The Focal Length vs Shutter Speed Rule
During a recent webinar I briefly touched on a rule of thumb that I’ve used for years. It connects the focal length of a lens and the shutter speed of the camera with the sharpness of a photo. It generated a few questions so let’s get some answers.
Camera shake vs motion blur
Camera shake is where the camera moves, motion blur is were the subject moves and they’re two very different things. In this post I’m focusing just on camera shake, in other words where you photograph a static subject such as a landscape or seated portrait with a handheld camera. Getting sharp shots of speeding cars is another skill all together.
The rule of thumb
When I started in photography the rule of thumb was really simple. When hand holding your camera the shutter speed should match or exceed the lens focal length. In other words if you wanted a sharp, shake free shot with a 50mm lens your shutter speed would be 1/50th sec or faster.
Whilst that was fine in its day the world has moved on and so has my rule. Modern lenses and cameras are capable of recording very fine detail and as we all love to zoom in close we view our images with a more critical eye. Add to the mix all the different sensor sizes that will alter the effective zoom of the lens and you’ll understand why the old rule needs updating.
The new rule of thumb
Today I use the rule of thumb that the shutter speed should be double (or more) then the lens focal length. In other words if you were using a 50mm lens your shutter speed would be 1/100th sec or faster.
To put that into the language of real world photography, if I’m using my 10mm fisheye I’m happy to shoot all the way down at at 1/20th second shutter speed but if I was shooting with a 400mm lens I’d want a whopping 1/800th second shutter speed. Which might be tricky and brings me onto my final point.
Bend the rule
Some rules are set in stone but others can be bent or broken, my rule of thumb is the later.
Does your lens have an image stabiliser (shake reduction) system, are you really good at holding your camera and is your camera a full frame sensor or bigger? If so then you can bend this rule a little, to a lot. If you use a tripod then you can totally break this rule as long as nothing is moving in your scene of course.
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Also with todays digital cameras we can tweak sensitivity to get a higher shutter speed and as things move forward higher ISO’s are becoming more useable, unlike the old film days!
I don’t agree. Color and dynamic range would be limited, also noise would be increased. Depending what’s the purpose of your shooting, you maybe can accept those facts – but they are there.
Yes there is a downside but realistically ISO performance of modern cameras is leap years ahead of digital cameras of 5 – 10 years ago. As a result higher ISO’s are useable, and can be a “get out of jail” option.
Mark, I was in your camp for a long time and part of me (the nerd) really wants to stay there, but we have actually gotten past the need to “expose to the right” with the best of kit out there. I don’t bother with ETTR anymore. I evaluated my camera with RawDigger and found that I sometimes have to bracket down a bit instead of going the other way. You just gotta know your gear and your personal tolerances.
What about IS do you not feel that the old rule still works with IS ? I think I can still hold a shot at much slower speeds with the good IS that canon has.
Agreed Chaz. As I mention in the last section IS allows the rule of thumb to be bent and you’re the best judge of how low you can go 🙂
Iv been following the old rule for years. Your advice about doubling it is interesting, and something I shall try, thank you.
Hi Gavin
From my experience there is one more factor to take in consideration especially nowadays where the mega pixel sizes go through the roof. The bigger the MP count in a sensor there is gonna be more visible blur due to camera shake. I compared Nikon D600 and D800 with 300mm lens shot from tripod at 1/30 sec with a 2 sec self timer. Lens was set at minimum focusing distance to better represent the test. The mirror would produce camera shake at that speed so tiny but still visible at 100%, because of focal length. Then comparing both pictures 36 MP had more blur than 24MP because the whole scene looked bigger. If I cropped D800 picture to 24 MP the blur appeared to be the same. Same thing happens when shooting stars at night, the more MP the shorter exposure has to be if you want not to have star trails. This only applies off course if you look at the full size files at cameras native resolution or pixel peeping.
Have a nice day
G’day Gavin.
What an interesting subject! I have long suspected that you needed a faster shutter speed but have been blaming getting old for the not quite so clear pictures. I do try to use a tripod wherever I can and trigger the camera using remote or my CamRanger. I do a lot of Chromakey work where you are really governed by the power of the constant lighting. Where ever possible I will even use a tripod for scenery. Thank you for an interesting article and sharing these things with us.
Barry from Tassie.
Thank you Gavin for this interesting article,
I have been working with a similar principle as yours, I have a 7D which as you know is not a full frame so I work with the shutter speed should be the focal length times by the crop factor of the sensor, ie 400mm focal length times by 1.5 crop factor equals 1/600 th of a second. I was wondering if you have hears of this method and what is your opinion on this method.
Regards Rhys
Rhys, In my opinion, you are correct in your calculations. Few people add the crop factor in determining their shutter speed, but it is essential in getting an idea of the shutter speed required. Gavin’s method of doubling the focal length makes the rule a little bit less of a mathematics test. Granted Gavin,s method results in a somewhat higher shutter speed, but the result is just a starting point for shutter speed, not a “carved in stone” kind of answer.
Hy Gavin,
You have mentioned that in the caso of a 400mm lens you don´t need to shootat 1/800. So what’s the limit focal length to double the speedin your new rule?
It’s a good rule to apply with any focal length but if in doubt check the shot on the camera LCD before walking away
So if your taking a group shot on a sunny day on a dx camera at 28mm with crop factor 1.5 42mm does my shutter need to be above 1/50 or 1/80? Also if you have to make the shutter speed faster to compensate for the suns brightness will I lose sharpness in the image if I take shutter speed higher?
This is interesting as I’ve been shooting cricket with a 90D and a 170-500mm Sigma f5.6/6 with no stabilizer built in. I’ve struggled on days when the light is low and I’ve played around lots with the settings. I do tend to bump up the IS to take account of the light and the best shots are usually on the brighter days. To get really sharp images I’ve also used a tripod, but you tend to need to follow the action so hand holding (which is near impossible to get sharp enough images) or a monopod is what I prefer. My main question is would I get better results by changing my body with this lens? or would you change the lens for something like the Nikon 200-500mm f5.6E ED VR AF-S Lens which I’ve seen some excellent reviews about? Any comments on this? Would a Nikon D600 or 700 give me more scope to play around with the IS?
It sounds like you’re suffering from motion blur, so a tripod isn’t going to help much. Stick with your monopod and higher ISO. A new body might help but not as much as a better lens would.
What you need is more light hitting the sensor, so ideally a lens with a bigger aperture would be best. An f/4 lens would HALVE your shutter speed and faster shutter speeds = sharper photos. So your ideal lens is long, larger apertured and sadly expensive. I’ve not used Nikon lenses so can’t recommend a particular one. However I’d recommend borrowing (or hiring) the lens you think might work before investing 😉
Thanks for taking the time to write about this. I would mention one thing, though – the effects of camera shake are statistical, not absolute. In other words, says your lens is 50mm. At 1/500 there might be a 1% chance of a blurry photo. At 1/4 sec, the odd of having a blurry shot might be more like 90%. So, in your example, yes, at 1/60, the image was a bit soft. But had you taken 10-15 shots, one of them might have been perfectly crisp. Whereas at 1/125, you would only need to take 1 or 2 shots to get a good result.
Thanks Rob, I guess almost everything is statistical.