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On 2008-11-04 19:04:23, Raiderski wrote:
you're misleading two things which are focal length and aperture size. simplest possible, and to be honest not very nice, explanations are:
1. focal length controls angle of view and zoom. shorter length = wider angle of view, longer length = narrow angle of view (which also means big zoom)
2. aperture size controls amount of light reaching the sensor. bigger value = less light
both values are constant which means no fun - no zoom, no aperture size vs. shutter speed combinations
should I include pictures as examples?
Yes do.
[ This Message was edited by: bishshoy007 on 2008-11-06 10:25 ]
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Posted: 2008-11-06 11:24:59
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On 2008-11-04 19:10:32, number1 wrote:
Would explain, why my c702 1/5 iso640 pics are a tad darker than my old k800i 1/5 iso 640 pics
Just because the aperture opening is smaller doesn't mean the picture will come out darker in the end.
Basics: exposure (the sum of light hitting the sensor) is determined by the two components shutter speed and aperture opening, both regulating the amount of light that the sensor is exposed to during one particular exposure.
Lets introduce the term exposure value (EV). A particular scene calls for EV 12 for it to come out properly exposed. EV 12 means a shutter time of 1/125 sec combined with an aperture opening of 5,6. BUT the same exposure (EV 12) will be the end result it we double the shutter time to 1/60 sec and reduce the aperture opening one step to 8. So, the same end exposure (EV) can be obtained by a number of combinations of shutter speed and aperture.
Conclusion: if one camera (phone) has a fixed aperture of 2 and another one of 2,8, it doesn't mean the one with the smaller aperture will produce darker pics. It means that camera will have to use a longer exposure time (slower shutter speed) to obtain the same exposure.
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Posted: 2008-11-06 11:37:52
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Does that mean due to smaller aperture size of K800 in comparison to c702, it ( the K800) takes 'a tad' better pic at low light conditions.
K800 have bigger aperture size (f/2.8 instead of f/3.2). remember that fully opened (biggest) aperture is f/1.0 which means max amount of light reaching the sensor
better pics at low light? no, simply because of fact that quality depends on two major things:
1. amount of light
2. sensor
you can give a lot of light on crappy sensor and results will be bad. you can also give not much of light on good sensor with fantastic results. sensor used in C702 is better for low light conditions. ISO640 picture from C702 is not bad while K800 pic suffer due to high noise
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Posted: 2008-11-06 11:54:13
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The Aperture Controls Light and Depth Of Field:
http://www.shortcourses.com/use/using1-9.html
http://www.photoaficionado.com/situationroom/aperture.html
http://www.windowsphotostory.com/Photography/Aperture.aspx
Q: why f/2.8 and not something near f/1.0 to catch more light?
A: because of very narrow depth of field effect. bigger aperture is good compromise
there's also another crucial aspect of various aperture sizes: shutter speed
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Posted: 2008-11-06 12:09:03
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Understanding Focal Lengths:
http://www.shortcourses.com/use/using5-2.html
remember to watch animations! they are the best examples
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Posted: 2008-11-06 12:16:13
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So focal length and sensor size go together, i quote this
A smaller sensor penalizes you when used with shorter focal length lenses (top). Its smaller sensor captures a smaller part of the image circle (the white outline) than a camera using a full frame sensor or film so it has a longer effective focal length
A smaller sensor gives you a bonus when used with long focal length lenses or macro lenses (bottom). Its smaller image sensor captures a smaller part of the image circle (the white outline), increasing magnification.
So the c702 must be using a bigger sensor to go with it's smaller focal length, probley why my pics are more detailed with the c702 than they were with my k800, bigger sensor so less noise reduction is needed.
The k800's bigger focal length of 5.2mm is made to go with it's smaller sensor, and the c702's smaller focal length of 4.2mm is made to go with it's bigger sensor.
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Posted: 2008-11-06 13:00:16
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Are we all missing the point here? The question is what is the better lens, the lens with lower aperture is almost always better, period. Yeah you van lengthen shutter speeds etc but a lower aperture lets you take more "real" pictures with faster shutter and without flash, that's why F/0.5 lenses cost thousands of dollars, and yes they have a completely different field of focus, but that's a good thing.
f/1 with no flash in a dark church, yet no need for a camera mount! Plus the pic looks "professional" due to the background blurring. A lower aperture on a lens is always better.
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Posted: 2008-11-07 07:47:44
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There was just so much wrongness in this thread I had to register on Esato to put some *facts* into it.
The text on the phones can be slightly misleading, because there is no standard way to write focal length and f number (aperture).
Focal length (in mm) is a property of the lens - in itself it tells you nothing about quality. The angle of view (what ppl call wide-angle or telephoto) - is dependent on the focal length *and* the sensor size. 4.2mm on a camera phone (with a small sensor), might be equivalent to 50mm on a SLR for example.
The aperture (in f/ stops) is the ratio of the maximum diameter of the 'optical hole' in the lens to the focal length. Hence the 1:2.8 or 1:3.2, often abbreviated to f/2.8 or f/3.2 or even just f2.8, f3.2, the ratio '1:' is left off because it is implied
A wider aperture is a *smaller* number, and all things being equal a wider aperture lets in more light. Thus an f/2.8 lens lets in twice as much light as a f/4.0 lens (as the aperture is a ratio of the diameter, the doubling or halving of light intensity goes by the sqrt(2)=1.41 => 2.8 *sqrt(2) = 4.0 ). This is irrespective of focal length. As the f/ number is decreased the depth of field is decreased, the amount of light transmitted is increased and the number of abberations (bad things) increases, so for wide aperture (low f/ number) lenses the complexity (=> cost) increases. f/2.8 lenses are easy to make (since the past 100 years, e.g. the Cooke Triplet and Tessar 4 element designs). SLR camera lenses normally have a variable aperture - you can make the hole smaller in increase the depth of field. I guess that cam phones have a fixed aperture and only vary ISO and shutter speed to achieve correct exposure
So the K810 with a f/2.8 lens lets in approximately 1.5x as much light as the c702 (f/3.2) lens. Therefore the shutter speed can be 1.5x faster for the same exposure => less motion blur in low light conditions. When there is plenty of light (outdoors) then there is no practical difference. But the actual size of the sensor is not known (to me) - so I don't know which lens has the wider angle of view (the 5.2mm on the K810 or the 4.2 on the C702), notice how the focal length is not relevant for exposure!
[ This Message was edited by: Azathoth on 2008-12-14 22:47 ]
[ This Message was edited by: Azathoth on 2008-12-14 22:49 ]
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Posted: 2008-12-14 23:43:52
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Lightspeed_x Posts: > 500
Thank you all for the explanation, i've bookmarked this thread so i can read it every once in a while....
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Posted: 2009-02-18 16:59:14
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