Stops

[clanthar]

This should be one of the first things a beginners learns after buying a camera, it's the first thing they teach at college

Yep, first thing I teach.

And now to make this more fun:
How many stops in a photographic print?
How many stops in a landscape? Sunny day? Overcast day? Backlit?
How many stops can your camera capture? RAW? JPEG? FILM?
Can your camera capture all the stops in the scene? What if it can't?
How many stops on your display? LCD? CRT? Laptop?
Is the range of stops on your display the same as the range of stops in a print?
Is the range of stops your camera captures the same as the range of stops in a print?
Is the range of stops in a print more, less or the same as the range of stops in a scene?
What if the scene has more stops than the print can hold?
What if the scene has less stops than the print can hold?
What if all of the above are different?

Joe

I never went to school. But I want to learn.

Are you being sarcastic in all this lol?

ETA: Finished reading it all..lol. Why did i even ask?

Not being sarcastic at all; those are some of the really critical questions. For example a photographic print has a range in "real" stops (darkest ink made on whitest possible paper) of less than 5 stops -- barely 4.5. The range of tone black to white in a sunny day landscape can be 10 stops. Can our cameras capture 10 stops? If they can, how do we stuff 10 stops of tone onto the print? Clearly we can't -- what happens?

In the transfer process from input (landscape, portrait, sports action, etc.) through camera, computer display, software, printer, to output print those stops are being passed through from one mismatched medium to another. Success results from an informed ability to manipulate that process. And making that process more manageable is the application of a consistent unit of measure which you brought up: the stop. You have your hand on the key and the key is in the door.

Sorry, I'm sounding like a teacher. There's a book to write to answer those questions. Many of the pitfalls you see folks encounter in photography have to do with the answers to those questions.

Joe

 

[clanthar]

Maybe a little history to help with the term:

Way back in the mid 19th century lenses didn't have adjustable irises. They had a slot cut into the middle of the lens and variable apertures were achieved by sliding metal plates into the slot. Different plates had different size holes in them and those plates were called lens stops. They stopped a portion of the light. Those evolved into adjustable f/stops -- a mechanical iris in the lens. Then the term stop took on it's additional meaning; the factor of change x2.

Quickly (by early 20th century) photographers caught on to the advantage of having a uniform unit of measure and the term stop was applied across the board not only to the controls of the camera but to the lighting of a scene and work in the darkroom. When students used to bring me prints from the darkroom I'd always give guidance in stops; "make it 1/3 stop darker," They'd say, "I made it for 12 sec. how much more?" And I'd force them to do the math to come up with 4 sec. more, and I'd insist on always talking in stops.

The advantage of a single measurement unit can't be overstated. What good is it to you to walk into XMart and have the sales person tell you an LCD display has a contrast ratio of 500,000 to 1? How many stops is that?

Joe

 

[SabrinaO]

Maybe a little history to help with the term:

Way back in the mid 19th century lenses didn't have adjustable irises. They had a slot cut into the middle of the lens and variable apertures were achieved by sliding metal plates into the slot. Different plates had different size holes in them and those plates were called lens stops. They stopped a portion of the light. Those evolved into adjustable f/stops -- a mechanical iris in the lens. Then the term stop took on it's additional meaning; the factor of change x2.

Quickly (by early 20th century) photographers caught on to the advantage of having a uniform unit of measure and the term stop was applied across the board not only to the controls of the camera but to the lighting of a scene and work in the darkroom. When students used to bring me prints from the darkroom I'd always give guidance in stops; "make it 1/3 stop darker," They'd say, "I made it for 12 sec. how much more?" And I'd force them to do the math to come up with 4.5 sec. more, and I'd insist on always talking in stops.

The advantage of a single measurement unit can't be overstated. What good is it to you to walk into XMart and have the sales person tell you an LCD display has a contrast ratio of 500,000 to 1? How many stops is that?

Joe

- oh im sorry. You were still talking?....

 

[clanthar]

Just had that second thought -- I'm finished.

Joe

 

[SabrinaO]

A "stop" is simply the de facto unit for exposure. It's nothing more than a doubling or halving of the value. Aperture, shutter-speed and ISO are all commonly expressed in stops. A change from 1/125 to 1/250 is a change in shutter-speed of 1 stop. Needing one stop more light would be the opposite, say a change from 1/1000 to 1/500 of a second, or from f8 to f5.6, or even ISO 400 to ISO 200.

Thank you! So when people say they are going to underexpose by a stop... they could mean they can do it by either aperture, ISO or shutterspeed... ?

If a person wanted to, or needed to, a one-stop underexposure could be accomplished by lowering the ISO 1/3 of a stop, by speeding the shutter up 1/3 of a value, and by closing the lens down 1/3 of an f/stop.

Just so i'm 100% clear... when someone needs to underexpose a stop, are they doing just one of these examples or all??
ex. Lower the ISO a stop + speed up the shutter a value a stop + close down the lens a stop = underexposing a stop.

 

[SabrinaO]

Just had that second thought -- I'm finished.

Joe

im still trying to figure out if you are being serious...lol

 

[GooniesNeverSayDie11]

Just to try and help you understand more, when you are in your semi-auto modes ( like Av and Tv mode on Canon, and uhhh I think S and A?? modes on Nikon??? ) if you are in lets say Shutter Priority, if you adjust the exposure comp for an underexposure, the camera will stop down the lens because it knows you want the shutter speed to be what you chose. If in Aperture priority mode, it will speed up the shutter. Both would be done by "Underexposing" on the exposure comp wheel, but would be achieved by different settings.

