Apature

[Razr]

(SNIP)
Oh yeah ... just how do I stop up (STOP UP?) to Aperture f/2.8 ... on a f/4-5.6 lens?

Why did you post such a nonsensical question? To amuse yourself or others?

In Manual or Av? I figure I can save a lot of money on high-priced glass if we can figure that one out.

More nonsense.

[Prospero]

Razr, that's not at all what they mean by "forcing a camera to use the optimum apertures".

The optimum aperture is the aperture where the lens performs best. This is generally between f/5.6 and f/11. It is a couple of stops away from the maximum aperture at a certain focal length.
Yes, with aperture priority, you can force a camera to use that aperture. It is easily within the range of apperture values available.
However, you can still not force the camera to use an apperture that is not available...

[JTL]

Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.

Amusing as this thread is, it all goes back to the above statement. It is simply not true. Nothing can make it true. All the word games and symantic gymnastics in the world created to defend the statement are meanilngess. I suggest that all efforts be redirected at this statement and this statement alone and that any other statements made in defense of it be ignored as they are just distractions.

If it weren't the funniest (yet most pathetic) thing in all of mediadom...I don't think this thread would have lasted this long.

[Razr]

(SNIP) Razr, you obviously don't have a clue.
The Wikipedia article you link to does not support your case. It says that in apperture priority mode you select the apperture and the camera calculates the shutterspeed. That's all. There's really nothing in that article about locking appertures into place.

The mote in your eye let you miss this part of the Wikipedia article which says:

"In addition, aperture priority mode allows the photographer to force the camera to operate the lens at its optimum apertures.

How did you miss that in the Wikipedia article? Of course "force the camera" to operate the lens at its optimum aperture" simply means any aperture of the photographer's choce (of all the apertures on any given lens).
How did you miss that crucial (and 100% germane) sentance?

The only thing which is locked when using the aperture priority mode are the apperture blades

Oh thank you-thank you. I finally get someone to see the light so to speak.

...if and only if you select the maximum aperture.

not true. Av mode can be set on any available aperture.

(SNIP) I guess in the next thread you will start claiming that if you twist the zoom ring of a lens far enough, you can push a 70-300 up to 400mm

Only a total photgraphic neophyte could even think of duch an absurd posit.

[Razr]

Amusing as this thread is, it all goes back to the above statement. It is simply not true. Nothing can make it true.

This Wikipedia article (below) makes it "true":

From Wikipedia:
"In addition, aperture priority mode allows the photographer to force the camera to operate the lens at its optimum apertures.

"Optimum apertures" being the ultimate choice of the photographer.

All the word games and symantic gymnastics in the world created to defend the statement are meanilngess.

I'm sure you'll write Wikipedia about their "symantic gymnastics".

If it weren't the funniest (yet pathetic) thing in all of mediadom...I don't think this thread would have lasted this long.

From Wikipedia:
"In addition, aperture priority mode allows the photographer to force the camera to operate the lens at its optimum apertures.

Don't foget to tell them what they (don't) know about aperture priority, them daring to publish such nonsense!

[JTL]

The mote in your eye let you miss this part of the Wikipedia article which says: How did you miss that in the Wikipedia article? Of course "force the camera" to operate the lens at its optimum aperture" simply means any aperture of the photographer's choce (of all the apertures on any given lens).
How did you miss that crucial (and 100% germane) sentance? Oh thank you-thank you. I finally get someone to see the light so to speak. not true. Av mode can be set on any available aperture. Only a total photgraphic neophyte could even think of duch an absurd posit.

Now Wikipedia trumps physical reality!

Because the writer of the Wikipedia statement was sloppy (or ignorant or stupid) and left out the part that says: "force the camera, within the limits of max aperture for a given focal length" we have to listen to these endless WRONG rants...AMAZING BUT TRUE!

Too bad the World Weekly News is out of business. We could have gotten some quotes from them as well. There's always the Enquirer, I guess...

[Prospero]

The mote in your eye let you miss this part of the Wikipedia article which says: How did you miss that in the Wikipedia article? Of course "force the camera" to operate the lens at its optimum aperture" simply means any aperture of the photographer's choce (of all the apertures on any given lens).
How did you miss that crucial (and 100% germane) sentance?

No, if you actually read the wikipedia article one sentence further you will read:

Commonly, lenses provide greatest resolving power with a relatively medium-sized aperture.

Hence, the medium sized aperture - which would be somewhere between f/5.6-f/11 - is the optimum aperture which is refered to in the sentence before.

not true. Av mode can be set on any available aperture.

Yes, if you quote out of context, you can make everything seem untrue. What I said was that only at the maximum apperture and minimum for that matter, the apperture blades will stay in the same position if you zoom in. For the other focal lengths, the blades will change when zooming to make sure the f-stop stays constant.

Only a total photgraphic neophyte could even think of duch an absurd posit.

Of course that is a absurd posit. But it is just as absurd as opening up the diaphragm of a lens more than its maximum.
So who is the neophyte here...

[Ray Schnoor]

Now we are getting somewhere

So... You mean like for the 17-70 sigma... its F/2.8-4.5 which means at 17ish its maxed at 2.8 and 70 its maxed at 4.5? so it cant go below 4.5 at 70 but like the 70-200 F/4 COULD go to f/4 at 70 AND 200? so its just the max? and its not fixed and can be shrunk? thanks BTW those were fast replies!

Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.

not true. Av mode can be set on any available aperture.

Since f/2.8 is not available at the long end of said Sigma 17-70 f/2.8-4.5 lens, you obviously cannot set it at f/2.8 in Av mode at the long end of the zoom range.

Finally, a statement from Razr I can agree with. Thank you.

Ray.

[Razr]

Razr, that's not at all what they mean by "forcing a camera to use the optimum apertures".
The optimum aperture is the aperture where the lens performs best.

I got no problem with that, except they said "optimum apertures", (plural).

This is generally between f/5.6 and f/11.

Generally quoted as being "the sweet spot" or "two stops down from the maximum aperture".

(SNIP) Yes, with aperture priority, you can force a camera to use that aperture.

My precise point all along.

However, you can still not force the camera to use an apperture that is not available...

I never said so nor have I ever suggested you could (use an unavailable aperture-duh.)

[Ray Schnoor]

This Wikipedia article makes it "true

"In addition, aperture priority mode allows the photographer to force the camera to operate the lens at its optimum apertures within the limits of maximum/minimum aperture for a given focal length of the lens."

OK! There we go.

Ray.