Apature

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Originally Posted by Zeva

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!

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Originally Posted by Razr

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.

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Originally Posted by zmikers

Maybe I misread your post here but I think you are wrong. If you are in Av or M mode with a f/2.8-f4.5 lens on your camera and your Aperture is set at f/2.8, as you zoom the aperture will not stay at f/2.8, it cannot. It will change to match the max aperture to that specific focal length. So the sigma 17-70 f/2.8-4.5 has a max aperture of f/2.8 only at 17mm and a max aperture of f/4.5 at 70mm.

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Zmikers is correct here. If you have a f/2.8-4.5 lens, you cannot change it to a f/2.8 lens just by putting it in Av or M mode. The max aperture changes throughout the focal range and the aperture value will change accordingly in both Av and M modes.

Ray.

Just so we're clear ... the numbers posted on the lens are the MAXIMUM (widest) aperture the lens can acheive. If the aperture is a sliding range, such as f/4-5.6 ... the MAXIMUM aperture of the lenses closes down as you ZOOM to a longer focal length.

If you set the camera to 70mm and f/4 aperture ... then zoom towards 300mm, the aperture begins to incrementally close down along the way ... to f/4.5 - f/5 - f/5.6 (somewhere around 235mm)

Doing this on a 18-200mm f/3.5-f/6.3 or an 18-70mm f/3.5-5.6 lens ... the effect is even more pronounced.

As the graph depicts:
Attachment 30168

At the 40mm focal length, you can see that there is a heck of difference in max aperture between these two lenses, the 18-200 being the "brighter" of the two and therefore, a bit better for indoor use.

I hope this kind of helps. If not ... it's "book time" ... and get the camera out ... for a live demo. :D

Using any make/model of "Variable aperture" lens, set lens/camera body to the "A" (Av) function;
OR: put the camera body on full manual, which "disables" (disconnects both shutter and aperture automation from the camera body).

With either setting, the only way the aperture CAN BE CHANGED is manually: end of lesson.

C'mon guys, surely you know "full manual" operation means what it says? That NOTHING happens to the aperture or shutter unless the photographer makes it happen?

In "Av" mode, aperture automation is disabled thus (by definition) means "fixed aperture" .

Why argue with me when the Full manual and Av operational protocols define what will happen (or not)?

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Originally Posted by Razr

Using any make/model of "Variable aperture" lens, set lens/camera body to the "A" (Av) function;
OR: put the camera body on full manual, which "disables" (disconnects both shutter and aperture automation from the camera body).

With either setting, the only way the aperture CAN BE CHANGED is manually: end of lesson.

C'mon guys, surely you know "full manual" operation means what it says? That NOTHING happens to the aperture or shutter unless the photographer makes it happen?

In "Av" mode, aperture automation is disabled thus (by definition) means "fixed aperture" .

Why argue with me when the Full manual and Av operational protocols define what will happen (or not)?

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Are you serious????

Take any zoom with a variable range and try to get the widest aperture at the longest zoom. It ain't gonna happen, that's why it's variable along the zoom range. The only variable zoom I have is Canon's efs 10-22 f3.5-f4.5. There is no way in any mode, av, manual, or whatever, that I'm gonna get f3.5 @ 22mm. It won't/can't happen. Let's take your thinking to primes - all I have to do is set mode to manual, choose f1.4 and my f2.8 suddenly gains that aperture? BS!

I think you are playing with words. I guess you could say that yes, the aperture is fixed along the variable zoom range :D:D. , but you still ain't gonna get the widest aperture at the longest zoom.

Just you try setting your camera to manual, with a variable aperture zoom lens set at max aperture, at shortest focal distance, then zoom and see if your aperture stays at f/2.8. No such luck!

I'm... kinda surprised you don't already know this. But then... do you actually own a DSLR?

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Originally Posted by Razr

Using any make/model of "Variable aperture" lens, set lens/camera body to the "A" (Av) function;
OR: put the camera body on full manual, which "disables" (disconnects both shutter and aperture automation from the camera body).

With either setting, the only way the aperture CAN BE CHANGED is manually: end of lesson.

C'mon guys, surely you know "full manual" operation means what it says? That NOTHING happens to the aperture or shutter unless the photographer makes it happen?

In "Av" mode, aperture automation is disabled thus (by definition) means "fixed aperture" .

Why argue with me when the Full manual and Av operational protocols define what will happen (or not)?

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This quote from above just says it all: "C'mon guys, surely you know "full manual" operation means what it says? That NOTHING happens to the aperture or shutter unless the photographer makes it happen?"

