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08/30/2012 11:08:19 PM · #51 |
Hey  DrAchoo, if you'd like to send this back my way, (if it's still around anyway), I think I'd like to do some destructive testing on it.
I would also request a small bag of local dirt as well, since our local soil is pretty much silica free here. |
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08/31/2012 04:20:55 AM · #52 |
Originally posted by Cory:
Funny enough, I've started to just blast the shat out of my sensor with canned air, holding the straw only mm's away from the sensor... works like a champ and it is super fast/easy... |
I was told not to use canned air on the sensor because of the propellant leaving a residue
I use a rocket blower, although the 5d mk11 claims to sensor clean on power off seems ok so far |
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08/31/2012 09:14:38 AM · #53 |
Thanks Cory, never really looked into scotch tape method.
i use gentle "sensor cleaning kit" stuff with atleast hplc grade cleaner (1ppm max evaporation residue. Sometimes the lc/ms stuff is similarly priced via my company, but never thought to take the extra step to change whats in the kit.
Message edited by author 2012-08-31 09:15:52. |
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08/31/2012 10:01:15 AM · #54 |
After quite some discussions with chemist colleagues on this topic, I made extensive experiences myself.
My conclusion: Scotch Magic tape from 3M gives by far the best results. The adhesion is not too strong with this brand and you can smoothly remove it again. It is not easy to put it on the sensor without air bubbles, but this is not a problem, just repeat the procedure. It does occasionally leave a residue of adhesive on the low-pass filter (visible with the naked eye), but it can easily be removed again with an additional Scotch tape.
The only valid objection I heard about Scotch tape is that you could eventually peel off the top layer on your low-pass filter. In most cameras I believe this is a very thin anti-static layer made of ITO (same as on iPads & co). It is not something which you could see with optical instruments, which also means that the image quality of your camera will never be affected. Personally I do not find this a concern at all.
My opinion about Eclipse: totally over-priced and needlessly toxic. If I have to use a liquid cleaner inside my camera, I use isopropyl or ethyl alcohol. What I do not like with liquids is that when you have greasy residues on the low-pass filter, you spread them over the whole surface and you have to repeat the process several times. The evaporation residues come usually from the dirt, not the alcohol, therefore I found standard grades mostly OK to use.
Compressed air: cheap brands have oily residues from the air compressor. Expensive brands are, well, expensive.
Â
Anyway, I recommend to everybody to make his own trials on a small glass plate (like a microscopy slide), before you attack the real thing. Touch it several times so that you leave a lot of fingerprints. Now try the different methods you consider for your sensor.
If you hold the glass in front of a window after cleaning, you will see every little smudge, much better than inside your camera. My guess: you will never want anything else than Magic Scotch tape anymore :) |
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08/31/2012 11:03:50 AM · #55 |
Originally posted by MistyMucky:
The only valid objection I heard about Scotch tape is that you could eventually peel off the top layer on your low-pass filter. In most cameras I believe this is a very thin anti-static layer made of ITO (same as on iPads & co). It is not something which you could see with optical instruments, which also means that the image quality of your camera will never be affected. Personally I do not find this a concern at all. |
Some cameras have an ITO (indium-tin oxide) coating, which by the way *is* an optical component of the filter (it's what rejects the infrared band). It is not a very hard material, and there have been a few reports of damage to ITO coatings after wiping them; damaged ITO coatings will be visible in the image. The original Canon 5D had some early problems with this, but I believe it was probably related to problems with deposition of the ITO. The ITO should not be susceptible to methanol (the main component of Eclipse). Nevertheless, they did come out with a less aggressive version of Eclipse for this coating.
There are other coatings used for infrared rejection that seem to be less susceptible to damage than ITO. I'm not sure what percentage of cameras still use ITO.
Originally posted by MistyMucky:
My opinion about Eclipse: totally over-priced and needlessly toxic. If I have to use a liquid cleaner inside my camera, I use isopropyl or ethyl alcohol. What I do not like with liquids is that when you have greasy residues on the low-pass filter, you spread them over the whole surface and you have to repeat the process several times. The evaporation residues come usually from the dirt, not the alcohol, therefore I found standard grades mostly OK to use. |
I tend to agree with you on the price of eclipse; that's the price we pay for the small bottle. You can buy a half-liter of equivalent material (see below) from a chemistry supply house for about $30 USD. As far as toxicity, methanol is pretty benign. I'd be cautious with prolonged exposure, but with the tiny amounts and short exposure time involved in sensor cleaning, there's really nothing to be worried about.
As far as residues, you absolutely need a very pure solvent or you will get residues on evaporation. The best available grades of methanol are typically around 5ppm residue after evaporation, which is low enough. Anything below 10ppm is probably sufficient. FWIW, you will not find isopropyl alcohol (2-propanol) that pure, it is far too hygroscopic; it also does not evaporate as fast as you want it to. Ethanol is a possibility, I believe it is the main component of the alternative Eclipse formulation. Because it's ethanol, however, it must be "denatured" to be sold; that involves adding other solvents to make it toxic and therefor undrinkable.
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08/31/2012 11:14:49 AM · #56 |
| Fritz, I'll have to look around for it. I suspect it has served its purpose and is no longer with us. |
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08/31/2012 12:03:48 PM · #57 |
Fritz, thanks for the interesting info on ITO.
