Moss, Thanks for the URL, good info. Tends to disagree with some well intentioned good ole boys but...oh well.
There is a considerable spread in response times of helmets. I think I recall seeing times as short as 1/25000 sec, a fourtieth of a milisecond commonly but there are probably even faster ones.
Anyway, modern thought is that cumulative UV damage from normal life experience is BAD and promotes cataracts and whatever so we should wear protection. UV from welding is intense and broad spectrum and is extremely bad.
You don't get FLASHED the same through an auto lense as naked eye. Good lenses stop virtually all IR and UV even when not turned on. What comes through is not enough to be a hazard.
It would be appropriate to be concerned with cumulative effects of a naked arc with its UV and full spectrum even if accumulated a milisecond at a time over a protracted carreer. (Like when your peripheral vision gets hit when someone strikes or when with unprotected eyes you look at the blue glow, even with the actual arc obstructed.
Not the case with auto lense since it stops virtually all IR and UV. Irrespective of your personal flicker rate, if you can't see the light (with no UV in it) I don't think there is evidence of damage adding up any more than exposing your eyes to regular room lighting with no UV. Your eyes take in lots more light in a few minutes in a sunlit venue than you will get through an A-D lense during a work day.
The amount of light you are normally exposed to adds up to way more than a series of milisecond blinks. If it were going to blind you you would be blinded in a matter of hours since each second is 1000 miliseconds so one minute is 60,000 "FLASHES". 360,000 flashes per hour or 1.4 milion FLASHES in 4 hours and most of us keep our eyes open in fairly bright light for several hours a day, usually more than 4.
There is a definite difference between lots of flashes of visible light, so brief as to be invisible, and UV-IR exposure. It would seem that casual exposure in a shop to UV while you are not wearing protection would be more of a hazard than the filtered light coming in brief pulses through an A-D lense. If the light coming through the lense is not dangerous due to IR or UV and is so brief as to not be noticed, is it going to add up to something worse than normal illumination? Doesn't seem that way. Seems the more reallistic but apparently unappreciated threat to long term vision health is casual unprotected exposure to arc rays.
The medical community has established the deleterious effects of your accumulative exposure to environmental UV and basically says less is better. Arc rays are worse than environmental UV so those working around arc welders should wear eye protection. Unfortunately most welders I have seen in the workplace do not.
Eyes are important and it is best to err on the side of safety and caution but there are limits before you get into superstition and ignorance.
I too have a quite high flicker rate. I do not perceive a flash of light before the lense darkens. Neither stick nor MIG or TIG have arc startup characteristics of a steep leading edge square wave. Although the user may not perceive the "ramp up" of arc intensity, there is one. The arc doesn't start instantaneously. As the fill metal, base metal (workpiece) and the involved air and shielding gases heat up (plasma conditions) the conductivity becomes quite different from the initial discharge, much more intense. I'm not sure if this matters but the topic was breached earlier. So in that vein; a functional A-D lense will be dark before the arc reaches full output.
I do not in any way intend to lower anyones impression of the dangers of exposure to unfiltered arc rays. Eyes are precious, protect them.
About welding shades; All approved welding glass will filter the UV. The shade is selected so you can see what you are doing comfortably. If you go extra dark, supposedly for safety, to the point you can't clearly see the welding puddle and adjacent base metal you don't "GET IT." If you use too light a shade it won't give you extra UV. An arc can be extremely intense in the visible spectrum, brighter than the sun. Too light of a shade is like being in the desert or at the beach without sufficient sunglasses.
Pick a shade or adjust a variable A-D for the work at hand. One size DOES NOT FIT ALL! BIG ROD at BIG amps makes for lots of light compared to 3/32 or lighter at a few amps.
If you can't see what you are doing you wont be effective AND aren't safer than with an appropriate shade. Remember, don't look at the arc, look at the puddle! Can you see it well enough?
The recommendations for my 40 amp plasma cutter is shade 4 or 5 which is about like sun glasses. I chose 5 to cover the top end but my eyes dark adapt well fairly quickly so I don't need shade 4 for light amp work. In my opinion my A-D lense won't turn down enough as when doing low amp MIG with with wire feed gun and flux core I can barely see what I am doing and part of the time go by Braile. It claims to vary from 9-13. Everyone's eyes are different. I used to attract attention because my pupils dialate so large at night. I was thought drunk or on drugs because of it but the real deal was I had superlative night vision and still do, decades later, after welding with A-D for well over a decade.
I am extremely concerned with my eyes as I am an amature photographer, astrophotographer and astronomer. I am aware of my vision and concerned to conserve it.
If I have "missed the boat" on any of these topics, please do not be bashful, tell me. This is important stuff.
About HF or other cheap tools: Ryobi 14 inch abrasive saws aren't indestrucable either. I have three dead ones right now. OK to be fare I dropped one and broke the cheap casting and one was given to me inop. I was cutting HD 4 1/2 inch pipe to make a guard to keep friends from hitting my heat pump when parking when it literally burned up. I wasn't being particularly abusive and suddenly flames shot out of the motor vents about 12-14 inches. I released the trigger switch and placed my gloved hand over the vents to smother the fire. When I removed my hand it flashed back into flames and I covered it again, LONGER. It flashed again! I covered it for at least 10 seconds and it didn't flame again.
Maybe I can put enough pieces together to make one out of the carcasses I have. I have a nice DeWalt on a wheeled cart for shop use but used the Ryobi for portable outside or from back of a truck jobs.
WIth HF tools there is a good news bad news story: Good news you can get a cheap replacement warranty and they will exchange the tool for another one just like it if it fails, FOR FREE. The bad news is you might spend a lot of time returning the tools but they seem to be holding up better than say 10-15 years ago. I needed a high speed corded drill for pocket screw jig duty and HF fit my idea of price for the limited use I would get. I, of course, ended up using it for other tasks but so far it works as expected. NOt very HD but fast, what I needed. (Pocket screw step drills last much better if used at high RPM as per manufacturer.)
Update. Just saw helmet on eBay. 1/25,000 second darkening, defaults on malfunction to shade 16, adjusts to shade 9-13 or shade 4, solar powered, UV % of transmittance is 3.4 X 10-8 (that is 0.000000034%) and it has large view lense. This is not unique or unusual, but good.
Pat
