Spots on CMOS sensor (EX3)

[Christopher Dye]

I purchased an EX3 and I am very pleased with it, but there's one little thing I'm wondering about. I looked everywhere here and other websites for others who may have encountered this anomaly to no avail.

The pictures the EX3 produces are great and I saw no problems until I aimed the camera in the direction of direct sunlight without the ND filter on. What I saw was pretty startling at first. There were little white spots all over the picture. It seemed like it might be dust, but it's a brand new camera.

Setting the ND Filter to ND2 basically got rid of it as did aiming it away from the sun, but I'm wondering if there's something wrong with the sensor because I can't for the life of me find anything on the internet about anyone else experiencing this 'artifact' or even mentioning it.

Looking at the manual closely on page 141, I noticed this paragraph about 'phenomena specific to CMOS sensors':

WHITE FLECKS

Although the CMOS image sensors are produced with high-precision technologies, fine white flecks may be generated on the screen in rare cases caused by cosmic rays, etc.

The white flecks especially tend to be seen in the following cases:

When operating at a high environmental temperature
When you have raised the master gain (sensitivity)
When operating in slow shutter mode

Again, the picture is great indoors and outside with the ND filter on (or aimed away from sunlight), so I'm believing it may be the CMOS 'cosmic ray' phenomena the manual refers to, but I am curious if any of you other EX1/EX3 owners have this same phenomena when you aim your camera towards sunlight without the ND filter on.

[Greg Boston]

What the manual is referring to there is 'stuck pixels'. These would be visible without aiming the camera at the sun.

-gb-

[Ray Bell]

I'm not sure if your situation is a dirty sensor but sooner or later every EX3 owner will
have to come to grips that the sensor will get dirty because you have the ability to remove
the lens and dust and dirt will find its way onto the sensor...

Here is one solution that the DSLR users are using to remedy the inevitable....

Copper Hill Images - CCD/CMOS Cleaning Tutorial - Introduction

[Greg Boston]

Originally Posted by Ray Bell

I'm not sure if your situation is a dirty sensor but sooner or later every EX3 owner will
have to come to grips that the sensor will get dirty because you have the ability to remove
the lens and dust and dirt will find its way onto the sensor...

Here is one solution that the DSLR users are using to remedy the enevitable....

Copper Hill Images - CCD/CMOS Cleaning Tutorial - Introduction

Works a bit differently with video cameras Ray. There are actually 3 sensors and they mount to a prism block which splits the primary colors. But before you ever get to the prism block, there is an OPLF (optical low pass filter) which brings the resolution down a bit from the glass.

regards,

-gb-

[Ray Bell]

Thanks Greg.... yes... what most folks don't realize is that they are not cleaning the sensor, they are actually cleaning the filter...

[Steve Phillipps]

Does sound like micro specs of dust to me - the bane of all digital sensors, I've had real problems with Phantom cameras getting dust on the sensors, and at £2000 a day to hire you don't wanna look at the shots and then spot it!
If it is dust then there are plenty of SLR dirt removal kits out there, and they work well, but there always seems to a little bit that gets missed. Olympus SLRs have a vibrating sensor that shakes off dust every time you power up, which sounds gimmicky but actually seems to work really well.
The spots would disappear with NDs on because of course that forces you to widen the aperture, and while the dots are still there they are out of focus so you can't see them (incidentally it's a good idea not to go below about f5.6 in any case).
Steve

[Serena Steuart]

Originally Posted by Christopher Dye

so I'm believing it may be the CMOS 'cosmic ray' phenomena the manual refers to.

A hit by a Cosmic ray is rare and transient, so this isn't your worry.

[Christopher Dye]

Thanks for the replies. I find it hard to believe that that much dust collected on the sensor already as I only took the lens off once.

I attached snapshots of video with said spots. First and second picture are without the ND filter on. The second picture is without the ND filter on and with the aperture closed down. The third picture is with the ND filter on and as you can see, looks okay.

[Alister Chapman]

If the dust is behind the lens changing the aperture won't make any difference to the size or shape of any flecks as it only affects the depth of field of the lens and thus only objects in front of the lens. However brighter subjects do tend to mask and dust as the light swamps the shadow caused by the dust.

