# Taking a digital picture of a spinning fan... **URL:** \ **Category:** Factual Questions\ **Created:** [October 30, 2006, 6:31pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461 "2006-10-30T18:31:17Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![black\_rabbit](https://avatars.discourse-cdn.com/v4/letter/b/f19dbf/32.png) [@black\_rabbit](https://boards.straightdope.com/u/black_rabbit)\ **Post date:** [October 30, 2006, 6:31pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/1 "2006-10-30T18:31:17Z")
If I were to use a typical consumer digital camera to take a photo of a fan that was running at 2500-5000 RPM, would the fan appear to be “still”? IE, given the CCD speed in a consumer model camera, would a photo of the blades of a running CPU fan look blurred or sharp? Yes, this about a possible Ebay ripoff. Unfortunately, I don’t have a camera handy, otherwise I’d experiment for myself. I’ve also got no idea how to do the math to figure out shutter speed vs. rpm, because I’m a big dummy. Thanks. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [October 30, 2006, 7:19pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/2 "2006-10-30T19:19:41Z")
Yes and no. It will depend entirely on the ISO, Shutter speed, Aprature and possibly most important, if a flash was used. Yes, you can stop the action of fan (I did it just a few days ago with a cheapo camera) and you can leave the motion in. BTW what is the ebay issue? ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [October 30, 2006, 7:24pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/3 "2006-10-30T19:24:34Z")
If a Canon PowerShot S70 counts as “typical consumer”, you bet your ass you can get pix in which the blades appear totally still. And well-focused enough you can see the dust bunnies sticking to the frozen-in-motion blades. [http://home.earthlink.net/~ahunter03/Stuff/FanFragment.jpg](http://home.earthlink.net/~ahunter03/Stuff/FanFragment.jpg) You can also (using different settings, natch) get an artistic blur, not only from spinning fans but things moving a whole lot slower. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 30, 2006, 7:24pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/4 "2006-10-30T19:24:43Z")
A fan running at 500 rpm travels 4.3 degrees per millisecond. ---
**Author:** ![black\_rabbit](https://avatars.discourse-cdn.com/v4/letter/b/f19dbf/32.png) [@black\_rabbit](https://boards.straightdope.com/u/black_rabbit)\ **Post date:** [October 30, 2006, 7:41pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/5 "2006-10-30T19:41:17Z")
Hmmm. Oh well. There goes one argument in our favor. The boss bought a mobo/CPU combo off of Ebay, and it was DOA. The seller sent us a pic of the board sitting in front of a monitor, hooked up to a PSU, and (supposedly) POSTing. Noting that the CPU fan didn’t appear to be spinning, he asked me to dig in to it. I’ve got to admit that he’s being a little tenacious over 40 bucks - and it’s his fault for buying production components off of Ebay - but still. Thanks folks. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [October 30, 2006, 7:45pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/6 "2006-10-30T19:45:36Z")
[QUOTE=black rabbit] If I were to use a typical consumer digital camera to take a photo of a fan that was running at 2500-5000 RPM, would the fan appear to be “still”? IE, given the CCD speed in a consumer model camera, would a photo of the blades of a running CPU fan look blurred or sharp? Yes, this about a possible Ebay ripoff. Unfortunately, I don’t have a camera handy, otherwise I’d experiment for myself. I’ve also got no idea how to do the math to figure out shutter speed vs. rpm, because I’m a big dummy. Thanks. [/QUOTE] Yes, it is possible, especially if the picture is flashed, as flash durations generally range from 1/1000 - 1/20,000 of a second, depending on the power of the unit and the power outputted. If it’s an indoor photo, and there is no evidence of flash, then I would assume the fan is most likely not running. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [October 30, 2006, 7:48pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/7 "2006-10-30T19:48:45Z")
[QUOTE=pulykamell] Yes, it is possible, especially if the picture is flashed, as flash durations generally range from 1/1000 - 1/20,000 of a second, depending on the power of the unit and the power outputted. If it’s an indoor photo, and there is no evidence of flash, then I would assume the fan is most likely not running. [/QUOTE] If you have a copy of the picture, it’s possible that the EXIF information is still intact, and that would tell you all the settings of the camera used. I wouldn’t bet on the information being there, but it’s a distinct possibility. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 30, 2006, 7:50pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/8 "2006-10-30T19:50:21Z")
[QUOTE=Squink] A fan running at 500 rpm travels 4.3 degrees per millisecond. [/QUOTE] You seem to have messed up something in there; the correct figure is about 3 degrees per ms. I also double-checked [here](http://www.engnetglobal.com/tips/convert.asp?catid=8). ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 30, 2006, 8:02pm UTC](https://boards.straightdope.com/t/taking-a-digital-picture-of-a-spinning-fan/378461/9 "2006-10-30T20:02:44Z")
[QUOTE=Q.E.D.] You seem to have messed up something [/QUOTE] Yup. I probably had the calculator set for metric radians or something.