what's so impt abt lens size?


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shuy

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#1
there r so many different diameter sizes for lens, i'm wondering what's the significance behind it all? bigger = better?
 

shidenx

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#2
Actually it is important to get the correct diameter for watever lens u have. IF its not the same it will not fit your camera's thread. Thats all.
 

iceman

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huh?? i thought the mount for a particular brand of camera would be the same - mount for eg d30 and d60 and 10d are similar.

my understanding - lower f stop would mean bigger diameter.
 

shidenx

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He's asking about the diameter of lenses. Not mount Size. how can a 58mm uv filter fit a thread size smaller or larger than that of 58mm
 

munfai

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generally the larger the diameter, the larger the front element and thus larger the maximum aperture as more light is can be captured.

general exceptions are fisheyes and wide-angles, as they need a large front element for a wider angle of view. but these lenses don't come cheap as well... :(

you can say that bigger = more expensive. not necessarily better.
 

Andy Ho

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I think you guys are very confused about what you are talking about. Please note that generally when lens diameter is being referred to, it meant the front diameter of the lens.

For certain lenses, especially zoom lenses with many glass elements, it is of paramount importance to calculate the exact angle that light will travel within the lens to hit the film precisely where it should be hitting. Part of the calculations demand that the front lens diameter be big so as to "compensate" for the angle that the light will need to move thru the many lens elements inside.

The other reason is that by allowing a bigger diameter on the front, more light is let in so as to counteract vignetting. Vignetting is a darkening of the edges caused by not having light hit the film surface uniformly from centre outwards to the edge of the film. It is especially prominent with lenses that has big aperture to begin with, eg: f/2.8.....and coupled with long lens body.

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iceman

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#7
Originally posted by shidenx
He's asking about the diameter of lenses. Not mount Size. how can a 58mm uv filter fit a thread size smaller or larger than that of 58mm
well, thats what i thought and i don't think your post mentioned filter at all.

that's why i mentioned about f stop which would relate to aperture.
 

shidenx

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Erm i mention fitting the camera's thread not mount. Hehe oh nvm he's talking about filter size of the lens! There no more confusion
 

shuy

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my 3100Z has a lens size of 46mm only, but it's wide enuff to allow a aperture of 2, n it doesn't have any vignetting, at least to my untrained eye. so y r there lens that r sooo much bigger? has it got to do wif zoom capability? i.e more zoom = longer focal length = wider lens needed? wild guess...
 

Larry

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#10
Originally posted by shuy
my 3100Z has a lens size of 46mm only, but it's wide enuff to allow a aperture of 2, n it doesn't have any vignetting, at least to my untrained eye. so y r there lens that r sooo much bigger? has it got to do wif zoom capability? i.e more zoom = longer focal length = wider lens needed? wild guess...
nope, it's to do with aperture size. generally the bigger the aperture range (e.g. f/2.8 and bigger), the bigger the lens element. that's why you can have a massive 70-200 f/2.8 while the f/4.0 version is so much smaller.

the lens size on the 3100z is much smaller cos simply put, the sensor is so much smaller than say the 35mm standard. it also means that the f/2 aperture on the 3100z allows in the same amount of light that a f/2.0 lens delivers to a 35mm camera, relative to the size of the film/sensor. meaning, smaller sensor needs less light, bigger sensor needs more light.

of course the absolute size of the apertures and sensors/film directly affects the DoF, which means the smaller sensor of the 3100z will give more depth-of-field. but that's another confusing matter altogether.

hope that helps... :D
 

shuy

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#11
Originally posted by Larry
nope, it's to do with aperture size. generally the bigger the aperture range (e.g. f/2.8 and bigger), the bigger the lens element. that's why you can have a massive 70-200 f/2.8 while the f/4.0 version is so much smaller.

the lens size on the 3100z is much smaller cos simply put, the sensor is so much smaller than say the 35mm standard. it also means that the f/2 aperture on the 3100z allows in the same amount of light that a f/2.0 lens delivers to a 35mm camera, relative to the size of the film/sensor. meaning, smaller sensor needs less light, bigger sensor needs more light.

of course the absolute size of the apertures and sensors/film directly affects the DoF, which means the smaller sensor of the 3100z will give more depth-of-field. but that's another confusing matter altogether.

hope that helps... :D
by sensor do u mean the CCD? so cos my 3100Z has a 3.34MP CCD, it doesn't need so much light? does this mean the size of the lens should correspond to the size of film/CCD? there r so many lens sizes, but how many film sizes r there? hmm... i'm still not understanding something.... :dunno:
 

SianZronG

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#12
the sensor size of your 3100z is only 7.18 x 5.32 mm

while the D30/D60/D10's sensor size is 22.7 mm x 15.1 mm

see the difference in sensor size and lense size? :D

It's about 3 times bigger. and close to the 35mm film format.

that's why it's much much much much much much more advanced sharper / cleaner / noisless than the normal consumer CCD/CMOS
 

shuy

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#13
so size does matter eh? :)

so the bigger the sensor, the better the quality of the pic?

does sensor size correspond to MP size in any way?

the fuji S304 has a bigger lens size than mine, tho the MP is the same. does that necessarily mean it has a bigger sensor n therefore better picture quality? the other main diff. between them is that mine is 3X zoom, while the 304 is 6X.
 

