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09-29-2010, 02:39 AM - 1 Like   #1
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Stopping down

Hello,

i know its a very silly question, but.... what do we mean by "stopping down" in photography?


Thanks

09-29-2010, 02:46 AM   #2
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Stopping down a lens simply means to close down the aperture. Say, move the aperture from f2.8 to f4.

BTW, there are no silly question.
09-29-2010, 02:46 AM   #3
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Making a smaller aperture, i.e. larger f-number.
09-29-2010, 02:48 AM   #4
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ok thanks...

Because i was reading comments, and they were saying continuously "stop down" and i wasn't understanding what they meant!

So in general by stopping down, usually gives sharper images? At least that's what i understood from some other comments

09-29-2010, 02:50 AM   #5
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When you use your typical automatic lens, you're always metering and focusing while the lens is at its widest aperture, which means the viewfinder is at its brightest. It only engages to your actual aperture when you hit the shutter.

However, with modern and older manual lenses, you can stop down to the aperture you want to use while composing and focusing--even before hitting the shutter. This darkens the viewfinder if you're at like F11, for example, and actually shows you your depth-of-field effect in the viewfinder.

Depending on your habits, photographers stop down mainly to preview the depth of field.
09-29-2010, 02:54 AM   #6
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QuoteOriginally posted by fekish Quote
ok thanks...

Because i was reading comments, and they were saying continuously "stop down" and i wasn't understanding what they meant!

So in general by stopping down, usually gives sharper images? At least that's what i understood from some other comments
A smaller aperture--larger number--gives you greater depth of field:

The distance in front of and behind your main subject that you're focusing on.

The flat surface of a wooden block that's in focus at F16 is not sharper than at F2.8, but at F16, more of the REAR of the block will be in focus at F16 than F2.8.
09-29-2010, 02:55 AM   #7
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Hello Fekish. I had the same question and found in google that "stopping down" means closing the aperture to higher number (for example, going from f/4.0 to f/5.6 is stopping down). When you do this, less light gets to the film (or sensor) and shutter plane and your depth of field (or the amount of the "picture" that is in focus) is increased. that's what happens while stopping down:

f/2.8


f/22



as you can see, picture taken with stopped down lens is sharper (because tree branches in the background are now also focused).
09-29-2010, 02:59 AM   #8
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ok thanks! That's great help from everyone!

Yes i understand the meaning of aperture, its just many people were saying stop down to get sharper images on some less expensive lenses , and i was wondering about that...

09-29-2010, 03:06 AM   #9
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QuoteOriginally posted by fekish Quote
ok thanks! That's great help from everyone!

Yes i understand the meaning of aperture, its just many people were saying stop down to get sharper images on some less expensive lenses , and i was wondering about that...
That's right, but bear in mind that when you stop down, you get less light on the sensor, so you'll need longer exposure, which may require shake reduction or tripod
09-29-2010, 09:28 AM   #10
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QuoteOriginally posted by fekish Quote
ok thanks! That's great help from everyone!

Yes i understand the meaning of aperture, its just many people were saying stop down to get sharper images on some less expensive lenses , and i was wondering about that...
At some point, stopping down too far will cause the dreaded diffraction loss of image quality. I've never notice it, though, but I don't normally shoot at f22.
09-29-2010, 12:39 PM   #11
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QuoteOriginally posted by fekish Quote
its just many people were saying stop down to get sharper images on some less expensive lenses , and i was wondering about that...
People advise stopping down with many less expensive lenses because often they produce better images with smaller apertures (higher resolution, less abberations, better contrast, less softness). When stopping down is talked about in that way it is refering to properties of that lens, not to the depth of field effect.

In contrast to that some lenses are quite good at larger apertures and do not "need" to be stopped down for image quality reasons.
09-30-2010, 05:05 AM   #12
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thats why many lenses when tested come at best or start to be best at F8 rather than the wide [numericaly smaller] settings like F4.5 . Typically this applies more to zoom lenses and is not so true with a fixed size lens.
adwb
09-30-2010, 07:18 AM   #13
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QuoteOriginally posted by OrenMc Quote
BTW, there are no silly question.
Thanks for that!!! A no flame, straight-up response in the highest tradition of a Pentax enthusiast!!!
10-01-2010, 08:52 PM   #14
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Stopping Down and Sharpness

Another thing to keep in mind with stopping down (closing down) the aperture. The rule of thumb for lenses is that a lens is sharpest 2 to 3 stops closed from its widest opening. For a lens with a maximum aperture of f1.4, it would be sharpest at f2.8 or f4. For a lens with a maximum aperture of f4, it would be sharpest at f8 or f11. Do you see the difference here? A lens that has a maximum aperture of f1.4 is going to let in 3 stops (8 times) more light than a lens with a maximum aperture of f4, at its sharpest setting.

Additionally, as was stated, as you continue to stop down to the smaller apertures, diffraction occurs, or the scattering of the light through the aperture, forming a wave pattern that reduces sharpness and image definition (it gets real technical but see Diffraction - Wikipedia, the free encyclopedia ). So with an f1.4 lens, you have the best sharpness at say f4 and don't start getting into problems with diffraction until about f16, or about 5 stops with good sharpness and image definition. With the f4 lens you only get about 2 stops. Quite a big difference when you think of it.

Now you know why those fast lenses are so desirable!
10-04-2010, 12:52 PM   #15
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QuoteOriginally posted by BigDave Quote
Now you know why those fast lenses are so desirable!
Indeed. I'm still trying to get my paws onto some 50-55-58/1.2 (holy grail). But some slower lenses start off sharp, and stay there. I'm thinking especially of my Super-Takumar 35/3.5, Meyer Helioplan 40/4.5, Macro-Takumar 50/4, Jupiter-11 135/4, Meyer Telemegor 180/5.5, and Tele-Takumar 200/5.6. These are not cheap soft lenses wide-open.

There are trade-offs in lens designs. Fast lenses: more glass, more correction, more weight, more money... and more elements means slightly flattened images. Simpler, slower lenses with fewer elements: lighter, cheaper, smaller... and often greater dimensionality. Some tessars and triplets are prized for their 3D Leica-oid images.
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