Help please, CCD question.

[Ferdinand]

Well, sometimes, ignorance is bliss...... but then I discovered how to check for dust bunnies on my CCD and this is what I got....

http://mcauslan.force137.com/misc/ccd.jpg

Those bumps are just the wall. *phew*

But those specks, are they big enough or many enough to be of concern?

Regards,
Ferdinand

[garethhhhh]

...are they big enough or many enough to be of concern?


Whoa! those are the darkest dust bunnies I've ever seen! :shock:
You should clean your senson before you take another shot.
Have a look at this (http://www.pbase.com/copperhill/ccd_cleaning) tutorial on censor cleaning. 8)

btw :arrow: what are those circular lines all about? :?

[Cadwell]

They are big enough to be of concern if you see them in your photographs. If you've never noticed them until you specifically went looking for them then I guess the answer is "no". Of course now you know they're there... :roll:

It's all too easy to get into the "Lady Macbeth Syndrome" where your lenses / sensor are never clean enough and you wander round muttering "Out, damned spot!" all the time... :lol:

[garethhhhh]

It's all too easy to get into the "Lady Macbeth Syndrome" where your lenses / sensor are never clean enough and you wander round muttering "Out, damned spot!" all the time... :lol:

LOL! :lol:

True, but it doesn't hurt to clean it once every month or two to avoid nasty surprises.

[Jesper]

Have a look at this topic, I just cleaned my 10D sensor for the first time (before & after images in the thread):

http://photography-on-the.net/forum/showthread.php?t=27848

By the way, strange rings in your photo..... is that a lens artifact?

[Ferdinand]

Thanks everyone :) Looks like the CopperHill CCD Cleaning page is the Bible of cleaning CCD/CMOS. There was even a positive comment given by Chuck Westfall of Canon USA.

The only question I have is that normally you blow on lens surfaces before giving it a wipe to avoid those particles from scratching it but in CCD/CMOS case, blowing is a no no? Just go at it with the swab?

Jesper, the ring is probably caused by my 50mm f/1.8 Mk.II ? I am not sure any expert here care to comment, it looks suspiciously like the concentric ring found on your focusing screen, but if so how did it get on the CMOS? hehehehe...

By the way, BH I found them to carry the Eclipse cleaning solution but they cannot ship it :( Does anyone know of a store here in the San Jose, Bay Area what carrys it?

Regards,
Ferdinand

[AJSJones]

When I was cleaning my sensor, I had more dust bunnies than the original in this thread that had accumulated because I rarely use small apertures (I use the light to shorten exposure mostly). I didn't get rid of every last one but they will show up in small aperture shots with , say, sky in them, but are clonable for the most part.

There was a thread long ago commenting on the rings but I couldn't find it. However, when I was looking at my exposed filter/sensor during cleaning, I could see them when the light was at the appropriate angle and they were definitely ON the sensor/filter. My guess is that it's a fresnel to guide the light rays from hitting the sensor obliquely, where they might not "reach" the photosensitive elements, to hitting them more close to vertically. There was a lot of discussion about this problem when digital cameras came out - "film doesn't care about the angle of incidence while digital sensors need the light to come from above, so there will be artifacts at the edges of the image.." Using a fresnel close to the sensor (i.e. part of the IR/AA filter) makes sense and would explain these rings.....

Anyone know of information on filter/sensor assemblies from academic or manufacturer sources? - I can no longer find the diagram of a cross-section of a typical filter/sensor assembly I saw once although I do recall some parts of them being made from lithium niobate, but I don't recall any fresnel in the description

Andy

[KennyG]

By the way, strange rings in your photo..... is that a lens artifact?

You often get those if you use a UV filter on the lens. The are known as Netwton rings. Another reason why I never use filters.

[Ferdinand]

I was shooting at a baseball game last week, and player were kicking up dust everywhere, won't having a filter on your $1700 lens be better than nothing? They are not truly visible on an actual photos are they? I guess I am just a new L-coholic who babies his lens too much :-/

Unless of course you have insurance on your lenses? If so who is your provider and how much do that charge on lets say a 70-200mm f/2.8L IS lens? I am interested in getting it for my lens.

