Very informative. I always stumble when people talk about F Stops and what they used but this is a wonderful demonstration

Hmmm,
I teach photography,
Maybe I should start teaching shit about computers with my own over simplified explanations based on pseudo-correct information.

James, if you disagree with Geoff and think he should have / could have done better, well then post a better explanation yourself. We'd appreciate your sharing your knowledge, not just your criticisms.

Jim

Shouldn't the writer have said, "LARGE apertures are often used for portrait work, leaving the subject sharp and the background pleasingly blurry," rather than SMALL apertures?

A SMALL aperture (11 or 16 )is a SMALLER lens opening thus allowing in less light and providing a deeper depth-of-field.

James, please post where you teach. I want to be sure and avoid your class. I want teachers who instruct, not bitch. Geoff is giving simple information for users who would normally always use the auto setting.

Simplified information is different than incorrect information. Simple instruction leads some users who are overwhelmed by complicated jargon into learning more, and maybe, eventually learning all of the jargon and more complicated information.

If those of us in the computer field had the same attitude that you display, only a very few computer programmers would have access to computers.

The f/number can be confusing and seems nonsensical until you figure out what it really means. The term "f" is the focal length of the lens. So the aperature size is expressed as a ratio of the focal length. An f/4 aperature on a 105mm lense gives an opening through the lens of about 21mm. If I remember the math--and I don't always--the area of the opening roughly doubles with every full f-stop decrease, so you'll get twice as much light at f/11 as you would when the lens is at f/16.

Good grief.

Usually I let this stuff roll off my back, but I won't this time.

Part of the confusion over aperture is the smallest aperture occurs at the highest numbered setting. Since our target for this series (people shooting in "AUTO") see the number, not the actual opening, I referred to it.

Paul, in that light, please read the sentences that precede your objection: "The higher the f-stop the larger the area of your shot that's in focus. If you need a large area in focus choose a higher f-stop number. For shallower depth-of-field (that's what it's called) choose a lower f-stop. Small apertures are often used for portrait work, leaving the subject sharp and the background pleasingly blurry."

I am trying to reach an audience that is frustrated because the camera they bought to solve their problems has become an expensive point-and-shoot. I am trying to show them the camera won't bite them. It's possible they're gun shy because they've already spoken to James or you.

Geoff Fox

Bob-

F-stop refers to focal ratio. You're correct. The variables are focal length and diameter of the opening.

Geoff

Oh yeah, one more thing...James, get a grip: remember, those who can, do; those who can't, teach.

One thing you might have pointed out is why the f-stop numbers form such a weird progression at first glance: the numbers relate to the *diameter* of the iris, while the amount of light allowed in is determined by the *area* of the iris.

Think back to your junior school maths classes, and you'll remember that area varies as the square of the radius (or diameter), so in order to double the area of the iris (and thus double the amount of light), you multiple the diameter by the square root of 2, i.e. 1.4.

Since that would result in some even more odd numbers, the decision was made years ago to round off to a couple of significant digits, resulting in the sequence we see today: 1.4, 2, 2,8, 4, 5.6, 8, 11, 16. Squaring each to give the area, you'll see that each step is roughly double the last: 2, 4, 7.84, 16, 31.36, 64, 121, 256.

The whole article was shot through with misleading simplifications and/or downright errors. For example, greater depth of field does not increase the "area" of your picture that is sharp. And to say that "Small apertures are often used for portrait work, leaving the subject sharp and the background pleasingly blurry" simply perpetuates the confusion that the author is trying to clear up. It's smaller f-stops, not smaller apertures, that reduce depth of field and make the background blurry.

If I were taking a photography course from James and he described the theory and effects of aperture this way, I'd walk out, drop the course and demand a refund.

Having said that, I agree that for the purposes of this column, a few simplifications were in order.

Having said that, whining about the perfectly logical and eminently useful system devised by photographers - f-stops and their relationship to exposure and the standard shutter speed scale - was uncalled for. Skip the editorializing and just get on with your version of an explanation. And do try to avoid statements that are flat out wrong.

Geof, this article was fine for the intended audience. The one error pointed out before was just your statement "Small apertures are often used for portrait work, leaving the subject sharp and the background pleasingly blurry." It was clear to me that you meant "small f-stop settings..." and if you can fix it, that would be good.

I bought my first (and only) SLR back in 1984 when my first child was born. I was totally new to the control this provided over the point-and-shoot cameras I had when I was younger. The main reason I quickly gravitated to Aperture priority settings on that old SLR (no automatic mode) was that I then had to just ensure the timing was at least 1/10 sec and not faster than the camera could handle. Since the shutter timing was visible within the viewfinder that worked very well. Now with a DSLR I still tend to go with Aperture Priority for similar reasons.

I learned something new today about the f-stops increasing by a factor of 1.4 each step. I guess I should think of that as reducing the diameter of the Aperture by a factor of 1.4 each step up in f-stop. It makes me wonder if the DSLRs in Shutter Priority mode have a finer granularity for the f-stop setting. Perhaps not, since the timing adjustment is also not so granular. Hmm, I think I understand this just a bit more than I did before.

Posting the example photos should make it clear to beginners. Good. And make them more interested in getting out and trying it out themselves. Better. Our 1, 2, 3 brains Do have a heard time grasping the "larger integer is smaller hole" thing. We've also the identical problem with pipe, wire and shotgun "Gauges", with the smaller numbers being larger in hand.

The one other way we could possibly make it easier for complete newbies- and with decent DSLR's cheaper than decent Film Auto Focus SLR's 10 years ago they are legion- would be to number them appropriately. The "First Hole" (largest) labeled 10 (or 12~), with the "Smallest Hole", naturally, a 1. And, for those needing a mathematical explanation, include a link in the owner's manual or simply tell those to "look it up".

For me, there never was a better teacher than my first new SLR, Minolta SRt-101, and its TTL (through the lens) management with its accompanying pointer and hoop in the viewfinder.

I try to avoid any lengthy explanation of the whys of aperture for obvious reasons.

AND FOR ANYONE USING THE OFFENSIVE PHRASE
"those that can't, t...., ala Paul above, probably can't do either well. Amen.

As a novice with an SLR I found the author's explaination quite informative. Now I get it for 5 minutes instead of a nano second.