How do you know when it affects image quality before that happens?
Lens cleaning
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By looking at the image or measuring MTF.
Is there an alternative to Kimwipes? I don't live in North Korea...
My point is I don't want to wait until the image is affected. Then it's too late. So how do you determine before the image is affected that it's time to clean the lens?
*my* point is that you don’t clean them unless you absolutely need to, as cleaning optics is the most damaging purposeful thing you can do.
Instead, practice preventative measures. If you do, then you will never need to clean them. Use filters and lens caps appropriately, store optics so as not to induce fungal growth, keep fingers off the glass, don’t look at the isolated specks of dust if dust on optics bother you, etc. This is a much better mindset to have.
The primary mirror on my 15 yr old telescope looks like it has sat out much of its life... which it has and it also survived a moving van fire. The tube just stopped smelling like smoke, and I noticed it has cobwebs and an eight-legged resident perched, ironically, near one of the spider veins. Yet it still images nebulae and galaxies perfectly fine. After 15 years of accumulated stuff on the mirror, I’m only now considering removing to wash in mild soap and water. I likely won’t tho, as the surface itself has not been damaged but rather is just covered in dust and stuff. I would bet a bottle of mead it’s dirtier than any lens readers of this thread use for photography. The analysis will tell you that 13% clear aperture area obscuration begins to impact the MTF. That’s a lot of dust. Scatter impacting contrast is the other mode, and I haven’t seen it yet on my telescope where its use in viewing dim objects in space is very sensitive to contrast change.
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For what it's worth, I was told many years ago by Leitz repair manager that they used pure ammonia ( not the stuff with cleanings agents added) along with a gentle touch. For handiness, I generally use Tiffen lens cleaner from my cinema camera shop. Simply breathing on lens a very gently brushing with a cotton swab usually does the job.
Best protection, as already noted, a UV filter.
Best protection, as already noted, a UV filter.
In fairness, the aluminum reflective coating on a telescope mirror is *much* more fragile than modern lens coatings, unless it's overcoated (silicon monoxide still isn't anything like as hard as glass, but it's a good bit better than pure aluminum). That said, the coatings on a lens aren't as hard as the glass, either, and optical glasses are generally some of the softest glasses you'll find.
BTW, if you are considering cleaning your telescope mirror, I'd suggest looking into collodion cleaning. Yes, that's the same collodion (without the halide salts) that you'd use for wet plate photography; it's poured coated onto the mirror surface (ideally, with no run-over onto the edges, to minimize the possibility of it sticking too well), and allowed to dry completely, then carefully peeled off (scotch tape makes a good way to start it, then it'll usually come off in a sheet). It'll take the dirt with it, and won't damage the aluminum.
I've done this using SIG Nitrate Dope (for model airplanes) on the mirror of a cheap Christmas reflector, and it worked (including no detectable damage to the coating); I'm sure it would be better with higher nitrogen content collodion.
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If I want a lens to be perfectly clean I use ROR and Kimwipes. For the interior of the lens I use Opticlean if the lens is worth it. It is called something else now, but it is painted on then let dry and peeled off. If you want pristine then it is a great way to go. Last time I checked it cost a fortune though.
Can I use this Kimwipe instead of microfiber cloth on my lens or plastic eyeglasses with Zeiss lens cleaner?
Also, I've noticed that with the pollution in the air, glass will take on a slight coating that brightens up with the Zeiss cleaning or even a breathe cleaned with the lens cleaning microfiber cloth. Does this "haze" lower contrast or have other effects?
I don’t touch optical surfaces with microfiber cloth. They are too good at trapping dirt particles that will scratch the glass or coating. Kimwipes are lint-free, non-abrasive, and environmentally friendly, bio-degradeable, and (subtle but important) not supposed to be used for more than a wipe or two. Wipe and toss... your lenses are worth way more than a piece of tissue.
Gentle, light puffs of canned air to remove loose lint and dirt (canned air is cleaner than your slobber from breathing on it). fold up the tissue and apply the cleaner to the tissue. Then, without applying pressure, deag the tissue across the surface. For larger glass I start from center and wipe towards edge. If using Windex, wipe off with a dry tissue in the same manner. Toss both and repeat with clean tissue as necessary. Don’t apply pressure: let the solvent do its job.
Protect your lens with a filter on the front to avoid environment-induced haze. Haze on internal surfaces is from outgassing due to manufacturer’s poor choice of lubricants. You only have two options in that case: don’t reward bad design behavior by avoiding those lenses, or vacuum-cycle the lens assembly for a day or two at a slightly elevated temperature to pull out the volatiles.
I clean only with what I listed above. I’m a professional, and prefer not to risk damage to optics with unproven or industry-rejected methods. The mirror will clean up fine with a mild soap and warm water bath.. By “fine”, I mean “incur the least amount of surface damage with the least risk of incurring scratches”.
It doesn’t matter how hard or soft the coating or glass is... every time you wipe or touch the surface you’re removing material. Harder glasses simply take longer to wear through (coating materials and optical glasses are slightly soluble, btw..more or less so depending on acidity/alkalinity of your solutions). Nanometers of thickness count..especially for coatings and that’s not a lot of material. This aside from the risk of scratches.
so yeah..don’t clean your lenses if you can help it. Keep them from getting to that point in the first place.
