This Burning Out Of Sensors Through Pointing A Camera At The Sun

I've just spent some time looking on the internet for a definitive answer. After all, if it's not on the internet it isn't true, is it? (I had already failed to find a discussion in the various technical books I have). It appears that it is common knowledge that damage will occur, although no-one has actually seen an example of it. One person suggested that this was because digital cameras were normally discarded/replaced before they had been used enough. It's hard to refute a theory that can't be falsified, and so far as I've seen this may be such a theory. Another pointed out that this information (like much else on sensors) isn't made available by the makers, and suggested that it was a deliberate policy of keeping users in the dark (much as sensors apparently should be).

The only probable explanation I have come across is that prolonged exposure to sunlight causes dyes to fade, and this would affect the filters in the sensor. This certainly sounds reasonable, but I should add that I have coloured filters that are decades old and have not been visibly affected by exposure to sunlight. The accelerated aging of focused light might cause a small local discolouration, but I have never seen any effect from unfocused light. In this paragraph I have adopted an assumption that in general I disapprove of - that if you can't suggest a mechanism, then the effect doesn't exist. But when it seems difficult to actually find a verified instance of the effect, mechanisms are all I have left to play with.
 
I've seen with my own eyes last week a guy who pointed his eos 5d with 70-200 f4L attached and for 4 - 5 mins took 25 - 40 picture at 200mm of the solar eclipse last week. There was no damage at all to his camera and none to his eyes He got some good pictures though.
There is a well known video on YouTube of a DSLR sustaining sensor damage, but that was caused by a laser light show at a music concert.
 
redsnappa said:
During the eclipse last Friday I saw a guy with a eos 5D/70-200mm f4 combo photograph the eclipse with no protective filters on his camera or no protective eyewear. There was no damage to his eyes or to his 5D.
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I saw dozens of people photographing the eclipse with DSLRs. At a rough guess I'd say about 1/4 of them had no filter. Some of those were relying on passing clouds to provide enough dimming. Others simply regarded all the talk of burning out sensors as groundless hysteria. I had two cameras, one with 10 stops of ordinary ND filtration, one with 14 stops. I also took some photographs of the eclipse with no filters when the sun was enough obscured by cloud. No cameras were harmed in the making of my photographs :)
 
StephenM said:
I read a post within the last few months from someone who presented prima facie evidence of a "hot spot" of increased sensitivity that was apparently created by photographing the sun. It might have been on this forum. That's the only case I can recall of sun damage to a sensor, assuming that the hot spot was caused in this way. I can't recall what the final verdict was.
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It was probably this thread. Though the actual cause never seems to have been completely resolved (though the camera was repaired), it looks as though it was shutter damage rather than sensor.
 
Yes, that's the one:ty: . The only example I can ever recall seeing of sun damage to a sensor. And it wasn't even clear that it was sun damage.
 
Steve Smith said:
My point precisely. I can use a wide and a long lens to focus the sun at the film plane. The wide angle lens will focus the sun to a much smaller area than the long lens will.

My expectation is that it will be possible to burn a hole in some paper with the wide angle lens but not the long lens because the long lens does not focus to a point of light.
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The problem is that "the sun" starts out as a small point of light with a wide angle lens...it contains less energy (proportional to the scene). I doubt it will be enough to burn even tissue paper, but maybe.

At any given moment the light/energy emitted from the sun is fixed. The only way to change it is to change the distance to it, and we can't do that. If you zoom in tightly so that you are only seeing a portion of the sun, you are actually getting "less" total energy but "the same" energy per area (of the sun) ... the effect is similar to masking/metering a softbox.
The only way to start a fire by "focusing" (concentrating) the light energy is to take a lens' entire FOV (the sun as "a point" plus all of the scattered/spread light) and focus all of that to a single point. A magnifying glass will do that, but a camera lens will not. A camera lens will only project an "image circle," either in focus or not. And if you are projecting an image circle you are not changing the light energy distribution(concentration) in any way.

Edit to add:
A potentially significant factor is that using a bare lens will allow more high energy UV spectrum thru to the paper... A large range of UV is absorbed just by passing thru the glass, but more will still reach the paper than would reach a digital sensor (w/ IR/UV filter layer). The same is true for a lens used with a film camera or the human eye.
 
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steveo_mcg said:
Regardless how you meter you'll either blow out the sun or block out the rest of the image, I'm not sure what your point is.

