Equations in my OPF posts

Doug Kerr · Aug 4, 2026

Some of you may have watched (perhaps in horror) the verbose thread in which Ted Cousins and I discussed the challenges of including mathematical equations (and formulas and expressions) in OPF posts.

It seems that there is no ideal, universal way to do that (at least, findable by us).

As for me, if and when in future I need to include such creatures in an OPF post, I will probably in general do it by including in the post a "picture" of the creatures. There can be various shortcomings to this, but it's all I've got.

So I close with this, the formula for the probability density function of the standard distribution, inserted here as its "picture", at what is, as seen here, a "nice" size:

There is no telling how that will come out at your end; this is the only end I have here.

I would be pleased to hear from other members how this looks at their end.

Best regards,

Doug

Jerome Marot · Aug 5, 2026

At my end, the equation is perfectly legible and at a size similar to the text.

I am using the "lights on" version of the site. Obviously, if I press "lights out", the text becomes negative but the equation does not.

Ted Cousins · Aug 5, 2026

Doug Kerr said:
Some of you may have watched (perhaps in horror) the verbose thread in which Ted Cousins and I discussed the challenges of including mathematical equations (and formulas and expressions) in OPF posts.

It seems that there is no ideal, universal way to do that (at least, findable by us).

As for me, if and when in future I need to include such creatures in an OPF post, I will probably in general do it by including in the post a "picture" of the creatures. There can be various shortcomings to this, but it's all I've got.

So I close with this, the formula for the probability density function of the standard distribution, inserted here as its "picture", at what is, as seen here, a "nice" size:

View attachment 14358
There is no telling how that will come out at your end; this is the only end I have here.

I would be pleased to hear from other members how this looks at their end.

Best regards,

Doug

Your BBcode says:

Code:

[ATTACH type="full" width="163px" alt="1785867049434.png"]14358[/ATTACH]

... and 163 screen px is how it looks on my screen in your post.

i.e. Comes out 163 screen px width in your post on my monitor.

Here's how the original looks without the "width" attribute:

View attachment 14358

The 447x133 data px attachment

Code:

https://openphotographyforums.com/forums/attachments/1785867049434-png.14358/

as an image without attributes using BBcode:

Code:

[img]https://openphotographyforums.com/forums/attachments/1785867049434-png.14358/[/img]

Seems zoomed in on my monitor. I suspect CSS ...

CSS says "max-width" ... and often, when I post images here, they come out bigger.

https://openphotographyforums.com/f...05&k=7d177d13cfd70a6ebfb902b31ba3956560554004

Maybe of interest: https://blog.saeloun.com/2024/07/22/css-units/

Ted Cousins · Aug 5, 2026

Ted Cousins said:
Seems zoomed in on my monitor. I suspect CSS ...

CSS says "max-width" ... and often, when I post images here, they come out bigger.

https://openphotographyforums.com/f...05&k=7d177d13cfd70a6ebfb902b31ba3956560554004

Also found this right-clicking on this post and selecting view-source

https://openphotographyforums.com/forums/css.php?css=public%3Aattachments.less%2Cpublic%3Abb_code.less%2Cpublic%3Aeditor.less%2Cpublic%3Alightbox.less%2Cpublic%3Amessage.less%2Cpublic%3Ashare_controls.less%2Cpublic%3Aextra.less&s=6&l=1&d=1749225105&k=f347c2ad4437ad886602d73fbb9ca9d3de39e270

Couldn't find the image in the CSS though ..

I got the CSS link by using FireFox's right-click Inspect(Q) with the image selected. Not real easy to follow for me ...

Ted Cousins · Aug 5, 2026

Ted Cousins said:
I got the CSS by using FireFox's right-click Inspect(Q) with the image selected. Not real easy to follow for me ...

I think it means 100% of whatever content-box the "bbImage" is contained in.

"auto" means correct aspect-ratio ...

Doug Kerr · Aug 5, 2026

Hi, Ted,

Ted Cousins said:
I think it means 100% of whatever content-box the "bbImage" is contained in.

"auto" means correct aspect-ratio ...

Ah.

I have not even thought about CSSs.

Best regards,

Doug

Doug Kerr · Aug 5, 2026

Hi Ted,

In the next post I will show come of the code that appears here when I am looking at this post.

The top phrase below is just regular text.

It appears below as an inserted picture captured from the line above, with the displayh size set so the two strings are of comparable size as seen here.