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Worth noting that bare aluminum coating (without overcoat) is also susceptible to attack by any alkali, including soaps and most detergents, or any chloride in solution -- and though not a nanometer level of thinness, typical mirror coatings are a couple micro-inches thick (well, okay, that's a few tens of nanometers). Then again, there's an expectation in the amateur astronomy community that you'll need to recoat a mirror periodically -- used to be, with silver, every 3-5 years, but aluminum lasts a bit better than that (downside is, it can't be applied by most amateurs; silver can, by anyone competent to mix developers or emulsions).
Error #143245.78
RESPONSE TOO LITERAL.
I have a weird sense of humor. Blatantly literal responses to obvious jokes is one aspect.
Right. This particular mirror is a special sixth-order aluminized coating with protective overcoat (google VC200L). In any case, as mentioned I haven't chosen to clean it in 15 years because of the risk. Screw up that coating and there's only one place in the world that can re-coat it.
Yep. And a plain aluminum coating applied in a bell jar by a local telescope maker would lose a percent or so of reflectivity...
It would be a little less durable, though.BTW, that's how my (self-made) 8" telescope mirror was aluminized. In 1998. Last time I had it out (defying the North Carolina weather, and before my current job that precludes being up late enough to bother) it still performed just fine. If/when I need to recoat it, I'll probably switch to silver, because I can do it myself.
I had a similar problem a few years ago.
Seems like LOTS of people do.
I think the biggest problem... For Me... was those PED cloths, or whatever those micro fiber type tissues are called.
A few of our members recommended the Kim-Wipe lens tissues. As soon as i used those, all of me Streak/Smear troubles vanished.
Barring something really bad, it does not seem to matter what cleaner i use...be it something "Professional" or just a home made remedy of distilled water and 91% alc.
Seems like LOTS of people do.
I think the biggest problem... For Me... was those PED cloths, or whatever those micro fiber type tissues are called.
A few of our members recommended the Kim-Wipe lens tissues. As soon as i used those, all of me Streak/Smear troubles vanished.
Barring something really bad, it does not seem to matter what cleaner i use...be it something "Professional" or just a home made remedy of distilled water and 91% alc.
I have clear glass multi-coated protection filters on all my lenses, that I clean occasionally, I very rarely need to clean my actual lenses because the front elements don't get dirty, and generally only if the rear elements get a fingerprint on them from me handling them while changing lenses do I need to clean them.
Years ago you could find lens cleaner in a little red bottle w/ a white cap in drugstores. It was hung on a rack in a clear blister package w/ some some lens tissue. Remember them? I must have cleaned 100 lenses w/ that package over the course of many years, and whatever was in that little bottle dried w/o a mark and the lens tissue never scratched anything. I haven't found a good replacement since then, and dislike the microfiber cloths.
A lot of those 100 lenses had optical and other issues. Haze or separation at the edges was OK, but haze that covered more of the lens surface did cause flare even w/ a hood. Scratches and even big nicks in the front optics didn't do anything as long as I used a lens hood, but you had to paint the seriously deep ones w/ flat black paint.
A lot of those 100 lenses had optical and other issues. Haze or separation at the edges was OK, but haze that covered more of the lens surface did cause flare even w/ a hood. Scratches and even big nicks in the front optics didn't do anything as long as I used a lens hood, but you had to paint the seriously deep ones w/ flat black paint.
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What is the feeling/experience with lens pens? Over in the digital world, people swear by them, but I haven't seem many people in the film world mention them. Basically they have a brush on one end to brush of any particulate matter that might scratch the lens when you wipe it, then the other end has a carbon pad that you use to actually clean the surface (and it’s used dry, without cleaners or solvents.)
I shoot better when my lens is clean.
Seems easier to just clean the smudge off. In any case, what good is waiting until you see it affecting your images. It's too late then.
What about eyeglasses? I've found they need to be cleaned daily. I use Zeiss lens cleaner with either Kimtech or eyeglass cloth. If they're really bad, I;ll wash them first in Dawn dishwash detergent that cuts grease with lots of warm water from the faucet. Then I spray them with the Zeiss lens cleaner and use the eyeglass cloth or Kimtech.
As an aside, if eyeglasses get that haze or slight film over them, so should lenses. Just because you don't see it (you're not looking through the lens), doesn't mean it isn't there effecting the photo image.
As an aside, if eyeglasses get that haze or slight film over them, so should lenses. Just because you don't see it (you're not looking through the lens), doesn't mean it isn't there effecting the photo image.
Eyeglasses (at least mine) pick up hundreds of times as much junk as camera lenses. After all, I don't wear camera lenses on my face, where they're subject to fingerprints from constant adjustment, dandruff, skin oils, eyelashes, and anything they intercept that would otherwise have gone in my eye. Most of them, additionally, have anti-scratch coatings and aren't expected to last more than a couple years in service.
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