afford. I was satisfied -- but not really overwhelmed -- by the image quality. Since then it seems the image quality has degraded. It's a bit like the frog in gradually warming water: I didn't notice it at the time but when I look back at images from 5 or 6 years ago, they seem far more vibrant. I have been considering investing in new lenses (buying an adapter so that it will accept Canon EF lenses) but don't want to go there is the sensor really is fading. Is this possible? If so, is there a remedy?

Moose22 · Oct 25, 2021

Is your sensor clean? Environmental contaminates can be a slightly oily haze, not just dust spots, and they might degrade quality some.

Some.

If it's dramatic it's something else and I'd get it looked at. I didn't think a sensor would fade all over. Usually they're good or you'll get hot pixels, but not just fade. I may be wrong on that.

At the very least you might get a good cleaning done or give it a try if you don't have a tech local you trust.

Nodda Duma · Oct 25, 2021

It is physically not possible for semiconductor based photo-detectors to lose sensitivity or fade.

MattKing · Oct 25, 2021

Software can play a huge role in this. If you are using different software - either the old software upgraded, or new, replacement software - than you were 5 or 6 years ago, than what you are observing is fairly likely to be related to that, rather than the sensor itself.

Oren Grad · Oct 25, 2021

Nodda Duma said:
It is physically not possible for semiconductor based photo-detectors to lose sensitivity or fade.

But it's possible in principle for the dyes/pigments in the color filter array to fade. Search the web and you'll find various discussions of this.

That said, I've never heard of a documented instance where the CFA on any modern digital camera has faded noticeably in ordinary use, let alone in a just a few years of routine amateur use. I too would guess that there's something else going on here.

Nodda Duma · Oct 26, 2021

I don’t need to search the web for devices that I work with at an engineering level every day.

I was very specific about my statement. Regarding fading of a bayer mask: While theoretically possible, I’ve never seen fading of a Bayer mask in extreme conditions such as space applications, or even after HALT (highly accelerated life cycle testing) to simulate 10-20 years of heavy use. In a practical sense, insufficient UV reaches the dyes over the lifetime of a camera to cause fading, being absorbed by the materials that make up the cover plate and optics in front of it. (how often do you go outside and point a sensor at a UV source?). Even if so, the symptoms wouldn’t be fading of the colors in the final image. It would result in color shifts towards magenta due to the demosaicing algorithm doing its job with what would then be incorrect scaling coefficients.

Bayer masks formed from dielectric coatings never fade.

I agree with others that most likely explanation is that there have been changes in the image processing software (Lightroom, etc) algorithms over the past few years. Adjust vibrancy/saturation of the new images to match your results from before.

couldabin · Oct 26, 2021

I'm obviously no expert and these questions undoubtedly underscore that ... but don't electronic components fail all the time? Is it possible that one or two or more pieces in the chain has failed, compromising the image? I have not changed/updated the software. FWIW, I am in the process of tracking down a photo service that will clean the sensor (since that hasn't been done, either).

faberryman · Oct 26, 2021

couldabin said:
I'm obviously no expert and these questions undoubtedly underscore that ... but don't electronic components fail all the time? Is it possible that one or two or more pieces in the chain has failed, compromising the image? I have not changed/updated the software. FWIW, I am in the process of tracking down a photo service that will clean the sensor (since that hasn't been done, either).

Anything is possible. I have never heard of a digital sensor failing in the way you described, but maybe I have lived a sheltered life and they fail every day. I have a couple of Canon Elphs from the turn of the century and they continue to provide the same image quality they always have, not that that is saying much. You might try posting your question on a digital camera website. The group of film enthusiasts around here is the least likely bunch of guys to have wide experience with digital cameras. You know that if you shoot film, you get a brand new sensor with every roll.

Here is a link to the Sony Alpha forum on dpreview.com. You might try typing "sensor failure" in the search box.

https://www.dpreview.com/forums/1064

Here's a link to a camera repair site specializing in Sony Alpha repairs. You might want to shoot them an email.

https://digitronav.com/repair/camcorder-repair/sony-alpha-repair/

couldabin · Oct 26, 2021

faberryman said:
Anything is possible. I have never heard of a digital sensor failing, but maybe I have lived a sheltered life and they fail every day. I have a couple of Canon Elphs from the turn of the century and they continue to provide the same quality of images they always have, not that that is saying much. You might try posting your question on a digital camera website. The group of film enthusiasts around here is the least likely bunch of guys to have wide experience with digital cameras. You know that if you shoot film, you get a brand new sensor with every roll.

Here is a link to the Sony Alpha forum on dpreview.com. You might try typing "sensor failure" in the search box.

https://www.dpreview.com/forums/1064

Here's a link to a camera repair site specializing in Sony Alpha repairs. You might want to shoot them an email.

https://digitronav.com/repair/camcorder-repair/sony-alpha-repair/

Thanks for these links!

ced · Oct 26, 2021

Wonder if you hang around with your camera while someone smokes a vape, you will be surprised how much gunk is floating around & penetrating everything.
At home I see this stuff deposit on laptop screens etc & are near impossible to get cleaned properly even with good window cleaners. As another pointed out check to see if your sensor needs attention.

Pieter12 · Oct 26, 2021

ced said:
Wonder if you hang around with your camera while someone smokes a vape, you will be surprised how much gunk is floating around & penetrating everything.
At home I see this stuff deposit on laptop screens etc & are near impossible to get cleaned properly even with good window cleaners. As another pointed out check to see if your sensor needs attention.

