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K800-C702 LENS Difference |
number1
Joined: Sep 12, 2007
Posts: > 500
From: UK,kent,Sittingbourne
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Would explain, why my c702 1/5 iso640 pics are a tad darker than my old k800i 1/5 iso 640 pics, but i'm sure the smaller focal length would mean more light, the aperture on the c702 is controlled by that little black regtangle frame around the lens.
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Bialynia
Joined: Jun 13, 2008
Posts: 337
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On 2008-11-04 18:16:03, bishshoy007 wrote:
Yes number1, you are right. I now know that smaller the focal length, there are provisions for more incoming light. At wikipedia every terms are shown like this f/5 or f/3. But none of these notations are there in the tags of both the phones. I suppose then the must be f/4.2 for C702 and f/5.2 for the K800.
Then again what avout the ratios. 1/x.x
The k800i aperture is f2.8, don't worry about focal lengths when comparing the c702 and k800i since it makes no sense to, 5.8mm is the lens size for the k800i, the real issue is the aperture, f/2.8 is OK, it's about as good as you're going to get on a lens that small, the c702's is f/3.2 which is now getting into crappy territory when it comes to light but which should be expected when we see that it has a significantly smaller lens size. The C905 has a 5.91mm lens with a f/2.8, like the k800i. So long story short the K800i has the better lens over the c702. |
Raiderski
Joined: Jul 03, 2006
Posts: > 500
From: Poland, Hell, Mountains
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both values are not really important if we are not talking about anything else better than camphone. earlier I forgot to mention that depth of field (DOF) is also dependent on aperture size
Would explain, why my c702 1/5 iso640 pics are a tad darker than my old k800i 1/5 iso 640 pics
it's quite easy to explain:
fully opened aperture = f/1.0
K800 = f/2.8
C702 = f/3.2
the aperture on the c702 is controlled by that little black regtangle frame around the lens.
this may be true until 'controlled' equals 'constant'
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bishshoy007
Joined: Dec 11, 2007
Posts: 146
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On 2008-11-04 20:33:43, Raiderski wrote:
Would explain, why my c702 1/5 iso640 pics are a tad darker than my old k800i 1/5 iso 640 pics
it's quite easy to explain:
fully opened aperture = f/1.0
K800 = f/2.8
C702 = f/3.2
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. |
bishshoy007
Joined: Dec 11, 2007
Posts: 146
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On 2008-11-04 19:26:54, Bialynia wrote:
The k800i aperture is f2.8, don't worry about focal lengths when comparing the c702 and k800i since it makes no sense to, 5.8mm is the lens size for the k800i, the real issue is the aperture, f/2.8 is OK, it's about as good as you're going to get on a lens that small, the c702's is f/3.2 which is now getting into crappy territory when it comes to light but which should be expected when we see that it has a significantly smaller lens size. The C905 has a 5.91mm lens with a f/2.8, like the k800i. So long story short the K800i has the better lens over the c702.
Can you verify this with some pics. |
bishshoy007
Joined: Dec 11, 2007
Posts: 146
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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 ] |
hansen
Joined: Aug 23, 2006
Posts: 209
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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. |
Raiderski
Joined: Jul 03, 2006
Posts: > 500
From: Poland, Hell, Mountains
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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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Raiderski
Joined: Jul 03, 2006
Posts: > 500
From: Poland, Hell, Mountains
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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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Raiderski
Joined: Jul 03, 2006
Posts: > 500
From: Poland, Hell, Mountains
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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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number1
Joined: Sep 12, 2007
Posts: > 500
From: UK,kent,Sittingbourne
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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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Bialynia
Joined: Jun 13, 2008
Posts: 337
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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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Azathoth
Joined: Dec 14, 2008
Posts: 1
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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 ] |
Lightspeed_x
Joined: Mar 03, 2008
Posts: > 500
From: Dominican Republic
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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: 2008-11-04 19:10