Regarding alcohols, we do not quite agree. Methanol is certainly unproblematic in small doses, but I would never have it in the same house than kids! For cleaning purposes, I would consider it an advantage if isopropanol absorbs some water, it becomes a more universal cleaner. Why does it have to evaporate very fast? I did not notice an effect, but I would be interested in learning one. About purity: if you clean a dirty surface, then purity becomes far less relevant than when you clean a clean one, if you see what I mean. |
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08/31/2012 12:30:21 PM · #58 |
Originally posted by MistyMucky:
Fritz, thanks for the interesting info on ITO.
Regarding alcohols, we do not quite agree. Methanol is certainly unproblematic in small doses, but I would never have it in the same house than kids! For cleaning purposes, I would consider it an advantage if isopropanol absorbs some water, it becomes a more universal cleaner. Why does it have to evaporate very fast? I did not notice an effect, but I would be interested in learning one. About purity: if you clean a dirty surface, then purity becomes far less relevant than when you clean a clean one, if you see what I mean. |
Yes, you certainly want to keep any solvent (including ethanol or 2-propanol) out of reach of children.
The hygroscopic nature of 2-propanol is sort of an indirect issue. Because we're going to have it sitting around, it may eventually pick up enough water to become an problem. Fast evaporation is an advantage because the liquid has less time to pick up undesirables from the air and redeposit them on the surface. Bottom line, you *can* get 2-propanol with low enough residue to do a good job. It's just not a great solvent for removing greasy soils like lubricant spots, and it's really not significantly less toxic if consumed.
With regard to the need for a low-residue solvent, the amount of residue present in the solvent places a limit on how clean you can gt a surface. More residue in the solvent means more stuff left on the surface. We're not talking about particulate matter here, we're talking about dissolved solids. You don't want to deposit those on your sensor.
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08/31/2012 01:23:27 PM · #59 |
| I'm pretty sure you can eat 3M Scotch Tape without ill effect... ;) |
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08/31/2012 02:01:28 PM · #60 |
Originally posted by kirbic:
The hygroscopic nature of 2-propanol is sort of an indirect issue. Because we're going to have it sitting around, it may eventually pick up enough water to become an problem. |
I don't see why isopropanol would be specially hygroscopic. Even if it would be, it would absorb 12% water until it reaches the azeotrope, which would actually lower its boiling point. Therefore following your next theory, it would be beneficial and not problematic. This water would also be ultra pure as it is condensed.
Originally posted by kirbic:
Fast evaporation is an advantage because the liquid has less time to pick up undesirables from the air and redeposit them on the surface |
I guess you mean dust by undesirables? But what does it change if it goes on the alcohol before evaporation, or directly on the low-pass filter? The difference in evaporation time must be a couple of seconds. Btw, the inhouse cleaning solution from Canon seems to be 90% isopropanol and 10% water.
Originally posted by kirbic:
Bottom line, you *can* get 2-propanol with low enough residue to do a good job. It's just not a great solvent for removing greasy soils like lubricant spots, and it's really not significantly less toxic if consumed. |
You need less than 10g of methanol to become permanently blind. From the same dose of isopropanol you get probably a bad headache. That's the difference between a death skull or just a cross on the respective bottles...
Originally posted by kirbic:
We're not talking about particulate matter here, we're talking about dissolved solids. You don't want to deposit those on your sensor. |
96% ethanol for instance is distilled, hence there cannot be any dissolved solids in there, if handled properly. The rest is just water and other alcohols, no residues from these.
You really want to argue about this stuff with a chemist?
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08/31/2012 03:14:44 PM · #61 |
Originally posted by MistyMucky:
You really want to argue about this stuff with a chemist? |
You really want to argue about this with a process engineer? ;-)
Your statement that 96% ethanol for instance is distilled, hence there cannot be any dissolved solids in there... is is fallacious because it assumes the distillation process is perfect, which it certainly is not. There would be no need for specifications on reagent grade (and better) solvents for "residue after evaporation" if that were the case.
96% alcohols are not adequate for precision cleaning of optical surfaces. That's not to say they won't work at all, just that they are *far* from optimal.
With regard to your toxicity comparison, you are certainly correct in your statement. From a practical standpoint, both are a no-go with kids. We all have worse chemicals in our homes, including strong acids and bases. It's our responsibility to keep them secured.
Message edited by author 2012-08-31 15:15:19.
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08/31/2012 03:16:39 PM · #62 |
Originally posted by DrAchoo:
I'm pretty sure you can eat 3M Scotch Tape without ill effect... ;) |
:D
There is another solution: if one gets completely drunk on regular booze, the liver does not metabolise methanol anymore and it becomes harmless. But I guess one would not find the menu for mirror lock-up anymore after 10 beers. |
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08/31/2012 03:28:54 PM · #63 |
Originally posted by kirbic:
Because it's ethanol, however, it must be "denatured" to be sold; that involves adding other solvents to make it toxic and therefor undrinkable. |
Everclear is a real option. Get hammered and clean the camera.. (one for the swab, fourteen for me)... |
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09/02/2012 10:24:00 AM · #64 |
I've taught engineers and chemists who don't know how to use the stuff about differences in grades and applications, do i get to be called a bigger authority? rwar! regardless, why not...
I m worried about the residue from the tape, but i haven't tested it cause i m chicken. Far as decent grade alcohols, i can deal with that. I know the right grades of stuff is used in industry application for specific sensitive electronics cleaning. If i get the time, i ll call up a canon customer tech rep from my last camera fix and ask them how they go about it.
Ps: i know you guys are experienced, and if its not apparent, i m totally kidding around in my first sentence.
Message edited by author 2012-09-02 10:28:24. |
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