Rule of thumb...how to get the best sharpness?

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You have to take the 1/focal length rule with a pinch of salt when dealing with a compact digicam. Let's forget about the focal lengths and crop factors for a moment and take a step back and look at what's happening.

You can't hold any camera perfectly still, that's just a fact of life, so as a result the lens is waggling about (albeit small amounts) while you frame the shot. That waggling is over a certain angle range so as you increase the focal length that waggling becomes more apparent due to the reduced angle of view. Now if you use a slower shutter speed the waggling causes camera shake (or blurring as we're calling it), the longer the focal length the more obvious the shake because the waggling angle is a bigger proportion of the angle of view.

So how do we reduce shake? You need to use a shutter speed which effectively "stops the action" in the same way as you'd want a higher shutter speed to freeze a footballer heading a ball for example. At longer focal lengths the waggling is more pronounced - the action is faster - so you need a higher shutter speed than at shorter focal lengths.

On 35mm systems trial and error has determined that for most situations, most people and most cameras that a shutter speed of 1/focal length is enough to prevent camera shake. With good technique etc that can be reduced hence it's only a rule of thumb.

For compacts it's a bit of a different ball game. The focal lengths are shorter but the posture for holding the camera is different, you don't really have the ability to brace elbows and squash the camera against your face to stabalise it. Therefore the 1/focal length rule doesn't necessarily apply. However, if you use the 35mm equivalent focal length then you do get a 1/focal length speed which you can have a good chance of hand holding.
 
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It's all about magnification so of course the crop factor must be taken into consideration.

SDK^ said:
This always comes up and it's not necessary to match shutter with a crop factor camera.

SDK^ said:
Canon 1Ds, 50mm 1/50
Canon G7, 8mm (50mm equiv) – 1/50

You've just contradicted yourself there.

As Hoodi pointed out the 60mm focal length on my Fuji is the equivalent (i.e. taking into acount the crop factor) of a 300mm lens so I have no chance of hand holding it at 60mm. I have to take into account the crop factor and choose a shutter speed of 300mm, as you've just pointed out above.
 
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You don't have a crop factor in that camera, it has a lens which is matched with it's sensor.

Read my post above, compact cameras are totally different to 35mm ones in how you hold them etc so you can't apply the rule of thumb in the same way.
 
Soldato
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Mohain said:
You've just contradicted yourself there.
I have to take into account the crop factor and choose a shutter speed of 300mm, as you've just pointed out above.
Wrong - you have take into account that you're not using a 35mm lens ;)
How many times do I (we) have to say this - The rule is for 35mm lenses !!! :)
 
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SDK^ said:
Wrong - you have take into account that you're not using a 35mm lens ;)
How many times do I (we) have to say this - The rule is for 35mm lenses !!! :)

The rule is for 35mm lenses exposing to a 35mm film sized area, not an APS film sized area. It does make a difference.

If I was to put a 200mm lens on my 35mm film body I'd get a certain magnification and I'd choose a certain shutter speed to ensure sharp hand-held images. If I put the same lens on my 30D I get a larger magnification, I'm getting more camera shake, so I have to increase my shutter speed to get sharp hand held images. To take it to extreme, if my 30D had a 20x crop sensor (for arguments sake) and I put the the 200mm lens on it I'd get an enormous magnification and the camera shake would be much more apparent, so I'd need to increase the shutter speed significantly to ensure sharp hand held images. :)
 
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It's a crop factor it's not magnification!

You don't shake more just because you're using a 20D rather than a 5D.

rpstewart said:
The focal length doesn't change, it's just a crop out of the centre of the image circle. If, for example, you shot 1/50s at 50mm on a full frame camera and it was sharp then it's still sharp when you crop out the centre portion - this is all that happens in a 1.6x body.
 
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LOL! This thread has had me laughing most of the morning.

I hope this will help you understand what a crop factor is and why it is not actually magnifying anything even if people use that term (incorrectly).

This was originally posted by SDK^ a long time ago but can't find the original link so I hop SDK^ or whoever made it doesn't mind me re-hosting it:

1.6-crop.jpg
 
Soldato
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Mohain said:
The rule is for 35mm lenses exposing to a 35mm film sized area, not an APS film sized area. It does make a difference.

bang.gif
bang.gif


Read the thread from the start !!!

Thanks for the lesson on crop factor up there :p
Like rpstewart and ^^Gord^^ also said - you need to understand that on an APS-C camera it’s a crop not magnification ;)
 
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