Total energy remains the same, area of effect is the issue, silicone and the components can deal with with X heat per sq mm after that things burn out.
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I thought I was agreeing with your response...:)

The size of the sun in the image changes the exposure due to the "average gray" metering and not due to the total energy collected. It's like cropping an image... if you crop into just the sun the histogram will shift but the exposure (energy per area) does not.
 
redsnappa said:
During the eclipse last Friday I saw a guy with a eos 5D/70-200mm f4 combo photograph the eclipse with no protective filters on his camera or no protective eyewear. There was no damage to his eyes or to his 5D.
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I'm quite sure that during an eclipse, with the sun being blocked by the moon, that there is a whole lot less light energy getting to the sensor than in my example image with a bright midday sun in it.
 
sk66 said:
I thought I was agreeing with your response...:)

The size of the sun in the image changes the exposure due to the "average gray" metering and not due to the total energy collected. It's like cropping an image... if you crop into just the sun the histogram will shift but the exposure (energy per area) does not.
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Pre coffee replies should be filtered out! :)
 
Steve Smith said:
Please explain how the light knows the difference between a camera lens and a magnifying glass.


Steve.
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The light doesn't... it's the "optical design" of the lens system that makes the difference. And a camera lens will not focus it's entire FOV into a single point... it's not designed to do that. It's designed to project an image circle.

With a magnifying glass you change it's distance to change the "focus" and get a concentrated point. But with a camera lens if you change the (flange) distance you loose focus and have to refocus the internal elements... the net result is no change to elements w/in the image circle, there is no "concentration" of energy/light. A camera lens is designed to focus it's image circle only at flange distance and the tolerance is very small.
 
sk66 said:
But with a camera lens if you change the (flange) distance you loose focus and have to refocus the internal elements
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Look closely at a camera lens. When you focus, the whole assembly moves in and out on a helical thread. Move it further away to focus on close objects and closer to focus on distant objects (that's also how cameras with bellows work). The separate elements maintain their relative positions (prime lens).

Think also about extension tubes and bellows for macro. They move the whole of the lens away from the sensor to allow focus on a closer object.

A 50mm or 20 Dioptre lens is exactly that. It doesn't matter if it is fitted with a camera mount or a handle, it will do the same thing.

If you have a magnifying glass at home, use it to focus an image of your ceiling light or a table lamp onto a wall. Now try the same thing with a 50 to 100mm camera lens. They will both do the same thing.


Steve.
 
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The difference is that when you use a magnifying glass it "magnifies" the size of the sun and concentrates it into a smaller point. It's not "in focus," it's "concentrated;" you don't see "an image." A camera lens doesn't do that. It is akin to using a telephoto lens to project the sun as a point the size a wide angle lens would, but you can't do that with camera lenses...at least not at flange distance.

I will be interested to see what you find. I think that if you do manage to get tissue to burn it will be equally efficient with either lens... the only difference I can see will be the area of tissue ignited/covered by the sun when it is in focus. If the sun ever comes out I may try it myself just to see.
 
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So you can magnify something smaller?!!!

Get a magnifying glass and try to focus something onto a wall or a piece of paper. You will see that it works in exactly the same way as a camera lens.

Steve.
 
Like I said, you are focusing light energy and not "an image." If you/we do manage to get it to work the significant factors will be the lens diameter (entrance pupil size) and aperture (wider is better), not focal length. I.e. I believe the f-stop of a magnifying glass is f/1 and a larger lens element is more effective. And if it does work, I don't believe the lens will be at flange distance (i.e. camera mounted distance).
 
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Sorry, but a magnifying glass is just a single element lens. A lens is a lens, and the only difference between a magnifying glass and a camera lens is that a camera lens is more highly corrected. That does make for some differences in their properties, but both will act in exactly the same way with regard to the sun. A magnifying glass would normally have a short focal length, and hence produce a smaller image of the sun, but that's it.

You can use a magnfying glass as a simple close up lens, and you can use a camera lens mounted in front of another one as a close up lens. Both behave the same way, and for the same reason.
 
Hold a lens up to the wall pointed at your light, at the correct focus distance you'll see an image of the light bulb just as you would with a magnifying glass. You can use a magnafying glass as rudimentary lens on bellow focused cameras. The concept of a modern lens is exactly the same it is just more complex.
 