The quick brown fox.

Best regards,

Doug

Doug Kerr · Aug 5, 2026

Hi, Ted,

Here is the HTML code, as the OPF page is seen here, that produced the second "phrase" (via its picture)in the prior post:

<img src="https://openphotographyforums.com/forums/attachments/1785867049434-png.14358/"
data-url=""
class="bbImage"
data-zoom-target="1"
style="width: 163px"
alt="1785867049434.png"
title="1785867049434.png"
width="447" height="133" loading="lazy" />

Note that the PNG file was not generated by me but rather was generated by the OPF software here from an image I Pasted in from the Windows clipboard.

It looks as of the style="width" value controls the display width of the picture. It is the width in pixels of that object as seen on screen here with the browser zoomage set to a certain level. (That is not the "default" zoomage level that we can invoke in my browser with Ctrl-0.)

The width and height values at the end are seemingly those of the PNG-file image.

Best regards,

Doug

Doug Kerr · Aug 5, 2026

Hi, Ted,

For what it is worth, here is a screen shot of those two phrases (the first one in actual body text, the second a picture) with the browser "zoomage" set at what I will call "step 4" (out of 14). Its display size has not been adjusted.

Here is a screen shot with the browser zoomage set to "step 6":

Best regards,

Doug

Ted Cousins · Aug 5, 2026

Doug Kerr said:
Hi, Ted,

Here is the HTML code, as the OPF page is seen here, that produced the second "phrase" (via its picture)in the prior post:

<img src="https://openphotographyforums.com/forums/attachments/1785867049434-png.14358/"
data-url=""
class="bbImage"
data-zoom-target="1"
style="width: 163px"
alt="1785867049434.png"
title="1785867049434.png"
width="447" height="133" loading="lazy" />

Note that the PNG file was not generated by me but rather was generated by the OPF software here from an image I Pasted in from the Windows clipboard.

It looks as of the style="width" value controls the display width of the picture. It is the width in pixels of that object as seen on screen here with the browser zoomage set to a certain level. (That is not the "default" zoomage level that we can invoke in my browser with Ctrl-0.)

The width and height values at the end are seemingly those of the PNG-file image.

Best regards,

Doug

Here's what I get from FireFox Right-Click view-source

Code:

&lt;img src=&quot;<a href="https://openphotographyforums.com/forums/view-source%3Ahttps%3A//openphotographyforums.com/forums/attachments/1785867049434-png.14358/" class="link link--internal" data-proxy-href="/forums/proxy.php?link=https%3A%2F%2Fopenphotographyforums.com%2Fforums%2Fview-source%253Ahttps%253A%2F%2Fopenphotographyforums.com%2Fforums%2Fattachments%2F1785867049434-png.14358%2F&amp;hash=7ecb6fb716b5eeccefea2e2fcd5fc420">https://openphotographyforums.com/forums/attachments/1785867049434-png.14358/</a>&quot;<br />
data-url=&quot;&quot;<br />
class=&quot;bbImage&quot;<br />
data-zoom-target=&quot;1&quot;<br />
style=&quot;width: 163px&quot;<br />
alt=&quot;1785867049434.png&quot;<br />
title=&quot;1785867049434.png&quot;<br />
width=&quot;447&quot; height=&quot;133&quot; loading=&quot;lazy&quot; /&gt;<br />
<br />

Interesting to compare formats

Doug Kerr · Aug 5, 2026

Hi, Ted,

Ted Cousins said:
Here's what I get from FireFox Right-Click view-source

<snip>

Interesting to compare formats

Indeed!

The main difference seems to be the recoding of quoted literals in the code as you see it.

Thanks.

Best regards,

Doug

Doug Kerr · Saturday at 2:02 PM

As can be seen in some other threads on this site, there is some question as to, when I put picture of an equation (or formula) in a post, whether its size (relative to the size of the body text) will appear to all viewers as it does to me.

The situation in that regard is still unclear.

And of course when I "size" the picture of an equation in a post there is no magical typographical criterion that guides me. I make it the size (as seen here) that seems to me at the time to be reasonable. My main objective is readability.

Best regards,

Doug

Doug Kerr · Monday at 8:42 PM

Learned journals and other serious technical publications have an elaborate set of "styles" that govern, among other things, how equations and formulas should be arranged, and at what size they will be included in articles.

