The other day I had a wedding with a second shooter/assistant. She has a brilliant eye for images, and it’s been a joy to work with her that day. However, she is still rather blind on the technical side of photography. Many of her photos – most of them well composed and balanced – were not sharp due to camera shake. Eeeek! I looked at the EXIF data, and yep, no wonder this has not been working: 1/25 sec exposure time with a 135 mm lens does not work. You simply can not shoot this photo from hand. Doesn’t work. You need a tripod.
When I explained this to her, after the shooting, she understood well the reasons for this. But she asked the inevitable question: “So, Mark, what times CAN one shoot from hand without camera shake?”
And I had to admit, that I had never given much thought to this, because I have shot probably hundreds of thousands of photos in my life, and I pretty much got a “feeling” for what I can shoot from hand, and what not.
But the question is a very valid question from beginners, and I gave it some thought. Finally, I came up with “Marks Anti Camera Shake Formula”:
Now, what does this mean, and why this formula?
Let’s take a look at each part of the formula, from left to right.
In the old days you used 35 mm slide film (a “full format” sensor if you want). The resulting image with a 100 ASA slide film would be crisp and sharp. Using a professional slide scanner you could extract an image of about 10 to 12 megapixel in size from the slide before it got all grainy. The rule of thumb for photographers was that you could manually shoot up to the reciprocal value of the focal length. In other words: If you had a 100 mm lens, you needed to shoot at 1/100 sec or faster to avoid the dreaded camera shake. If you had a 200 mm lens, you needed to shoot at 1/200 sec. You get the idea. Now, this turned out to be a very good rule, and many photographers got along with it for decades. This is the first part fo the formula.
Enter digital cameras. All of a sudden, your trusted universe of 35 mm cameras became fragmented. You had cameras with all kinds of sensors and resolutions.
Take crop sensors, e.g. Canon’s 1D mark II N with a crop factor of 1.3 (compared to full frame sensors), or Canon’s 30D with a crop factor of 1.6. These crop sensors change the rules, because they “prolong” the focal length. A 100 mm lens on a 1.3 crop sensor behaves actually like a 130 mm lens (on a full frame sensor). Thus, you need to take into account that you should shoot at 1/130 sec or faster, not at 1/100 sec or faster! This is the second part of the formula.
Finally, you have cameras that have a much higher resolution than your typical slide film, e.g. Canon’s 1Ds mark III with its 21 megapixels. With higher resolutions you need to be faster than with slide film, because the old rule was based on a resolution of 10 to 12 megapixel, not 16 or even 21 megapixel. Where in the past the camera shake would “disappear” in the film grain, it now becomes visible in the digital image. This is the third part of the formula. Here, the formula is a bit shaky, because I did assume that in the past slide film had a resolution of 10.5 megapixel. Depending on the type of film and scanner, the resolution could be higher. I think 10.5 megapixel is a good value though, and as beginner you will be on the “safe side” using this value.
Now just try the formula for yourself. Try to calculate the maximum exposure time for a 135 mm lens on a 1.3 crop sensor with a 10.1 megapixel camera. It’s 1/200/1.3×10.5/10.1 = 0.003998476… Hmmm. Now, this is the exposure time in decimals, which is not very handy. On the calculator, just press the 1/x button to see a value that you can actually use: 250.09523. Bingo! With this lens/camera combination you need to shoot at 1/250 (or faster) to get rid of any camera shake.
So, when the time depends on the lens and the body, there seems to be no easy rule of thumb any longer, right? Right.
But wait! Mark comes to the rescue!
In order to make it easier for those of you shooting with DSLRs for the first time, I compiled a handy Excel sheet that lets you enter your camera values (in blue) and calculate the maximum exposure time. Please note that the resulting times are a little odd; you probably can not set your camera to shoot 1/62 sec, but that’s not needed anyway. In this cases I’d go with 1/60 and see what happens. After all, it’s still just a rough guide to what you can expect to shoot safely from hand. For your convenience, the sheet also provides you the estimated “rule of thumb” for that camera, i.e. how the exposure time relates to the focal length.
For those of you who are operating Canon cameras, namely the 1Ds mark III, 1D mark III, 5D, and 30D (like we do), I went a step further and rounded the results to the nearest exposure times that the camera offers. I realized that the 1D mark III, the 5D, and the 30D are very very close to each other. The crop factors and image resolutions average out almost exactly, so I put those three bodies into one rule:
So, the new rules of thumb -for our cameras- are:
- 1Ds mark III – 2x the focal length (200 mm means 1/400 or faster)
- 1D mark III, 5D, 30D – 1.25x the focal length (100 mm means 1/125 or faster)
And by the way, some of you may find that they can hold the camera more steadily and shoot photos without camera shake at slower speeds than indicated in the table. Congratulations! Go ahead and modify the list to cater for your style. The list is just meant as a starting point for those who wonder why the heck they can’t get any decent pictures from their brand new DSLR that was advertised as the best thing since sliced bread?
Hope this helps.
P.S.: Just realized that I did not mention lenses as part of the equation. The above rules are just valid for lenses that do NOT have an image stabilizer. Lenses with an image stabiler compensate for the camera shake considerably, and thus you might have to introduce yet another factor into the formula.