Help with Photography Question (Technical)

[tar]

Hi guys,

I've got a question that I hope you might be able to answer. I posted this on the main CA forums, and the folks there pointed me in this direction. As part of a project I'm doing at uni, I'm coding a camera app to be used on mobile phones. The idea is to improve the feedback that the user recieves through various means. One thing I'm looking at is indicating to the user that the photo they are taking is likely to be blurred due to them moving the camera too much.

My question is if you know the various settings of the camera, such as the focal length, shutter speed etc, is there a way to determine how fast the camera can move in a direction without the resultant photograph being blurred? For example, the phone I'm using has a focal length of 5.6 mm and a mechanical shutter speed of 1/1000~1/3 s.

The more technical details of photography are not something I know alot about, so I would really appreciate any help you guys could give, or if you could point me in the right direction to solve this problem.

Cheers

Chris

(I wasn't really sure which part of the forums to post this in. Photography Discussion seemed like the best bet, but if this is in the wrong place then feel free to move it.)

[Rhynome]

Hello! Aw, you made the jump.

Just so guys know, two people have already posted in the CA.org Lounge:

I believe that there is a universal answer for this.

From my experience, anything below 1/60th is likely to be blurred without the use of a tripod. Basically, shutter speed is the only value you'll need for this because its the only one that can affect the timeframe in which the sensor/film captures the image. (as aperture and ISO/ASA determine how much light, not how quickly).


well the old standard rule of thumb in hand held photography is 1/focal length.
so, if you shoot with a 50mm lens, anything shorter than 1/50 will be ok; if you're shooting with a 105mm lens, anything shorter than 1/100 or 1/125.

this is for the old 35mm cameras. there is argument about if the 'rule' changes with the cropped sensor cameras etc, and it also depends on your system: an slr (with a mirror that slaps up and down) will have more shutter vibration than a rangefinder.

a digicam held out in front of you will in general move more than a camera that is supported by both of your arms with elbows tucked in and held against your eye.

it also depends on individual technique and i don't know about how all the vibration/steadying/stabilizing features factor in in modern digi cams but, 1/focal length is the old rule of thumb...

If that makes it any easier for any of you.

[Grumbledook]

I was going to say pretty much what tensai said

of course a flash can help freeze motion to a degree but there is a whole other can of worms that go with this

like either over exposing the subject, or underexposing the background (not always bad)

quite a few flashes on camera phones kinda suck too (used to sell phones) they will be useless during the day for most situations

the 5.6mm focal length for your camphone is the equiv of 34mm on a 35mm so by that logic 1/30 or whatever is going to be the closest (diff camera set ups have different increments)

anything faster than that should be ok, depending on how steady you are holding it, though I don't think you are going to be able to detect that without gyros and things in the phone (can't see this happening any time soon)

hope that helps

[Morbid]

The 1/focal_lenght is a good rule for full frame cameras. But it depends on many other things, like the resolution of the sensor, the size of the sensor and most of all the person holding the camera.

I think it would be far too difficult to analyze so my suggesting is to just experiment until you find a shutter speed at which you can consistetly get sharp images. It should be a linear function of the focal lenght, so if you have zoom lens in the phone you could take that into account.

Edit:
If you have access to the sensor resolution and size of the sensor in the software that would be relatively easy to take into account aswell. If you double the linear dimensions of the sensor, the shutterspeed can be halved with the same result in sharpness. If you halve the linear resolution (pixels per mm), the shutter speed can again be halved.

[tar]

Rhynome: Yes I've made the jump over :) Would've done it sooner but I was busy with uni. These forums are really nice, might have to spend a bit more time here. Thanks for posting the replies from the other thread, that was a good idea.

Grumbledook: Thanks for the info. As for detecting how steady the camera is being held, the phone I'm using has a built in accelerometer that I can access, so getting this movement information is actually quite easy.

Morbid: Thanks man, thats useful stuff.

The info I'm getting from you guys is really helping, it gives me something to look into and get started on, so thank you all.

[Morbid]

Glad I could help, good luck on the project.