And in fact for the technical articles I publish on my site, The Pumpkin, there are certain norms that I follow (some of them of accidental origin!).

But essays written as OPF posts, possibly quite technical, and occasionally including formulas and such, are not any of those. For one thing, a post does not presume a fixed page layout as seen by the "viewers", even as to the text itself.

So when I write a post that includes one or more formulas, I make them, as seen here, have an arbitrary size, which looks nice here. There is no plan nor consistency to this.

So I might put this formula in a post like this:

or like this:

and I don't really know for sure how either will come out at your end.

Best regards,

Doug

Ted Cousins · Tuesday at 12:23 PM

Just for laughs ... Unicode/BBcode equation ...

N²⟋t = LᐧS⟋K

Would be nice but can't set text background color in OPF

OPF HTML:
<div class="bbWrapper"><div style="text-align: center">Unicode/BBcode equation ... just for laughs ...</div><br>
<div style="text-align: center"><span style="font-family: 'Arial'"><span style="font-size: 18px"><span style="color: red">N²⟋t = LᐧS⟋K</span></span></span></div><br>
Would be nice but can't set text background color in OPF</div>

Doug Kerr · Tuesday at 3:38 PM

Hi, Ted,

Ted Cousins said:
Unicode/BBcode equation ... just for laughs ...

N²⟋t = LᐧS⟋K

Would be nice but can't set text background color in OPF

OPF HTML:
<div class="bbWrapper"><div style="text-align: center">Unicode/BBcode equation ... just for laughs ...</div><br>
<div style="text-align: center"><span style="font-family: 'Arial'"><span style="font-size: 18px"><span style="color: red">N²⟋t = LᐧS⟋K</span></span></span></div><br>
Would be nice but can't set text background color in OPF</div>

Interesting exercise. Nicely done.

I guess the formula intended to be shown is:

N²/t=LᐧS/K

and something went wrong with the encoding of the forward slashes (virgules). (They show up here as code 00, seemingly a replacement for a disallowed character code someplace along the way.)

In any case, the main player looks like this here:

Best regards,

Doug

Ted Cousins · Tuesday at 4:01 PM

Doug Kerr said:
Hi, Ted,

Interesting exercise. Nicely done.

I guess the formula intended to be shown is:

N²/t=LᐧS/K

and something went wrong with the encoding of the forward slashes (virgules). (They show up here as code 00, seemingly a replacement for a disallowed character code someplace along the way.)

In any case, the main player looks like this here:

View attachment 14389

Best regards,

Doug

They are UniCode U+27CB 'Mathematical Rising Diagonal' which look as such on my monitor but not on yours ... ho hum ...

On my screen:

Doug Kerr · Tuesday at 7:20 PM

Hi, Ted,

Ted Cousins said:
They are UniCode U+27CB 'Mathematical Rising Diagonal' . . .

Sounds like a good choice

Ted Cousins said:
. . . which look as such on my monitor but not on yours ... ho hum ...

No doubt a character set limitation in whatever typeface is invoked here! (Many of my typefaces are old and very limited in their provision of Unicode-only characters.)

Interesting that is has already been substituted (with "00"") in the code you sent me.

Ted Cousins said:
On my screen:

View attachment 14390

There are so many wrinkles to this!

Thanks for the info.

Best regards,

Doug

Doug Kerr · Tuesday at 7:51 PM

Hi, Ted,

I have the feeling that I may have no "font" here that includes U-27CB.

If I use my tool for "creating" a Unicode character from its hex codepoint ID, and do that in MS Word, thinking that it will find that character in some "font" that it knows (or knows how to fake it), it fails.

Best regards,

Doug

Doug Kerr · Tuesday at 8:05 PM

Hi, Ted,

Well, for what it's worth I installed the Symbola "font", which was reported as including U+CB27, and indeed it does (as seen on the Word character map).

And I am able to make MS Word put it up (but all my ways of doing that do not work).

Best regards,

Doug

Ted Cousins · Tuesday at 8:19 PM

Doug Kerr said:
Hi, Tedm

Sounds like a good choice

No doubt a character set limitation in whatever typeface is invoked here! (Many of my typefaces are old and very limited in their provision of Unicode-only characters.)

Interesting that is has already been substituted (with "00"") in the code you sent me.

There are so many wrinkles to this!

Thanks for the info.

