Reply to thread

Message: <blockquote data-quote="guywhofishes" data-source="post: 181940" data-attributes="member: 337"><p>you can't imagine how little light shade number 14 filter glass (the recommended sun viewing shade number) lets into your eye: </p><p></p><p><strong>What do the numbers in welder's glass specifications mean (e.g., #14)?</strong></p><p></p><p><span style="color: #000000"><span style="font-family: 'Arial'">The shade number (SN for short) is based on the optical density of the glass in the visible region. If the fractional transmission of light through the glass is T, then</span></span></p><p> OD = -log T</p><p> SN = 1 + (7/3) OD</p><p></p><p><span style="color: #000000"><span style="font-family: 'Arial'">Consider, for example, a filter that blocks 99.9% of the visible. T = 0.001 and hence OD = 3, and SN = 1 + (7/3)*3 = 8. This would thus be typical for a #8 welder's glass.</span></span></p><p><span style="color: #000000"><span style="font-family: 'Arial'">If you plug SN=14 into the formula above, you can show that the OD is 39/7, or 5.57... A #14 welder's glass transmits about 3 millionths of the light hitting it.</span></span></p><p><span style="color: #000000"><span style="font-family: 'Arial'">Note that this formula <em>only</em> applies to transmission in the visible; for IR and UV the specifications are a little more complicated, and not given by a nice neat formula like this. In the US the requirements for welders' glasses are given in the ANSI publication listed in the references. In general the tolerances for UV and IR are not quite as strict as those in the visible, which is part of the reason astronomers recommend the darkest shades of welders' glass for solar viewing.</span></span></p></blockquote><p></p>

Verification: What is the most common fish caught on this site?

Recent Posts

MN walleye possession Limits
- Latest: 1lessdog
- 11 minutes ago
R
Outdoor photo request
- Latest: riverview
- 40 minutes ago
S
Property Tax Credit
- Latest: snow2
- Today at 2:10 PM
StrikeMaster Maven-40v
- Latest: Sluggo
- Today at 12:32 PM
Beef prices going up????
- Latest: Davy Crockett
- Today at 11:10 AM
Look at the size of that deer
- Latest: SDMF
- Today at 9:59 AM
NFL News (Vikings)
- Latest: Rowdie
- Today at 8:47 AM
MN Wolves
- Latest: SDMF
- Today at 8:44 AM
Wolf Hunting?
- Latest: Obi-Wan
- Today at 6:04 AM
Squirrel trapping?
- Latest: Obi-Wan
- Yesterday at 9:58 PM
R
Accuphy Ping Live Sonar
- Latest: riverview
- Yesterday at 8:19 PM
Remote camera options
- Latest: Wirehair
- Yesterday at 7:43 PM
Batten down the hatches!
- Latest: lunkerslayer
- Yesterday at 6:48 PM
OAHE Ice 25/26
- Latest: Kurtr
- Yesterday at 1:05 PM
Satellite Internet
- Latest: grantfurness
- Wednesday at 10:11 PM
R
Any ice reports?
- Latest: riverview
- Wednesday at 9:25 PM
Weather 6/20/25
- Latest: Jiffy
- Wednesday at 7:57 PM
Alkaline lake ice conditions?
- Latest: NDSportsman
- Wednesday at 2:55 PM
N
ION gen2 8"
- Latest: ndrivrrat
- Tuesday at 5:43 PM
Four legged tax deduction
- Latest: luvcatchingbass
- Tuesday at 4:51 PM
I HATE coyotes!!!!
- Latest: luvcatchingbass
- Tuesday at 4:43 PM
Wolves at J Clark Sawyer
- Latest: Davy Crockett
- Tuesday at 11:08 AM
W
Which one you did this?
- Latest: walleyeman_1875
- Monday at 12:17 PM

Friends of NDA

Top Bottom