Tack-Sharp Images Using the Reciprocal Rule :: Digital Photo Secrets

Tack-Sharp Images Using the Reciprocal Rule

by David Peterson 8 comments

Intermediate With all the rules and laws for photography, it's a wonder who came up with them. Just like rules, some are made to be broken, with a creative influence, while others are better off being followed. The Reciprocal Rule is one that ought to be followed. It is a relatively simple rule once you wrap your head around it. What is means is that to be able to handhold your camera without any recognizable camera shake, and thus blurring, in the image, the shutter speed should be at least the reciprocal of the focal length of the lens you're using. Sounds complicated, but it's really not in when you apply it.

Here's the 1 to 1 breakdown: Let's say you're photographing a friend's portrait and you put on your 50mm lens, to apply the reciprocal rule, you would need a minimum shutter speed of 1/50th sec to capture a tack-sharp image. Now let's say you're photographing the same friend's kids playing in a sandbox. You don't want to get too close, thereby distracting them, so you attach your 70-200mm telephoto lens. Applying the same rule, you would need to shoot at a minimum of 1/70th sec at 70mm and 1/200th sec if you're zoomed in at 200mm.

If you follow the Reciprocal Rule, there will most definitely be times when you will need to bump up the shutter speed to meet the "requirements" in order to have that sharp image.

There are best 3 ways to increase your shutter speed, and they all have pros and cons:

Open up the Aperture

An open aperture allows more light in, which lets you increase your shutter speed. As such, a small f-stop has a wider aperture opening, resulting in a shallow depth of field. Whereas a larger f-stop has a smaller aperture and a greater depth of field. So, keeping this in mind when you're playing with shutter speeds will help you determine how far you to with your f-stop in order to achieve the depth of field you want. It's all about balancing the shutter speed and aperture to achieve the best results. That's why it's a good thing that we have other methods for raising shutter speeds if we don't want to go low on the f-stop.

Increase the ISO Setting

Most people think to increase the ISO in low light situations, but there are times in brighter situations where you still may need to do so in order to match your focal length with your shutter speed. Keeping in mind that the higher the ISO, the grainier your image will be is the best guide for using this tweaking. If you can keep it at 400 ISO or less, you won't be faced with as much noise in your images. However, sometimes that is exactly the results you want. It will come down to your creative genius to determine if a higher ISO is the best way to go to allow for that faster shutter speed.

Use a Flash


Bright lights! A flash probably has the most impact on results when used to increase shutter speed. There are times when a flash makes all the difference, like a fill-flash to fill in unwanted shadows on faces, but there are also times when you really just want the softer lighting and might opt for changing your aperture or ISO instead.

If none of these three settings are an option, the non-setting option is a tripod. A tripod will give you the stability you need to keep camera shakes at bay.

One last note: you shouldn't rely on your camera's LCD preview to determine an image's sharpness, unless it's completely obvious. The LCDs are a tool to use as a preview screen, but later when you're at home uploading your images, the results are often a bit different and any signs of image shake will be more apparent.

The Reciprocal Rule is a handy guide and an easy ‘rule’ to follow compared to some of the other photography ones. Since with photography we are allowed to break the rules, this is one that can be broken, but better to follow it!

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  1. Larry Coleman says:

    Invaluable and simple rule. The best.
    I do often use the LCD to preview sharpness...but I use my camera's zoom button which gives a 10:1 zoom and lets me examine sharpness in detail.

  2. Mahen says:

    Excellent article, thanks alot

  3. Cecilia Prest says:

    Great article thanks David. I had the same question re smaller sensors but even that has been answered. This rule has certainly made a world of a difference to the sharpness of my bird shots - something I have been struggling with for years and thanks to you I now have the solution!
    Thanks for your generosity in sharing so much for free with amateurs like myself.
    Much appreciated,

  4. bob craft says:

    how about a step by step backbutton focusing using Nikon D-90

  5. David Peterson says:


    No, you don't need to do the conversion, unless you're using a film lens with your digital (smaller sensor) camera. The lens manufacturers have already done that conversion for you on the lens.


  6. Joe Darmiento says:

    What about when using a camera with a cropped sensor (like Canon Rebel series)? Should one convert to the equivalent full frame focal length before applying the reciprocal rule?

    • salsaguy says:

      Yes if you are on a cropped camera and use a 50mm lens you need to multiply by the crop factor (x1.5 for Nikon and x1.6 for Canon typically) so the 50mm lens is now an 85mm or so and so you'd need to use a shutter speed of around 1/100 to ensure no blur. On a 100mm lens then it becomes a 160 lens for Canon so use 1/200 to be sure. This assumes you don't have Image Stabilization which can help allow you to use slower shutters than the normal reciprocal rule would allow.

  7. Jocelynne Littlebear says:

    Thank you for your kind and expert services and communications. Much valued and appreciated.


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About David Peterson
David Peterson is the creator of Digital Photo Secrets, and the Photography Dash and loves teaching photography to fellow photographers all around the world. You can follow him on Twitter at @dphotosecrets or on Google+.