What I (and You) Don't Know—Part 1

By Ctein

My column this time carries a request to you, my faithful readers, for enlightenment and edification (translation: I need to learn stuff. You guys know stuff. Gimme gimme gimme.)

But first, this important announcement (translation: blatant commercial plug follows):

Laurie Toby Edison has a special holiday deal on her two books, Women En Large: Images of Fat Nudes and Familiar Men: A Book of Nudes.

(Workplace warning: As should be obvious, there are nudes at the links.)

You can order them via the PayPal buttons here for $15, including shipping, instead of the usual $25.

Not really stocking-stuffers (unless you roll them up, which would be a horrible thing to do a book) but they sure are priced that way. At $25, they're more than worth the money. At $15, you should all buy these books!

(Disclaimer—Laurie's my best friend, sometimes photographer partner, and I provided financial support for the first book and the title for the second. Just so you know I'm totally objective in my praise of these books [smile].)

We now return to the program in progress
In a recent conversation with Ben Syverson, it became apparent that I may (and I emphasize the word may) have been steering folks wrong for years. When I read digital camera resolutions given as lines horizontal by lines by lines diagonal, I have understood that to mean total lines of resolution across the entire field of view. Ben has recently noted that on dpreview, they give lines of resolution per unit vertical dimension. In other words, if you have a 2:3 format sensor, it sounds like you would need to multiply the horizontal resolution line number by 1.5 to get the total resolution horizontally across the sensor.

At least, that's how he reads it, and I read it the same way.

Problem is I go back and look at old Pop Photo reviews, before they started giving a single resolution number, and they don't say anything about resolution in lines per unit length. The way the text reads, it sounds like they're talking about lines across the entire field of view.

The numbers aren't compatible. The ratios of horizontal to vertical (or diagonal) resolutions in the Pop reviews aren't particularly different than the ratios in dpreview reviews. I doubt that the sensor or software characteristics have changed that radically. So one of these interpretations has to be wrong. I don't know which one!

If I could find an original Pop Photo article which described their testing procedures, it might illuminate this. I've tracked back to May, 1999 so far, and haven't been able to locate it. (I don't actually know that they wrote such an article, but it would've been their habit to do so.)

Does anyone have informed knowledge on this subject or can point me to references that might clear this up? I would really, really like to know if I've been getting it wrong all these years.

Understand, I'm not looking for "seems to me"'s or "in my humble opinion"'s. I've got plenty of those. I need hard (or at least semi-solid) information.

Thanks for your help!

____________________

Ctein

Featured Comment by David A. Goldfarb: "Hey! That fellow wielding the cane on Laurie Toby Edison's blog is indeed a familiar man. For fans of science fiction, I recommend his early novel, Babel-17. If you're interested in New York gay culture or what it was like to be part of the scene in the East Village in the 1960s, take a look at his memoir, The Motion of Light in Water. It explains, indirectly, a lot of what is happening in Babel-17. He's also written a few intellectually and politically challenging and sexually transgressive novels called Hogg and The Mad Man. He was also the subject of a documentary film recently called 'The Polymath.' His name is Samuel R. Delany."

Comments

[David]

This may or may not help. Talk to your local neighborhood Reference Librarian and ask him (gender non-specific) whether they can provide you with information regarding which index indexes articles by Pop Photo. I'm sure one, if not more, exists. Once you know that, you can probably find a local University Library that carries the index and you can then search to find the information you want.

If this proves difficult to implement for me, contact me and I will talk to an arts librarian here at the U. to get the information.

Regards, David

[Eduard de Kam]

Ctein,

When the first ISO testcharts for digital camera's came out, the numbers one was supposed to be looking for was lines per image heigth. So square images get an unfair advantage, ther's is nothing you can do about it.

I at this time present my results as a percentage of the Nyquest frequency when I test lenses, so I sort of jump over the actual number of pixels.

[Adam Isler]

Did you look at this glossary entry on resolution at DPReview:
http://www.dpreview.com/learn/?/Glossary/Digital_Imaging/Resolution_01.htm ?

Adam

[Hugh Crawford]

The readers guide to periodical literature, the google of the dead tree era. The online version is here
http://tinyurl.com/54rcmh

WilsonWeb Journal Directory has an index of pop photo from 1982 to now , that should cover what you want.

BTW , if you have 100 alternating black and white stripes, how many lines do you have?

101 ?
100 ?
99 ?
49 ?

[Ctein]

Dear Adam,

Yup, like I said, that's how we're reading it. Problem is not with understanding dpreview's methodology, it's with understanding Pop's old methodology.

Dear Hugh,

WWJD looks wonderful, but it won't let me access it without a subscription or institutional affiliation.

"Lines" comes from television metrology. Photography measured resolution in line pairs, TV did it in scan lines (or equivalent). So 100 black and white lines is 100 lines or 50 line pairs.

pax / Ctein

[Howard Cornelsen]

Hugh--
Regarding counting black and white stripes:

In classic optics, line pairs per millimeter is identical to lines per millimeter. That's because it takes two black lines to define one white line.

Therefore (I think) in your example, you have 50 line pairs or 50 lines.

[KGB]

I got into photography because I was bad at math...

I read your post carefully.

I got into photography because I was bad at math...

[Laurie Toby Edison]

Ctein,

Many thanks for talking about the holiday book sale, and many thanks to the people who have been ordering the books.

Just wanted you to know that there was a glitch in PayPal, and even though the $15 includes free US shipping, some people were charged the additional $5 by PayPal. We've refunded these folks $5 and the glitch is fixed. International shipping is at a reduced rate of $7, which will be added to the $15 by PayPal.

We didn't expect so many international orders and we really appreciate them. We love it when the books travel. Hope the people who receive the books for the holiday are really happy with them.

Best,

Laurie

[Richard]

Sounds like you should have stuck to film, like Stalin. -- Rich