"Sensor Flares" - what's the truth?

[vcassel]

Epic post, Barry! Just really good.

[broughtonfilm]

What else do I have that has interchangeable lenses? Well, look, there's my Super16 film camera, let's try that. Obviously that won't have the issue, because it's not made by Panasonic... okay, let's shine the light in and ...

Well, what do you know. There it is. The exact same lens flare. The same "sensor flare" is happening on a 16mm film camera. (No video to show it, because the viewfinder opening on the camera is about 1/4" in diameter and I couldn't figure out how to film the ground glass through that opening). But I assure you it's there and looks very similar to the AF100/GH2.

It is not a regular lens flare but the flare in which the sensor's surface plays the critical role. The sensor reflects back some rays of light, acts like a mirror in a way. It is really not a big discovery, this phenomenon has been known for years. You mixed all kinds of flares all together here which only adds confusion (or uncertainty if you prefer).
There is a misunderstanding of what causes this particular phenomenon and the quote from your article above proves it.
You can't assume that Super 16mm film camera (or any other film camera) exhibits the same issue (as stated in your article) simply by looking through its viewfinder. What you see through its viewfinder does not include involvement of the surface of the emulsion ( which in case of a film camera is an equivalent of the sensor) instead it shows set of issues introduced by the viewfinder's optics itself combined with any possible lens issues. Even if the emulsion's surface was actually reflective enough to cause the problem, construction of the film cameras simply does not allow you to see what happens while the film is being exposed - whether it is a non-reflex or a reflex camera. It is completely different in most video cameras - you actually witness that moment "live". In a non-reflex camera we look through an independent optical viewfinder system which is not connected with actual lens-to-emulsion light path, it is obvious. In a reflex camera what we see through the viewfinder is not what is being exposed but its counter phase - the shutter is in a viewing position and closes the lens-to-emulsion light path: no light hits the emulsion at the moment of viewing (given that you keep your eye on the viewfinder and not allow any rays of light enter it "back door"). Furthermore, in reality what you see in the viewfinder of a reflex camera is not 100% the same as the image that is actually being captured by the camera- certain things seen in it are simply introduced by the viewfinder's optical system (i.e viewfinder's chromatic aberration, some additional flare, and obviously any frame markings). Yes, certain film movie cameras have issues with internal reflections (i.e ARRI 2C has a flicker problem, reflection coming from the ground glass, etc.), however, usually you can't evaluate them simply by looking into the viewfinder (often you would see some issues that are not being captured and vice versa). Once again, mixing this all together in your article means that you are talking about flare issues in general, not this particular type. It simply needs little bit more attention.

[Barry_Green]

Clearly the film flare is an extreme example, although I do think it would be comical if such a flare actually did show up on film. I can't think of any examples, but I wouldn't be surprised, because film isn't a perfectly matte surface and if you're overloading such an incredibly bright light directly onto it, it may very well reflect back. I'll try to dig out some ground glass to see if anything shows up when removing the viewfinder and mirror from the equation. And, I'm testing a new S16 camera soon, so I'll run the LED hyper-bright flare test on it.

Regardless of whether it happens on film or not, the fact remains: all interchangeable-lens video and digital cinema cameras are going to be subject to this same type of flare. It isn't a design flaw, it's the way video cameras are made, and furthermore, it really isn't a big deal. The original blog tried to paint it as an AF100-specific issue, and that is patently false. Had the article been more along the lines of "interchangeable-lens video cameras may have more flaring than you're used to on a DSLR or fixed-lens video camera", that would have been fine; it was the incendiary, inflammatory nature of the article, designed to scare people, that caused me to delve into the level of research I did for this article. Reflected flares are nothing new. They are not the exact same as typical lens flares, no -- but the remedy for both is the same. People have had to deal with flares of all types for a long time. There is nothing new here, there is no camera fault, there is no design flaw, it will happen on any interchangeable-lens video camera if a bright-enough light is shined directly into the lens, period.

From what I understand, Fujinon and Angenieux have actually developed new coatings on the rear elements of their newest digital cinema zoom lenses to reduce this effect, specifically because it can and does happen on digi-cine cameras like the Red, the Epic, the F3, and the AF100. If you really had a circumstance where you absolutely had to shine a massively-overexposed light directly into the lens, and simultaneously not see a reflected flare, you should probably be looking at renting a lens that's made to handle that task.

For the rest of us, a little exposure control and a little composition control are enough, or more than enough, to render the issue moot. I give you an example of someone who just shot the AF100 entirely at night, doing nothing but pointing the camera directly into lights. This was a largely uncontrolled test, and I dare say it was pretty much a worst-case scenario.