Well, it will be f/1 if the focal length of the magnifying lens is 50mm and the width is 50mm ---- ooh! Actually, it will be f/1 too if it's F/L is 750mm and it's width (diameter) is 750mm ~ that's the beauty of ratios! (all things being equal they remain equal)

As for images and point light sources well, a camera lens is the same as a 'Magninying' lens just that the camera lens is a compound of multiple elements. In fact, in this instance, it should be called a Magnifying Element as opposed to a lens. If you were to try and burn a sheet of paper with the focussed sun's rays (IR, UV and Visible) and simultaneously a cloud was alongside the sun's image you would see both the sun and the cloud. The main point being everything gets focussed/projected.... light aint fussy, it just obeys the Laws of Physics.
 
I missed post 96.

I just happen to have a magnifying glass on my desk, and I just measured its focal length as about 7". The diameter is 2.5". It isn't f/1...

That was an easy lens - it was circular. I also have a rectangular magnifying glass.
 
StephenM said:
I missed post 96.

I just happen to have a magnifying glass on my desk, and I just measured its focal length as about 7". The diameter is 2.5". It isn't f/1...

That was an easy lens - it was circular. I also have a rectangular magnifying glass.
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I checked one of mine... focusing on clouds (close to infinity) it's not f/1 either.
 
Here's someone burning a leaf with a camera lens... so it is doable. It doesn't look like a focused image circle or flange distance to me. That's probably due to what light spectrum is being focused in order to cause the burning (i.e UV).
The only other question is will a wider angle lens burn faster or just smaller... I have lenses of different FL's with the same aperture range and lens diameter. I'll test 400mm vs 70mm at f/5.6, and 200mm vs 24mm at f/2.8 (the 24mm has a slightly smaller front element).
 
The reason I think that it's much more likely with a wide angle lens is that pinholes burned into cloth shutter curtains are well documented. If longer lenses could do the same damage, there would be reports of large holes in shutters - but it's only ever pinholes.

All we need to prove the point is a bit of tissue paper, a couple of lenses and the sun. Not sure when the sun will be willing to take part!


Steve.
 
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Steve Smith said:
The reason I think that it's much more likely with a wide angle lens is that pinholes burned into cloth shutter curtains are well documented. If longer lenses could do the same damage, there would be reports of large holes in shutters - but it's only ever pinholes.

All we need to prove the point is a bit of tissue paper, a couple of lenses and the sun. Not sure when the sun will be willing to take part!


Steve.
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I think the reason it can/could burn is due to a lack of UV filtration (as in the days of film/cloth shutters)... you can't burn something by focusing a "full spectrum visible light bulb" or other "visible light" source (that I am aware of anyways). I believe the reason it is only ever "pinholes" that are burnt is because it is the focus of high energy (UV) light to a point that causes the damage and not the visible light we can identify/see. Meaning both a long FL and a wide FL will burn "pinholes" if focused to do so.
In order to focus IR light you need to "short focus" visible light. And IR is at the opposite end of the spectrum which means you (should) need to "long focus" visible light for UV... the focus offset required is greater for shorter FL's w/ IR, but I'm not certain about UV in relation to FL. I *think* that puts UV focus of the sun beyond "infinity focus" for visible light... at least with the lens distance fixed (i.e. mounted). The question here is, is there more visible light defocus required to focus UV with one FL vs the other... if so, the lens with less visible light defocus required has greater damage potential when mounted.
But, there are lenses that are CA corrected to include near UV/IR... AFAIK they are rare/specialized, but a "better corrected lens" will have a potential advantage.

And we're still left with the UV reactance/sensitivity of silicon (or lack of), and the IR/UV filtration that exists, when it comes to damaging a digital sensor (silicon is photoreactive to near UV and at least that portion is filtered out to prevent RGB color issues).
 
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I think I bow out at this point, as the discussion isn't going anywhere. I do however believe that there are a number of errors in post 105 above, but I lack the will at this point to go through in detail.

Steve - I suspect that this "focus to a point" issue is down to the image of the sun produced by a short focal length lens being smaller than that produced by a long focal length one and hence tending more to a point image of the sun. Your earlier point - that it's the energy per unit area that matters - still seems to be the actual factor involved.
 
StephenM said:
Steve - I suspect that this "focus to a point" issue is down to the image of the sun produced by a short focal length lens being smaller than that produced by a long focal length one and hence tending more to a point image of the sun. Your earlier point - that it's the energy per unit area that matters - still seems to be the actual factor involved.
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Yes. That's the main (possibly only) point I am trying to make. A strong and hence wide angle lens will concentrate all the light into a small spot which can cause heat. A weaker, long lens will not.


Steve.
 
I was curious about this question of what kind of lens made the best burning glass more than sixty years ago. So I carried out the appropriate experiments.

