What does “stopped down” mean?

[Displaymyname]

with regards to lenses, what does the term “stopped down” mean? Apologies if this question isn’t clear.

 

[tedolf]

with regards to lenses, what does the term “stopped down” mean? Apologies if this question isn’t clear.

Shooting at the selected aperture when it is less than the maximum aperture of the lens.

tEdolph

 

[Displaymyname]

I should have expanded on the question. What is a specific instance where you might need to stop down? When does stopping down come into consideration? Thank you.

 

[FrancoD]

Some adapted lenses don't have an auto diaphragm, one that the adaptor can stop down to the chosen aperture by itself, so you need to do it yourself.

 

[TacticDesigns]

I should have expanded on the question. What is a specific instance where you might need to stop down? When does stopping down come into consideration? Thank you.

My old Pentax dSLR actually does this when I use old Pentax-M manual focus lenses.

So lenses that have an aperture lever, but it is not an automatic aperture.

When I compose the picture, I get a bright viewfinder because the camera lets the lens open up to its max setting.

Then if I press the AE-L button, it closes down the aperture to take a meter reading at the aperture setting I've selected and then sets the shutter speed at that point.

I release the AE-L button and the camera opens up the aperture again for composing.

When I actually press the shutter button, the lens gets stopped down again for the actual exposure.

There are other reasons for stopping down the lens.

I guess like when you use the preview button, the lens is stopped down and you can preview the depth-of-field.

Or . . . if using an old lens adapted to another camera (like mirrorless) you may need to manually stop down the lens, because the camera may not have a way to stop down the lens itself.

Take care & Happy Shooting!


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[Michael Fryd]

with regards to lenses, what does the term “stopped down” mean? Apologies if this question isn’t clear.

"Stopping down" generally refers to reducing the size of the lens's aperture.

A 100mm f/2.8 lens has a maximum aperture of f/2.8. However, frequently we will shoot with a smaller aperture diameter.

We might say we are "stopping down" when we select a smaller aperture diameter (such as f/5.6).

Many cameras leave the aperture all the way open until we are actually taking the photo. At that point the lens "stops down" to the smaller aperture to take the photo, and then opens back up.

Many cameras allow us to stop down the lens without taking a photo. This is generally called "depth of field preview".

Background

The typical modern camera lens has a variable aperture. This is essentially a hole with an adjustable diameter. This allows the photographer to select what size hole to use. Larger apertures allow more light into the camera. This tends to reduce image noise, and allow shorter shutter speeds. However, the larger hole also results in shallower depth of field.

The shape of the aperture approximates a circle. The "f/stop" of a lens is the ratio of the focal length of the lens to the aperture's diameter. "F/4" is actually a mathematical equation that represents the focal length of the lens divided by 4.

F/2 is an aperture diameter half the focal length. F/4 is 1/4 the focal length. On a 100mm lens f/2 is a 50mm aperture diameter, and f/4 is a 25mm diameter.

Thus the largest aperture is the "smallest" number. In this context 4 is larger than 8.

When we say that a lens is an f/2.8 lens, we are saying that f/2.8 is the widest aperture available. Normally the lens stays at the widest setting until you take the photo. This lets in the most light for the DSLR viewfinder, and yields less noise on a mirrorless viewfinder.

As depth of field is shallower at the widest aperture, it makes sense for the camera to focus at the widest aperture, and then stop down for the photo. (there are disadvantages here as some lenses shift focus when they stop down).

 

[BobSC]

with regards to lenses, what does the term “stopped down” mean? Apologies if this question isn’t clear.

In a typical situation on this forum, it probably means that the lens aperture was closed down considerably. Either a poster might be suggesting that the lens should be stopped down in order to increase the depth of field, or maybe they were commenting that because the lens was stopped down too much the background was distracting (on account of too much depth of field).

People might also suggest that you should stop down the lens to get a longer shutter speed (if you want car lights or running water to be streaks).

Today I was taking flash photos in our house to document some construction. With flash, the fastest shutter speed I can use is 1/250. With the flash at minimum power, the photos were washed out, so I had to stop down the lens (close the aperture) to get a good exposure.

Frequently lenses are their sharpest when they are stopped down two stops from wide open. So if it's an f/4 lens, then maybe f/8 is the sharpest.

All lenses suffer from dispersion (loss of sharpness) when they are stopped down too far. So any lens might be less sharp at f/22 than it is at f/16.

 

[BobSC]

Today I was taking flash photos in our house to document some construction. With flash, the fastest shutter speed I can use is 1/250. With the flash at minimum power, the photos were washed out, so I had to stop down the lens (close the aperture) to get a good exposure.