Best regards,

Doug

Doug Kerr said:
Hi, Ted,

Well, for what it's worth I installed the Symbola "font", which was reported as including U+CB27, and indeed it does (as seen on the Word character map).

And I am able to make MS Word put it up (but all my ways of doing that do not work).

Best regards,

Doug

Interesting to hear and, as a result, I now intend to use a regular text forward slash in future for that character, hopefully making the string more readable to more people.

I use https://www.compart.com/en/unicode/search?q=math#characters to find math stuff and it does not let me search by font-family ...

Doug Kerr · Tuesday at 10:35 PM

Hi, Ted,

Ted Cousins said:
Interesting to hear and, as a result, I now intend to use a regular text forward slash in future for that character, hopefully making the string more readable to more people.

Probably a good step.

t/(N^2)=K/(LS)

Actually if we believe in the rules of precedence of operations, this is OK:

t/N^2=K/(LS)

but this isn't:

t/N^2=K/LS

Best regards,

Doug

Doug Kerr · Tuesday at 10:53 PM

Hi, Ted,

for what it's worth, MathMagic Personal, starting with this formula:

when asked, made this "ASCII Math" string:

( t )/( N ^2) = ( K )/( LS )

Many of the spaces there are gratuitous, and of course the parenthecation is "completely foolproof". (I might have almost done the same.)

Actually, MathMagic Lite (the free one) would do the same.

Another curiosity either of these will produce is this:

fraction t over N squared , equals fraction K over LS

That is intended to be read by a text-to-speech facility.

Best regards,

Doug

Ted Cousins · Wednesday at 5:34 PM

Doug Kerr said:
Hi, Ted,

for what it's worth, MathMagic Personal, starting with this formula:

View attachment 14392

when asked, made this "ASCII Math" string:

( t )/( N ^2) = ( K )/( LS )

Many of the spaces there are gratuitous, and of course the parenthecation is "completely foolproof". (I might have almost done the same.)

Actually, MathMagic Lite (the free one) would do the same.

Another curiosity either of these will produce is this:

fraction t over N squared , equals fraction K over LS

That is intended to be read by a text-to-speech facility.

Best regards,

Doug

Interesting. I tend to use the other-way-up equation, although you seem to favor the above ...

... AI otherwise

Google said:
Summary of Formulas
To map everything out sequentially:
Camera Settings: Calculate EV via \(EV = \log_2 (N^2 / t)\).
Reflected Light (B): Calculate required EV via \(EV = \log_2 (B \cdot S / K)\).
Incident Light (E): Calculate required EV via \(EV = \log_2 (E \cdot S / C)\).

Doug Kerr · Wednesday at 5:40 PM

Hi, Ted,

Ted Cousins said:
Interesting. I tend to use the other-way-up equation, although you seem to favor the above ...

I use it both ways up depending on the context.

But most often I cite it in the form with t on the top, since then the left side is the "photographic exposure" to which the camera is to be set. (That is a parameter that increases with "increased exposure", which seems sensible.)

Best regards,

Doug

Ted Cousins · Wednesday at 5:58 PM

Ted Cousins said:
Interesting. I tend to use the other-way-up equation, although you seem to favor the above ...

... AI otherwise

Exposure value - Wikipedia

en.wikipedia.org

Ted Cousins · Wednesday at 6:05 PM

As to Ev, Wikipedia says

Wiki said:
The ratio t/N2 could be used to represent equivalent combinations of exposure time and f-number in a single value. But for many such combinations used in general photography, the ratio gives a fractional value with a large denominator; this is notationally inconvenient as well as difficult to remember. Inverting this ratio and taking the base-2 logarithm allows defining a quantity Ev such that EV=log_2(N^2/t), pardon the ASCII ;-)

I'm sure you've read that before!

best,

Ted.

Doug Kerr · Wednesday at 6:09 PM

Hi, Ted,

Ted Cousins said:
As to Ev, Wikipedia says

<snip>

I'm sure you've read that before!

Indeed.

Thanks.

Best regards,

Doug

Doug Kerr · Wednesday at 7:23 PM

Hi, Ted,

By the way, I think that passage from Wikipedia on Ev is very nice.

Best regards,

Doug

Ted Cousins · Wednesday at 7:38 PM

Doug Kerr said:
Hi, Ted,

By the way, I think that passage from Wikipedia on Ev is very nice.

Best regards,

Doug

Agreed!

Equations in my OPF posts

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