Look at how many shots there are, and count how many times the "sensor flare" shows up.
First shot, buildings, black with bright lights, no flare/ghost.
Second shot, extremely bright headlights, yep it's there.
Third shot, lots and lots of bright windows, and an extremely bright spotlight on the top of the building. There's a little bit of the ghost as he pans right, but they likely most audiences would never notice it, and if they did, they'd probably chalk it up to "flare" because, when you point a light that bright into a lens, you've always gotten flare -- whether it's typical or "ghost", doesn't really matter, in that shot it just looks like a flare.
Fourth shot, lots of headlights, no flare, no problem.
Fifth shot, big spotlight, lots of windows, no flare, no problem.
Sixth shot, lots of bright headlights pointed directly into the lens, no flaring, no ghosting, no problem.
Seventh shot, "Mother Annas" sign, a big bright white light right in the lens, no problem, no flare.
Eighth shot, the clock tower -- no flaring.
Ninth shot, closeup of the clock tower, lots of bright lights -- no ghosting, no flaring.
Tenth shot, major headlights, super-bright streetlights, shop lights, all pointed in the lens -- no big ghosting at all. There's a little bit of halation around some of the super-bright streetlights, and there's a few little tiny specks of purple reflected flare, but -- this has got to be one of the worst-case scenarios ever, and I dare say no rational person would even notice it.
Last shot - mega streetlights and headlights, everywhere. Looks just like I would expect it to. Lots of halation and flare, but nothing out of the ordinary.

I reiterate -- this whole issue has been massively overblown, there's absolutely nothing out of the ordinary here, and flare control is something that any competent shooter would need to be aware of and manage, and you absolutely can get bright lights in your shot without seeing some big scary ghost.

[broughtonfilm]

I'll try to dig out some ground glass to see if anything shows up directly on the film.

If I understand correctly you want to put a ground glass on the film plane (in the place of the film) and look through it with a magnifying glass, correct? I appreciate the effort but this won't prove anything either because then it will be the ground glass' surface reflecting the light and causing another problem (it has a different reflective property than film's emulsion). The only way to test it is to shoot the actual test on film (I think I kinda know the results - no issue , but who knows).

[Barry_Green]

And I will do so... it just takes a week to get film back, there's no labs nearby. I was saying that the ground glass test would eliminate the viewfinder from the equation. I suspect that with a bright enough light, it's possible that it will show a reflection. The film surface would have to be absolutely nonreflective in order for it to prevent any sort of flare, and just looking at film, it's clearly reflecting light, so it's possible. I'm not saying for sure that it will happen, but if it does happen, I'll find out.

[dcloud]

since when did this lens flare actually became an issue?
the guy's first post was that article and he made a blog post specifically for the lens flare. its obvioys he was spreading FUD and looking for attention

[Georgelum]

Thanks Barry, I just bought 2 AF 100s and have been looking for a nice assortment of lens' when I came across this thread. I have been using the Panasonic 2000, HVX 200, 200A for years. No real problem with lens flare/ghosting etc. I just shot my first test this morning of a sunrise on the lakefront with the AF 100/Canon EF 16-35 & Kipon mount. I will be looking at it on a Panasonic 17" monitor tomorrow with my DP. Now, back to my search for a nice lens package. P.S. I was really upset when I read the post that started this thread. Thanks for the thorough follow up. GE

[Noel Evans]

If I understand correctly you want to put a ground glass on the film plane (in the place of the film) and look through it with a magnifying glass, correct? I appreciate the effort but this won't prove anything either because then it will be the ground glass' surface reflecting the light and causing another problem (it has a different reflective property than film's emulsion). The only way to test it is to shoot the actual test on film (I think I kinda know the results - no issue , but who knows).

Regardless, take the film component out of it for a moment and weather it happens or not means little as it does happen on Red (I shot a heavily flared MV in Tokyo in January - flares were the point and its there) and F3 for example and a few quick tests show me I can get it easily on the 5DMKII. That being the case, and the fact we agree its there - whats the point you're trying to make?

[broughtonfilm]

Regardless, take the film component out of it for a moment and weather it happens or not means little as it does happen on Red (I shot a heavily flared MV in Tokyo in January - flares were the point and its there) and F3 for example and a few quick tests show me I can get it easily on the 5DMKII. That being the case, and the fact we agree its there - whats the point you're trying to make?

My point was that because Barry made reference to a film camera in his article it proved that he was mixing different types of flares all together and that he was talking about flare issues in general, not this particular type and that it needed more attention.

[David G. Smith]

Watch any movie from the '70s and you will see lens flares galore. Vilmos Zsigmond turned them into an art form, and won an Academy Award for Best Achievement in Cinematography for a movie where lens flares were added to special effects shots to increase their realism ("Close Encounters of the Third Kind").