Won't hurt at all.

 

The shade actually doesn't matter for eye protection, regardless what a lot of people try to say. All properly maintained welding hoods provide 100% UV protection according to the manufacturers (quoted from OHS website https://ohsonline.com/Articles/2007/02/Preventing-Eye-Injuries-When-Welding.aspx?m=1&Page=3 ) and I'm pretty sure even when off, auto darkening hoods do also. Brightness is not what hurts your eyes. It's specific wavelengths of light in the low blue/UV and IR spectrums. Even clear lenses can provide 100% UV protection. The brightness level is only about comfort. Standard lenses are tinted green because green is the most relaxing color for your eyes. That's actually why night vision goggles are green. (I have over 500 hours on NVGs and the extensive training that accompanies it, which is why I happen to know a lot about light and eye safety).

Basically, if your lens isn't damaged in any way and light isn't leaking into your hood, you don't need to worry about hurting your eyes. Lens shade is all about what you are comfortable with and being able to see what you need to see. I've been welding over ten years in shade 9 without any ill effects.

 

Even clear lenses can provide 100% UV protection.

99.9ish%, but that tiny fraction of a percent is still a big deal with all the UV coming out of a welding arc.
Anyway, it is completely possible to damage your eyes with a bright enough visible light source, even if the UV and IR are completely blocked. And a welding arc is plenty of bright enough to hurt your eyes through a clear lens.

As for a shade 9, yeah, that should be fine if you're comfortable with it. If you see spots when you break the arc, perhaps it's not dark enough for you.
I tend to use 9, 10 and 11, depending on what I'm welding (aluminum calls for a darker shade than steel), and the current involved.

 

I use shade10 for just about everything, rarely change it.

 

Thank you all for your answers and help.

 

Hours was in reference to the florescent lights in excess of 8 hours and I believe was on horses, not exactly humans, but still mammilian, and I got that info from some study that was done. It was also pertaining specifically to photochemical damage, not photothermal. The retina actually does not have pain receptors, and any "pain" is a psychological response.

What I'm basically getting at is there is really nothing to worry about when using proper welding lenses, regardless of the shade. But I hear a lot of welders try to tell me my eyes will get damaged for using shade 9 all the time.

 

What I'm basically getting at is there is really nothing to worry about when using proper welding lenses, regardless of the shade. But I hear a lot of welders try to tell me my eyes will get damaged for using shade 9 all the time.

Yep, 100% agreed. And adding extra light to the party in the form of work lights, even if they're so bright that it appears as bright as daylight from behind the mask, won't hurt at all.

Shade 9 is perfectly safe. I only use darker shades, because I'll see spots, which impacts my view of the puddle, in brighter situations.

 

Yeah whatever light is added is nothing compared to the arc. I may actually need to step up to shade 10 because I've been using a 9100xx hood, and it fell from scaffold and cracked the lens so I upgraded to the 9100xxi "tru view", and it's ridiculously clear. It's like using a gold fixed lens.

 

Some people have very sensitive eyes. I do not, but I know people who do, so I guess that if you are one of those people the reflection of the Sun on a piece of metal might give you a headache and/or a Skotoma. If looking directly at the Sun does that to you and causes discomfort afterwards, then I would say it is very likely. So when you are outside, it would be better have sunglasses on before you put on your welding helmet.

With a Welding Helmet on you would be fine unless you are in a spaceship and ridiculously close to the Sun.

If you get an Auto-Darkening helmet you will have the ability to adjust the shade setting between shades ~10-13.