I m not familair iwth this camera, but with a lens mounted, it would seem pretty hard for vaping or other substances to deposit on the sensor evenly enough to deteriorate the entire surface, even over a long period of time. Dust particles can certainly land on the sensor during a lens change, and Leica did have a major issue with the detioration of the cover glass on their CCD sensors, but it was in spots, not the entire snesor area.

mmerig · Oct 26, 2021

Nodda Duma said:
It is physically not possible for semiconductor based photo-detectors to lose sensitivity or fade.

Are the devices current biased? If that's too high, it could break them, or perhaps weaken them. But I don't think that is happening. There may be hardware problems downstream of the sensor, if and where the signal is amplified. For example, capacitors, especially surface-mounted ones, can degrade and cause power supply problems.

markjwyatt · Oct 26, 2021

The pixels act as wells and are getting smaller. Maybe they are approaching the electronic Knudsen number (based on electron diameters) and photons are clogging some of the wells? Try some e+ (positron) spray and see if you can clear the wells. Be sure to use lead shielding. /chem-phys-sarcasm

shutterfinger · Oct 26, 2021

I'm an old electronics technician. I have intimidated a few engineers while doing repairs. IC (integrated circuits) have improved over the years and are much more stable in this age than they were in the 1970's. Yes they can still fail but its 99.999% likely they won't!
Now your camera's battery contacts and switch contacts can and will tarnish reducing the current flow in the camera. A low voltage or border line current flow to the sensor may cause it to not function properly giving the appearance of fading.
Contamination on the sensor, software changes, tarnished electrical contacts make the sensor fading a wild goose chase.

jvo · Oct 26, 2021

markjwyatt said:
The pixels act as wells and are getting smaller. Maybe they are approaching the electronic Knudsen number (based on electron diameters) and photons are clogging some of the wells? Try some e+ (positron) spray and see if you can clear the wells. Be sure to use lead shielding. /chem-phys-sarcasm

truer words have never been spoken.

gone · Oct 26, 2021

Pieter12 said:
with a lens mounted, it would seem pretty hard for vaping or other substances to deposit on the sensor

A lot of zoom lenses will suck in ambient air when they're zoomed, that's probably how a lot of it happens. I don't have a zoom lens (or a digital camera), but on my SLR's, w/ a prime lens the mirror stays pristine. However, the rear element of the lens manages to get dust on the side facing the mirror. Stuff gets on my focus screens, maybe tiny bits of mirror foam.

While cleaning my place, it was amazing how much film was on things. The previous resident was a smoker and had left an art poster/print on the wall that was covered in clear plastic. I never liked it, the colors were brownish and dull. But after a good wipe down it's a totally different piece! Looks great now.

Petrochemist · Oct 27, 2021

My 10+ year old digital cameras still have similar sensitivity to when new.
If there's a real drop off I suspect a very dirty sensor is the likely cause, with some cameras things can get remarkably grubby before it's noticeable in the photos - especially if you like shooting wide open.
Dyes in the filter stack may degrade in time, but digital cameras have not been around long enough for this to be significant. The very first digital camera was made in 1975 & I doubt 50 years of constant usage would be enough to cause issues with mass produced cameras!
FWIW fading of the dyes would make the camera more light sensitive (but less color sensitive), but oxidation/polymerisation could darken parts in time. UV would be the most likely trigger of either reaction & most sensors are only exposed to light of any form for much less than 1% of their existance.

couldabin · Oct 27, 2021

Thanks for all the great input. I found a lab that does sensor cleaning and will start with that. (I have to admit I hadn't thought of trying positron spray ...)

Paul Howell · Oct 27, 2021

The Sony is mirrorless, somewhat more of a possibility without the mirror that dust, smoke or other vapors will coat the sensor. I have a few cameras from the 90s, early Kodak and Sony point and shoots, the back screens are going out but when last tested the sensors were working just fine. The shutter failed on my 2003 Sigma SD 9, other body is still working no change in image quality. Remind me that I need to take it out for walk.

Oren Grad · Oct 27, 2021

Nodda Duma said:
Even if so, the symptoms wouldn’t be fading of the colors in the final image. It would result in color shifts towards magenta due to the demosaicing algorithm doing its job with what would then be incorrect scaling coefficients.

That's where it gets interesting - to think through what an actual mechanism of "fading" could be given the physical makeup of the CFA, and what that would imply for symptoms, taking into account the entire image-processing chain. Lots to learn here, just one question for now: why would damage to a CFA necessarily result in a magenta shift in particular?

Nodda Duma · Oct 27, 2021

If all three fade equally, both blue and red will let more light in, the combination after demosaic processing shifting towards magenta

reddesert · Nov 2, 2021

You should check if the lens is clean or has gotten some haze or fog on it before suspecting the sensor.

couldabin · Nov 3, 2021

reddesert said:
You should check if the lens is clean or has gotten some haze or fog on it before suspecting the sensor.

True.

grat · Nov 8, 2021

I can't think of any failure mode or degradation that would lead to less saturated images. I know there's usually a warning to not leave the sensor exposed to direct sunlight, but I would assume that would cause actual damage, and would show up as such.

My EOS 30D that I purchased 13+ years ago is still producing very nice images on those rare occasions when I pull it out.

Do image sensors lose sensitivity?

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