 

[SabrinaO]

Just to try and help you understand more, when you are in your semi-auto modes ( like Av and Tv mode on Canon, and uhhh I think S and A?? modes on Nikon??? ) if you are in lets say Shutter Priority, if you adjust the exposure comp for an underexposure, the camera will stop down the lens because it knows you want the shutter speed to be what you chose. If in Aperture priority mode, it will speed up the shutter. Both would be done by "Underexposing" on the exposure comp wheel, but would be achieved by different settings.

I shoot 100% manual. So to stop down an exposure, would I need to underexpose all three? (ISO, Shutter, Aperture)

 

[GooniesNeverSayDie11]

To underexpose you could use any specific one or a combination ( which is what Derrel was trying to illustrate ) If your ISO needed to be at 800 for proper exposure at 1/1000th and f/5.6 ( lets say you were shooting some fast action but wanted to get some background in the DOF but wanted it slightly blurred ) Therefore you wouldn't want to stop down the lens cause you might lose that slight Bokeh you liked, so you could either up the shutter speed ( since you are trying to freeze action anyway ) or lower the ISO from 800 to 400 ( which would get you less noise, although underexposed areas are prone to more noise, so it may not matter much )

 

[clanthar]

Just had that second thought -- I'm finished.

Joe

im still trying to figure out if you are being serious...lol

I'm serious -- no sarcasm, no joke.

 

[clanthar]

Just to try and help you understand more, when you are in your semi-auto modes ( like Av and Tv mode on Canon, and uhhh I think S and A?? modes on Nikon??? ) if you are in lets say Shutter Priority, if you adjust the exposure comp for an underexposure, the camera will stop down the lens because it knows you want the shutter speed to be what you chose. If in Aperture priority mode, it will speed up the shutter. Both would be done by "Underexposing" on the exposure comp wheel, but would be achieved by different settings.

I shoot 100% manual. So to stop down an exposure, would I need to underexpose all three? (ISO, Shutter, Aperture)

If you're shooting in manual then you're probably adjusting either shutter speed, f/stop or ISO until the meter zeros. Your camera meter is likely marked off in 1/3 stop increments with zero in the middle. Each mark up or down from zero is 1/3 stop -- three marks and you're at 1 stop under or over. To underexpose 1 stop adjust any one or all three controls (shutter, f/stop, ISO) until the meter indicates -1. To overexpose 1 stop do the same until the meter indicates +1. 1 stop more is twice the amount of light and 1 stop less is 1/2 the amount of light from what your camera meter has determined is correct exposure.

Why would you do it? Under what circumstance would you override your camera's meter and take a photo that is -1 stop underexposed or +1 stop overexposed? If you have good reason to select an exposure that is -1 in conflict with the camera's meter then isn't that the correct exposure and wasn't the camera overexposing 1 stop and you corrected the camera's error?

Joe (I'm serious)

P.S. Are you using the camera's internal meter? If you're shooting in full manual mode then you're using external strobes? I believe Derrel noted earlier that strobes can also be adjusted to vary the exposure, but in that case how are you determining exposure? Are you using an external light meter?

 

[TexasAggie07]

Thanks for all the explanations and history! Great stuff!

 

[Vtec44]

Well, yes and no Sabrina. When a person says, "try stopping the lens down," or "you need to stop down more", or "try stopping down more next time", that is referring to the LENS aperture. "Stopping down" the lens means closing the lens diaphragm "down", from a wide aperture like f/2.8, to a narrower, smaller aperture, like f/5.6 or f/8, for example. "Stopping way down" would be closing the lens diaphragm down quite significantly, to say, f/16 or f/22 with a conventional lens; on a view camera lens, stopping "way down" is usually in the f/64 to f/256 range. The opposite is "opening up" the aperture, and shifting from a small, narrow aperture, to a wide, big, light-admitting aperture.

This is my understanding of the term "stopping down" also. Unless specifically mention ISO or shutter speed, "stopping down" means reducing the size of the aperture.

 

[clanthar]

Well, yes and no Sabrina. When a person says, "try stopping the lens down," or "you need to stop down more", or "try stopping down more next time", that is referring to the LENS aperture. "Stopping down" the lens means closing the lens diaphragm "down", from a wide aperture like f/2.8, to a narrower, smaller aperture, like f/5.6 or f/8, for example. "Stopping way down" would be closing the lens diaphragm down quite significantly, to say, f/16 or f/22 with a conventional lens; on a view camera lens, stopping "way down" is usually in the f/64 to f/256 range. The opposite is "opening up" the aperture, and shifting from a small, narrow aperture, to a wide, big, light-admitting aperture.

This is my understanding of the term "stopping down" also. Unless specifically mention ISO or shutter speed, "stopping down" means reducing the size of the aperture.

Yes, but the original question was: "I know what f/stops are... but what are people referring to when they say they are going to underexpose ambient light by a stop? Or when someone says they need a stop of more light?"

In which case a stop is a unit of measure used by photographers -- factor 2. F/stops and a stop are related terms. Stopping down the lens from f/8 to f/11 reduces the amount of light by 1 stop. The light volume is halved. Decreasing the shutter speed from 1/60 sec. to 1/30 sec. increases the exposure by 1 stop. The light volume is doubled. Determining correct exposure (shutter and f/stop) for ISO 400 and then making that exposure with the ISO set to 200 overexposes by 1 stop.

F/stop and stop are related, but not the same. All measurement of light and exposure in photography should be done in stop increments. We have a standard unit of measurement that allows us to manage what we do. We measure light in stops.

Joe

 

[Vtec44]

Yes, but the original question was: "I know what f/stops are... but what are people referring to when they say they are going to underexpose ambient light by a stop? Or when someone says they need a stop of more light?"

Well I wasn't disagreeing with the explanation of a stop unit. I was just saying that Derrel's stopping down is exactly my understanding of that term.