However It is possible that the dust is in or on the lens. This would only show up as flecks or dots with very small apertures as you would have when pointing at bright objects with no ND. Such very small apertures allow objects in or on the lens to start to come in to focus. If this is not the case then the dust is possibly be behind the lens, either on the rear of the lens, the IR/low pass filter, the clear (ND) filter or the face of the optical block. As there is no focusing mechanism between the sensors and these items the focus on them will never change. Often dust and dirt behind the lens shows up as a donut shape. You should also know that there is a clear ND filter. When the ND is off a clear glass filter is selected to keep the amount of glass between the lens and sensor the same as when you have an ND selected.

Try pointing the camera at a bright subject (I would not recommend pointing it at the sun) and try to slowly move the ND switch to see if the dust moves as the filters move.

As has been pointed out, you can't clean the sensors, nor can you clean the optical block or the ND filters without dismantling the camera. The only thing you can clean is the IR filter which is the outer most part of the optical chain.

[Steve Phillipps]

Sorry Alister but that's not true. Try it with a DSLR or with a camcorder. If you shoot at f22 then dust and marks on the sensor will be clearly, sharply defined, while at f2.8 they'll be invisible. Same goes for focal length, the greater focal length, less depth of field so less sharp the spots.
Steve

[George Kroonder]

Christopher,

Try to find out if it is dust/spots in the lens. Shine a light (flashlight, desk light, w.e.) into the lens and look through the other end or 'project' onto a piece of paper. You may need to move the lens/light around a little.

In the outside elements of your lens are clean you may have to take/ship it to Sony to get looked at.

George/

[Alister Chapman]

OK, slight confusion I didn't word things clearly. I agree that changing the aperture will make the appearance of dust behind the lens change because the size of the light cone changes, i.e. becomes smaller or wider and thus softens or sharpens the offending spots. Just the same as a shadow from a point light source will be sharp while a large diffuse light source will produce a very soft shadow. With a wide iris the shadow of the dust becomes so soft and diffuse that it is basically invisible, but with a small aperture the shadow becomes more pronounced and thus the dust becomes visible. However this has nothing to do with depth of field. How on earth can depth of field affect an object behind the lens, an object that is never in focus anyway?

As Christopher is seeing white specs they are more likely to be ahead of the lens where they are illuminated. dust behind the lens tends to show up as dark spots as what you see is the dusts shadow. The frame grabs certainly look like dust or dirt on the lens.

[Wacharapong Chiowanich]

My guess is the dust/water vapor spots being on the clear ND filter (when ND Off is selected). You should first try Alister's method.

Wacharapong

[Christopher Dye]

Thanks again for the tips and suggestions, but I have a sinking feeling that I may have to have Sony take a look at it. There's a service center about ten miles from where I live here in Los Angeles.

The lens and even the sensor (at least that front green filter part) looks pretty clean. It is, after all, a brand new camera, so I don't think it's outside dust or anything.

I'll give an update after I take the camera in for an inspection.

[Christopher Dye]

Okay. I didn't make it to Sony because of car troubles, but I will eventually take the camera in.

I wanted to show a better picture of the 'particles' on the sensor (or glass filter). I should point out that they have a shimmering and sparkling quality on the video. As I move the camera, the dots change their hue, red, green, white, blue. Almost like christmas lights. They also have sharp black dots in the middle.

Again, this is only when it's pointed in the direction of sunlight. You do not see these under artificial lights, even bright ones.

I did examine the sensor more closely and there seems to be very fine tiny particles either on that glass filter in front (which I actually didn't realize was there before it's so clear) or possibly on the green filter before the sensor (which I did notice).

I cleaned the back of the lens with lens tissue, so I don't think the particles are on the lens.

Surprisingly there's nothing in the manual about cleaning that front glass protective filter in front of the sensor, but I was wondering if it's safe to clean it with lens tissue? I think it's only glass, but I'm a little leery about it.

Out of all the EX1/EX3's out there, I'm amazed I seem to be the only one with this problem.