Shutter speed and f/stop ratio..

SmokyMtnHiker · Feb 12, 2014

I've been watching YouTube vids on photography; mainly Mike Browne's page.

I've heard him say something about a relationship between the shutter and the aperture f/stop. Kinda like a ratio of one to the other to reduce the chance of camera shake.

Can you elaborate on this? Or did I just misunderstand..?

Designer · Feb 12, 2014

I think it was focal length rather than aperture.

In short, yes, there is a relationship, but it has to do with exposure, not camera shake.

So to clarify; generally, you would not want to take a hand-held shot with any shutter speed slower than the inverse of the focal length. (ex.) hand-held shot, 50mm lens: 1/50 second, maximum.

astroNikon · Feb 12, 2014

you are asking about the basics of the Exposure Triangle.
Camera Exposure: Aperture, ISO & Shutter Speed

there's plenty of things to read online and here if you search

lennon33x · Feb 12, 2014

There is an inverse relationship between the two (numerically) for proper exposure. The faster the shutter speed (1/500 to 1/800 to 1/1000) the wider the aperture (the lower the number). An additional player in here is ISO, hence the exposure triangle. Check out Understanding Exposure by Peterson.

Think of it this way. Your sensor is a bottle and light is represented by water you pour into it. You place a funnel on it (the aperture) and you pour water into the bottle for a specific time period (shutter speed). Let's say you aren't getting to the right level with that particular funnel or speed you're pouring in water. In order to get to a specific level on the bucket (proper exposure), you need to either pour in water for a longer period of time or get a bigger funnel (i.e. wider aperture). This is an example of the relationship between the three.

JustJazzie · Feb 12, 2014

Designer said:
I think it was focal length rather than aperture. In short, yes, there is a relationship, but it has to do with exposure, not camera shake. So to clarify; generally, you would not want to take a hand-held shot with any shutter speed slower than the inverse of the focal length. (ex.) hand-held shot, 50mm lens: 1/60 second, maximum.

It sounds like this is what you are talking about. So if I were using a 200mm lens, I wouldn't want to use a shutter speed slower than 1/200 because the focal length magnifies shake. Have you ever looked through a telescope and noticed the slightest movement turns everything into a blurry mess? Same thing here.

Although from what I understand if you have IS, or anti shake, you can stretch the rule and go a bit slower than standard rule.

Derrel · Feb 12, 2014

I think you mean the 1/ over shutter speed idea, meaning if the lens focal length is 50mm, the shutter speed needs to be at least 1/50 second; with a 200mm telephoto, the shutter speed needs to be at least 1/200 second or faster. In today's digital age, many people feel that when using a high-resolution camera, like say a 24- to 36-megapixel camera, that the speed needs to be DOUBLED, so with a 50mm lens 1/100 second, with a 200mm lens 1/400 second. I myself feel that the double the length rule is a solid practice to follow.

Overread · Feb 12, 2014

I think you've mixed two different things together.

Shutter speed and Aperture are related as mentioned above by the others. They contribute toward the final photographic exposure along with the ISO setting.

The shutter speed is also related to the camera shake aspect. When you hand-hold a camera a rough rule of thumb is 1/focal length of the lens = minimum shutter speed to avoid camera shake. So if you're using a 50mm lens 1/50sec should not have any camera shake.

Now this assumes a few things:
1) Good standing posture - good posture is important as it helps maximise your stability; if you're holding the camera badly you're more likely to increase shake.

2) Fatigue/health - if you're tired or worn out your body is going to be less stable; as a result you'll find it harder to get a clear sharp shot if you're at the lower limit toward the rule of thumb shutter speed

3) 35mm sensor/film. The rule of thumb is devised around the 35m camera; significantly heavier cameras and those with a larger sensor will change the rule of thumb to a degree.

4) Static subject. Clearly this rule only applies to the camera shake; if you're shooting a moving target then the shutter speed requirements will be defined more by the subject than the camera holding. 1/500sec for a moving subject and any faster is ideal.

KmH · Feb 12, 2014

Shutter speed should be no longer (time wise) than 1/the focal length of the lens. 1/the focal length of the lens is a ratio.

So with a lens focal length of 50 mm you want the shutter speed to be no slower than 1/50 when shooting hand-held
with a 200 mm focal length you want the shutter speed to be no slower than 1/200.

However, if you can add some support - short of a good stable tripod - to the camera in addition to hand holding it, you can usually use a longer shutter speed.

Plus there is good hand holding the camera technique, and bad hand holding the camera technique.
Da Grip « Joe McNally's Blog

KmH · Feb 12, 2014

Gavjenks · Feb 12, 2014

Agree with Derrel.

It seems obvious that what you are talking about is the 1/focal length rule. This rule was from a long time ago, though, when:
1) People were much less pampered by autofocus and image stabilization, and knew how to brace their cameras better. And
2) People didn't pixel-peep as much. Or I guess "grain-peep." Still happened, but not as rampantly I don't think.

Thus yes, you are better off doing 1/(focal length * 1.5 or 2)
If shooting a STILL subject with image stabilization on, it's more like 1/(focal length DIVIDED by 2 or 3)

JacaRanda · Feb 12, 2014

Should one factor in crop factor when using a rule of thumb like mentioned?

Braineack · Feb 12, 2014

JacaRanda said:
Should one factor in crop factor when using a rule of thumb like mentioned?

no, why would you?

Gavjenks · Feb 12, 2014

That is a good point Jaca. I would have to say yes. The cropped portion of the image will be shaking more in a "pixels traveled per shake movement" sense, with the same lens, since you have more pixels per portion of the image on a crop sensor (really it's a function of pixel pitch, but for a beginner's forum, crop factor is a good enough estimator of that)

Similarly, if you know ahead of time in the field that you will be cropping and blowing up the crop in software/printing, then use a proportionately faster shutter speed.