Regards,
Ferdinand

[AJSJones]

You often get those if you use a UV filter on the lens. The are known as Netwton rings. Another reason why I never use filters.

KennyG - A UV filter (or any filter for that matter) can sometimes cause unwanted internal reflections that can aggravate flare problems or decrease image contrast, so being judicious with filter use is a wise approach, to be sure. The sensor assembly is more reflective than film so internal reflections are a bit more problematic with digital imagers than film.

However these are not related to Newton's rings. Those occur only when two pieces of glass are sufficiently flat that they can get close enough to each other to be within a few wavelengths of the light passing through them - i.e. within about a few thousandths of an inch. You get the same effect from a very thin layer of oil on top of water.

The rings in the picture above come from the fresnel grooves engraved (and perfectly centered on the optical axis) somewhere in one of the layers of the anti-aliasing filter/IR filter assembly that sits just above the sensor.

Andy

[Jesper]

The rings in the picture above come from the fresnel grooves engraved (and perfectly centered on the optical axis) somewhere in one of the layers of the anti-aliasing filter/IR filter assembly that sits just above the sensor.

Does that mean there is something wrong with Ferdinand's camera? Or might it be in his lens? I haven't seen something like that in my photos, also not in my own heavily contrast stretched dust bunny test photos (which I made with my 17-40L without filter).

[AJSJones]

I see it sometimes but not others, and I've seen others also post similar pictures. Not entirely clear what conditions are required to generate an image where the lines are visible.

I'm not worried. I downloaded the above image, cut out a portion that had little image (i.e. wall) info and did autolevels on it. You can enhance their appearance but it's not much greater in intensity than the other noise that's there - it's just that it has a recognizable pattern to it - only visible when you stretch a few levels out to fill the whole luminance range, not something you would do very often!

Again, if you do the sensor cleaning routine to the point where you can see the imager and rotate the camera around so the light hits it from different angles, you can see the rings on the sensor assembly surface. i.e. it's not a camera or lens bug, it's a FEATURE!

Don't worry, take pictures!

Andy

[Johnnynf]

Unless of course you have insurance on your lenses? If so who is your provider and how much do that charge on lets say a 70-200mm f/2.8L IS lens? I am interested in getting it for my lens.

I actually just got a "Personal Articles Policy" from State Farm (provided you live in the US) for my camera equipment. I don't know if insurance premiums can change depending on where you live, but the rate I got was $1.12 per $100 insured...this is of course a yearly rate. I got insured for $4000...and it is costing me $45 a year...or $3.75 a month. I don't know about you, but that is reasonable to me. It covers almost everything...it even covers if you simply drop the lens by accident. There are only a few certain things that aren't covered...one of them being nuclear war...I think another might be damage caused by vermon (although I may be wrong)...so if you are ever camping, don't let a bear get to your camera. :D It gives me piece of mind when I am using the camera.

[Ferdinand]

Thanks Johnny, I have State Farm for my car insurance I think I will call them now to insure my camera. That is awesome info.

Best regards,
Ferdinand

[KennyG]

Unless of course you have insurance on your lenses?

Actually, yes I do. All my equipment is fully insured (about $45,000 worth) even for accidental damage. I also have $4m of public liability insurance (I can't shoot without it). However, none of this would be any use to you as it is for the UK only.

I'm sorry but I don't treat my lenses or cameras like babies. To me they are working tools. They are well looked after, but the odd ding and battle scar, as long as it does not effect performance/quality, is something I live with. You can't spend 6 to 8 hours at a stretch for 25+ weekends a year trackside without showing some wear and tear. I hasten to add, in 25 years I have never had a damaged lens or even the slightest scratch on the glass and all I ever use for protection is a lens hood.

I don't want to get into the filter argument again. I know what works for me.