Silly me. I should have known to check the ISO. It was set to 6400. LOL.

 

[Displaymyname]

Thanks. Very good explanation

 

[Michael Fryd]

I should have expanded on the question. What is a specific instance where you might need to stop down? When does stopping down come into consideration? Thank you.

Reasons you may want to "stop down":

• You want more depth of field. With some lenses if you shoot wide open you may have the tip of the model's nose in focus, but not her eyes. If she's not directly facing the camera, you may need to stop down if you want both eyes in focus.
• You want to use a longer shutter speed to blur motion. For instance you want some motion blur in a passing car.
• You may want a longer shutter speed so you are below the camera's max sync speed, so you can easily use fill flash outdoors.
• Not all lenses are sharpest when fully open. many are sharpest about two or three stops down from wide open.

 

[baloo_buc]

All lenses suffer from dispersion (loss of sharpness) when they are stopped down too far. So any lens might be less sharp at f/22 than it is at f/16.

It's diffraction. Dispersion is another phenomenon. You get chromatic aberration from it. And the rainbow on the sky or near a waterfall.

 

[baloo_buc]

It means that the lens is at a smaller aperture as the maximum aperture. E.g. if your lens has f/3.5-f/5.6 maximum aperture f/5.6 is stopped down at wide end while f/5.6 is not stopped down at tele end.

The term comes from older designs that had mechanical aperture rings with notches at each stop (f/4, f/5.6, f/8, f/11, f/16 had my ancient Smena camera lens).

 

[KCook]

Link to another thread on camera basics -

Modes - Canon Rebel T6

Kelly Cook

 

[PhotoTeach2]

with regards to lenses, what does the term “stopped down” mean? Apologies if this question isn’t clear.

"Stopping down" generally refers to reducing the size of the lens's aperture.

A 100mm f/2.8 lens has a maximum aperture of f/2.8. However, frequently we will shoot with a smaller aperture diameter.

We might say we are "stopping down" when we select a smaller aperture diameter (such as f/5.6).

Many cameras leave the aperture all the way open until we are actually taking the photo. At that point the lens "stops down" to the smaller aperture to take the photo, and then opens back up.

Many cameras allow us to stop down the lens without taking a photo. This is generally called "depth of field preview".

Background

The typical modern camera lens has a variable aperture. This is essentially a hole with an adjustable diameter. This allows the photographer to select what size hole to use. Larger apertures allow more light into the camera. This tends to reduce image noise, and allow shorter shutter speeds. However, the larger hole also results in shallower depth of field.

The shape of the aperture approximates a circle. The "f/stop" of a lens is the ratio of the focal length of the lens to the aperture's diameter. "F/4" is actually a mathematical equation that represents the focal length of the lens divided by 4.

F/2 is an aperture diameter half the focal length. F/4 is 1/4 the focal length. On a 100mm lens f/2 is a 50mm aperture diameter, and f/4 is a 25mm diameter.

Thus the largest aperture is the "smallest" number. In this context 4 is larger than 8.

When we say that a lens is an f/2.8 lens, we are saying that f/2.8 is the widest aperture available. Normally the lens stays at the widest setting until you take the photo. This lets in the most light for the DSLR viewfinder, and yields less noise on a mirrorless viewfinder.

As depth of field is shallower at the widest aperture, it makes sense for the camera to focus at the widest aperture, and then stop down for the photo. (there are disadvantages here as some lenses shift focus when they stop down).

Once Again, (as always), Mr. Fryd has the two best answer-posts above.

 

[Ellis Vener]

I should have expanded on the question. What is a specific instance where you might need to stop down? When does stopping down come into consideration? Thank you.

you “stop down” a lens mostly when you want a greater depth of field.

To get a little techie for a moment, lenses are design so that they focus at a distance you determine. This means that when you are wide open everything that is in a plane that is parallel to the sensor will be in sharp focus but the greater distance an object is from that plane the more out of focus it will appear to be out of focus.

by making the aperture (opening) in the lens smaller, the more those objects that are in front of or behind that plane of focus will appear to be in focus.

Stopping down (making the aperture smaller) reduces the amount of light coming through the lens so if you want the camera to record the same volume of light you will either need to expose for longer, raise the ISO, or a combination of the two.

 

[Dem Bell]

It means "not wide open".

Example: if you are shooting an f/2.8 lens at f/4 or f/5.6, you "stopped down" by respectively 1 or 2 stops.

 

[Displaymyname]

Thank you.