I'm reminded of what happened when the young naturalist Faber visited the august authorities of the French Royal Academy. They were debating at great length the philosophical question of how many legs a spider had. Faber lost patience with the arguments and ran out of the room to find a real spider. It took him a while. When he returned they had finished the debate and come to a conclusion based on the best arguments of the best authorities. Spiders had six legs. Nobody was interested in Faber's attempts to challenge authoritative philosophical opinion with something as trivial as an actual spider.

Of course we'll have to wait for a hot sun. In the meantime some might like to note that you can burn a hole in paper or even sheet metal with a powerful enough laser of any wavelength of light, including IR & UV. Note too that a good clue to the differences in focus distance, size of focused spot, etc., between IR or UV and visible light is given by the chromatic aberration of a single element lens, such as a magnifying glass or pair of reading glasses.
 
Simple experiment, no camera involved, just a wide-angle and a telephoto, focusing the image of bright sun on a piece of black paper. With the longer lens, 200mm f/4, the paper begins to smoulder after a couple of seconds. With the wide-angle 17mm f/4, I couldn't get it to burn at all.

Pretty obvious then that longer lenses are much more of a problem, but in practise much less likely to be an issue just by leaving the camera sitting in the sun. The longer focal length ensures that the sun is much less likely to be in the right position (field of view) and less likely for the image to be in focus, too.
 
Steve Smith said:
How can a long lens focus UV to a point?

(I'm not arguing that it can't but would like to know how it can).


Steve.
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A source that starts as a point of light and is "in focus" on the sensor is again a point of light. But maybe I shouldn't have said "pinholes" but rather a longer lens will burn a larger "pinhole."
I still don't see an advantage of a wide angle over a longer lens... there is no "concentration" advantage. With a wide angle lens it starts small and ends small.
You can correlate it to photographing a light source from different distances. As you move further away it becomes smaller, but not "dimmer" (i.e. it will spot meter the same). And as you move closer it becomes larger, but not brighter (per area)... This differs from the inverse square law because you are photographing the light source directly, but it has the same principle/cause.

When we see drawings of a lens focusing it shows parallel rays being combined to a point of focus. But this is not "concentration" of light as such. It is simply the collecting of the scattered rays emitted from a single point being brought back to a point. Meaning FL doesn't matter much as far as I can see. This same scattering/focusing is happening to every single point from the source and on the sensor regardless of the FL.

What does make a difference is the diameter of the objective lens... as it will collect more of the scattered light from an emission point and bring it back together in focus.
I've tried to diagram the effects as I understand them.
A longer FL lens "get's closer" and collects "more" but projects it to a larger area. And shorter FL collects less but projects it to a smaller area; there is no net gain.
But if you only increase the diameter of the element it collects "more" and projects it to the same size... thus a net increase in energy focused. The other factor is the aperture's physical diameter of the lens, and wider is better because it causes less diffraction.

View attachment 33605
 
HoppyUK said:
Simple experiment, no camera involved, just a wide-angle and a telephoto, focusing the image of bright sun on a piece of black paper. With the longer lens, 200mm f/4, the paper begins to smoulder after a couple of seconds. With the wide-angle 17mm f/4, I couldn't get it to burn at all.

Pretty obvious then that longer lenses are much more of a problem, but in practise much less likely to be an issue just by leaving the camera sitting in the sun. The longer focal length ensures that the sun is much less likely to be in the right position (field of view) and less likely for the image to be in focus, too.
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I think the primary difference here is the physical aperture sizes... assuming roughly equivalent lens diameters.

The best lens *should be* a longer FL with a wider diameter objective element and a larger physical aperture diameter...and it should burn a larger hole.
 
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Ive been thinking about this some more, and I have an argument as to why there will be no difference between a wide lens and a long lens of equivalent aperture (f ratio, not absolute).
Lets take a 14mm f2.8 and a 200mm f2.8, both at f2.8, both pointing at the sun. If both lenses take a shot of 1/8,000s, they will both be equally exposed, so that means an equivalent number of photons land on each of the photosensors the sun is focused on (there will be more energy overall with the longer lens, but I think what is imporatant is the energy per area). I think this means that the energy / heat will also be equal.
 
Rapscallion said:
Ive been thinking about this some more, and I have an argument as to why there will be no difference between a wide lens and a long lens of equivalent aperture (f ratio, not absolute).
Lets take a 14mm f2.8 and a 200mm f2.8, both at f2.8, both pointing at the sun. If both lenses take a shot of 1/8,000s, they will both be equally exposed, so that means an equivalent number of photons land on each of the photosensors the sun is focused on (there will be more energy overall with the longer lens, but I think what is imporatant is the energy per area). I think this means that the energy / heat will also be equal.
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Yes...
Equivalent f/stops means that equivalent light reaches the sensor... and the exposure of the sun (light/energy/heat per area) will remain constant between the two lenses.
 