SianZronG

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#15
Originally posted by shuy
so size does matter eh? :)

so the bigger the sensor, the better the quality of the pic?

does sensor size correspond to MP size in any way?

the fuji S304 has a bigger lens size than mine, tho the MP is the same. does that necessarily mean it has a bigger sensor n therefore better picture quality? the other main diff. between them is that mine is 3X zoom, while the 304 is 6X.
it has a bigger lense size cause more distance is required from the CCD to the lense acuse of the higher zoom. you need more distance so more magnification. so small camerea usually don't have much zoom.
 

SianZronG

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#16
Originally posted by shuy
so size does matter eh? :)

so the bigger the sensor, the better the quality of the pic?

does sensor size correspond to MP size in any way?

the fuji S304 has a bigger lens size than mine, tho the MP is the same. does that necessarily mean it has a bigger sensor n therefore better picture quality? the other main diff. between them is that mine is 3X zoom, while the 304 is 6X.
it has a bigger lense size cause more distance is required from the CCD to the lense acuse of the higher zoom. you need more distance so more magnification. so small camerea usually don't have much zoom.

for example the C-4000z VS C-730uz same design one 10x Zoom one 3x Zoom the C730uz has a huge barrel compare to the C-4000z. :D
 

Ian

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#17
Originally posted by Andy Ho
For certain lenses, especially zoom lenses with many glass elements, it is of paramount importance to calculate the exact angle that light will travel within the lens to hit the film precisely where it should be hitting. Part of the calculations demand that the front lens diameter be big so as to "compensate" for the angle that the light will need to move thru the many lens elements inside.
More confusion it seems :devil:

The angles of refraction (bending) are determined by the refractive properties (denstiy) of the glasses used in the individual lens elements and their curvature, focal length and other optical properties. Couple this with the general optical design of a lens (it varies) and the front element size relative to the image circle becomes largely irrelevant. However, where the size of the front element is important is in determining the effective maximium aperture of the lens based on the size of the lens diaphram (field stop) which is in most cases a mechanial limitation imposed by the camera lens mount.

Originally posted by Andy Ho
The other reason is that by allowing a bigger diameter on the front, more light is let in so as to counteract vignetting. Vignetting is a darkening of the edges caused by not having light hit the film surface uniformly from centre outwards to the edge of the film. It is especially prominent with lenses that has big aperture to begin with, eg: f/2.8.....and coupled with long lens body.
It seems the others aren't the only ones who are confused :)

What you refer to is correctly termed Mechanical Vignetting and its sole cause is mechanical obstructions in the lens design, these can include such things as the aperture diaphram and control, mechanical components in the lens and the design of the lens body itself.

While it is true that using a larger front and or rear element can assist in reducing mechanical vignetting it's not always a desirable solution due to massively increased costs and weight of the finished lens.

A darkening of the edges is actually caused by uneven illiumination rather than vignetting or mechanical vignetting which causes a black region where there is NO light transmitted as it is blocked.

Uneven edge illumination is termed 'natural vignetting' and is an extremely complex optical process that requries some pages of mathematics to explain and frankly is of no interest to the readers here. However in simple terms it occurs due to the optical design being used, the size of the image circle projected by the lens and about a dozen other complex factors.
 

shuy

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#18
Originally posted by SianZronG
it has a bigger lense size cause more distance is required from the CCD to the lense acuse of the higher zoom. you need more distance so more magnification. so small camerea usually don't have much zoom.

for example the C-4000z VS C-730uz same design one 10x Zoom one 3x Zoom the C730uz has a huge barrel compare to the C-4000z. :D
so is the sensor bigger in C730 than C4000? or is it the same size? any difference in quality?
 

SianZronG

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#19
Originally posted by shuy
so is the sensor bigger in C730 than C4000? or is it the same size? any difference in quality?
same sized CCD. but to get higher Zoom ratio the lense must have a bigger construction to allow in more light .
 

denizenx

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#20
Originally posted by SianZronG
same sized CCD. but to get higher Zoom ratio the lense must have a bigger construction to allow in more light .
no it's just to fit in more elements -- it's longer not wider...
notice the lumix 12x has a wider but similar length, gives horrible CA...

lol this is the best thread yet... fun fun fun
 

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