The photographer makes it happen when he zooms the lens, thus changing the maximum aperture of a "variable maximum aperture" lens such as the Sigma 17-70 f/2.8-4.5 lens used as an example previously. Maximum aperture at 17mm = f/2.8, mamimum aperture at 70mm = f/4.5.

C'mon Razr, surely you know you can't make a lens aperture larger than its maximum value.

from Razr's quote: "Why argue with me when the Full manual and Av operational protocols define what will happen (or not)?"

Because changing a setting on a camera cannot change the makeup/physics of the lens. If it did, no one would ever buy those expensive 70-200 f/2.8 lenses. There would be no need.

Ray.

ROTFLMAO....

This is great! Pee-in-the pants funny! Way more entertaining than any current TV show or movie. More please!!! :D:D:D

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Originally Posted by Razr, in the HDR thread

**The “pros”, me among them, generally use filters in that the proper filters do what filters are designed to do: modify incoming light in order to help balance exposures.
Better taking 20 seconds to spin on an ND or Polarizer filter than spending minutes per image post processing keepers.
Even better, our workflow is minimized whenever we use filters.

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So, Razr, you count yourself among the pros, yet you don't understand the concept of a variable aperture lens ??? :eek:

I can understand where your confusion comes from. Take for instance the Sigma 70-300 f/4-5.6. If you were to use it with the aperture ring, you can set the ring at f/4 even when it is zoomed in to 300mm. However, the lens is then not really f/4 but f/5.6. The reason that the aperture ring does not show this is that the aperture ring is too small to fit the values for every range of focal lengths. Similarly, at 300mm you can stop down up to f/36 while the ring shows f/22.

If you were a newbie, your confusion would be understandable. But really, if you are a "pro" you should know better.... :rolleyes:

lol funny stuff. obviously the 4/3rd's system, LEICA and OLYMPUS have devised a way to counteract this issue. us canon and nikon fans have to just suck eggs. lmao

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Originally Posted by fionndruinne

Just you try setting your camera to manual, with a variable aperture zoom lens set at max aperture, at shortest focal distance, then zoom and see if your aperture stays at f/2.8. No such luck!

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That is only true if the aperture is still linked to the camera by electrical or physical connection.

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I'm... kinda surprised you don't already know this. But then... do you actually own a DSLR?

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Yep: two of them: OLYMPUS E-500 & OLYMPUS E-510 and as soon as it ships, an OLYMPUS E-3.
All you guys have to do is tell me how, after you unlink (disable) the mechanical/electrical connection to the aperture, how then can an aperture "move" (closes down)?
*Remember, nearly all mechanical lenses are actuated by levers-etc.
Nearly every electrically actuated (CANON EOS for example) lens depends solely on the camera body connections for directions as to what shutter speed or aperture setting to use.
Break (disable) that/any connection to the aperture by setting "Av" or "M" on the body, you have TOTALLY IMMOBILZED the aperture.
When you are shooting in full manual for example, whatever aperture you set on the camera (the lens for manual lens) that is the only aperture you can use.
Take a PENTAX "M" or "K" mount lens for example: mount it on a PENTAX D10. Everything works between the two except autofocus. Why? No autofocus motor and/or electrical connections Disable the aperture by moving the lens off the “A” setting and now the aperture too is disabled.
The only way that aperture can then move is by hand (or dial with lenses with no aperture ring).
The same thing occurs when you break off the aperture tang on a PENTAX "KA2" lens. With no connection to the body, that lens remains wide open.
Take a CANON EOS body, mount an EOS lens then disable the electrical connection controlling the aperture (which is what the body does in Av mode) by setting the dial on "A".
Regardless of the focal length set on that disabled EOS lens, the aperture will not move (close down).

Let's try this: you have a train: you unlink the Caboose and then drive off: can (does) the Caboose ever move on its own? You have a chain: you cut the chain and drag the section left in your hand with you. Does the uncut chain move?
In other words, an aperture must have some sort of connection-electrical or mechanical, to the camera body before it can be actuated.

I think what all of you have failed to notice is any lens in Av mode on a battery driven body and/or in full manual setting on any type of body, the aperture is disabled and has no way to move on its own.

Here’s what mystifies me: in nearly every instance, everyone here knows when you mount a lens adapter to a camera body then mount any kind of zoom lens on the adapter, you have to use (by default) a fully open aperture, manually stopping down your shutter and aperture to obtain the correct exposure. Why? No connections to the camera body.

The same goes when you set a lens on the “Av” (aperture priority) setting: there is no connection (mechanical or elctrical) to the camera body.