Note that whatever you've set the aperture to, that only affects the moment of exposure. Otherwise, when focusing, composing, using live view, you're in effect making much longer exposures at the maximum aperture of the lens. Unless you're using a lens with a manual aperture control ring.
 
"F-stop" is problematic in this discussion because the rated f-stop does not necessarily equate to the actual/physical aperture diameter. The rated f-stop is based on the "effective/apparent" aperture diameter as seen by the objective element.
I.e. a constant aperture zoom lens has internal elements that change the magnification/effective size of the aperture as seen by the objective lens, but it's physical size doesn't change.

I'm kind of at a loss as to how one would do the test w/ various camera lenses to definitively identify the relevant factor(s).
*A longer FL lens at the same f/stop has a larger effective aperture diameter which means equal light transmission, and that *may* mean a larger physical aperture diameter... but you don't typically have access to measure the diameter directly.
*A longer FL lens has a larger diameter objective element for equivalent max aperture... but this is necessary in order to compensate for light (energy) loss over the longer FL distance (i.e. to keep the T-stop close to the F-stop). And it also affects the effective aperture... i.e. if a lens of the same FL has a smaller objective element, and the aperture diaphragm opens to the same physical max diameter, it will have a lower f-stop rating. The objective lens diameter may not be the same as the front glass (if equipped with protective glass), and it is certainly not the filter size... you would have to measure it directly and that might be difficult.

With a compound camera lens the FL, f-stop, and lens diameter are interrelated, and they balance each other out in terms of light transmission.
IMO, it will come down to a lens with/at a wider f-stop.
For the same f-stop it will/should be the longer FL lens... but the reason the longer FL lens would win isn't as obvious as one might think. I believe the longer FL lens will win because it is heating up a *larger area*. And that inhibits surrounding areas from absorbing the heat at the very center... it should still start as a "pinhole" and move from the center outward.

Still no sun...
 
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Sun today! Clear blue skies.
I tested 7 lenses @ 8 FL's. Sun ~15* below vertical. I held the apertures open to maximum where they did not have manual rings. I measured the objective lens diameters to the best approximation. I used a 30sec limit as it's quite long for any exposure of the sun, and it was difficult keeping the paper steady that long w/ the occasional breeze. Standard weight inkjet printing paper and I focused the visible light to the smallest achievable size w/ focus set to infinity.

Sigma 12-24/4.5 @ 12mm, 56mm objective- no ignition in 30 sec.
Nikon 16-35/4 @ 16mm, 48mm objective- no ignition in 30 sec.
Nikon 24-70/2.8 @24mm, 61mm objective- no ignition in 30 sec.
Nikon 24-70/2.8 @70mm, 61mm objective- no ignition in 30 sec.
Nikon 70-200/2.8 @200mm, 70mm objective- no ignition in 30 sec.
Nikon 80-400/5.6 @ 400mm, 70mm objective- no ignition in 30 sec.
Nikon 50/2, 28mm objective- ignition at ~20 sec.
Zeiss 85/1.4, 60mm objective- ignition at 3-5 sec.


Conclusions:
FL alone makes no significant difference... same results in the 24-200mm range at f/2.8.
Larger diameter front element to achieve equivalent effective aperture makes no significant difference... 200/2.8 w/ 70mm objective had the same result as 24/2.8 w/ 61mm objective.
A longer or shorter FL w/ a smaller aperture is definitely not a benefit.

The only successes came with more simple prime lens designs and larger apertures. I believe a significant factor here is the fewer elements w/in the lens which absorb/decay "less" UV/near UV. I also think that because the lenses are more simple primes the f-stops are more closely associated with the true aperture diameter as opposed to the effective diameter... but I don't really know if that's of significance.

As expected, the best result came from a lens with a relatively large objective lens and correspondingly larger aperture. What I didn't expect was how little success I had in just igniting paper.
 
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Quick follow on test:
Zeiss 85/1.4 w/ ND8 @ f/1.4, bare at f/8 and f/16 (i.e. more feasible settings)... no ignition w/in 30sec.
Focused half way between 50ft and infinity (the last two markings) @ f/1.4... no ignition w/in 30 sec.

Conclusion:
Don't take shallow DOF images focused on the sun using a wide aperture prime lens...
 
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