what's so impt abt lens size?
- Thread starter shuy
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I do doubt about the saying of bigger lens size sharpen the images or whatever because old days lens sizes are much smaller than nowadays. So if what you guys said are exactly to the point, then in future, the lens would be all standard minimum bazooka or what?? 
Anyway, I am no expert in this discussion. Just find it interesting suddenly there's this bigger and smaller thing..
cheers
Anyway, I am no expert in this discussion. Just find it interesting suddenly there's this bigger and smaller thing..
cheers
Originally posted by shorty
I do doubt about the saying of bigger lens size sharpen the images or whatever because old days lens sizes are much smaller than nowadays. So if what you guys said are exactly to the point, then in future, the lens would be all standard minimum bazooka or what??
cheers
Image sharpness is dependent on a number of factors including but not limited to:
Optical design of the lens.
Camera movement while the shutter is open.
Quality of the optical components.
Manufacturing tolerances of mechanical components.
Atmospheric conditions.
Thermal (eddy) currents inside the lens body.
Differing coefficients of expansion in the various lens elements.
And the following apply only to film cameras:
Acceptable circle of confusion
Film flatness relative to the film plane.
Limiting resolution of the film (grain size/structure etc).
Resolution of the developing process
The following apply to digital cameras.
Resolution of the CCD.
Equivalent acceptable circle of confusion
The following apply to photographic prints of all types:
Limiting resolution of the paper (if it's a conventional film print).
Acceptable circle of confusion.
Limiting resolution of the enlarger lens.
Print head type and resolution (for digital inkjet prints and plotter prints)
There's a lot more limting factors but those above will give you an idea of the complexities involved.
Bollocks!
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In purely optical terms the diameter of the front element of a lens is equal to the focal length of the lens divided by the size of the aperture stop at it's largest (its fixed in most optical systems, unless a variable aperture is employed like in most SLR lenses. This is an optical constant, however it can be partially circumvented with camera lenses by a variety of means including the use of image scale to allow shorter lenses of a given focal length.
hmm, though i hardly understand wat u've said (camera noob here) i don't see lens size as a direct factor. so can i take it that the lens size is dependent on the design and features of the camera, and bigger = better not cos of the lens itself but cos better features require a bigger lens?
which means if i somehow yank out my old 46mm lens n replace it wif a 100mm lens or something, it'll be the same? assuming that the big lens has the same properties as the small lens
More on the features of the lens, remember that most SLR's and better use removable lenses. However you're on the right track otherwise. Bigger glass diameters doesn't always make for a better lens.
If the optical properties were the same then there'd be no real difference on film or CCD. Also we are taling diameter of the lens, not focal length
One thing has to be remembered, In the history of camera manufacturing there have been *very* few lenses brought out that were absolutely designed as no compromise designs. The few lenses that have been made this way tend to be horrifically expensive, large and very heavy.
Manufacturers build their lenses to a price to remain competitive and to capture market share. If this means sacrificing some optical qualities or other cost cutting measures then it will be done.
In time as you learn more you'll appreciate the statements above more and more.
I think:
1. diameter of front depends on max aperture and FOV-vignetting
2. length depends on number of elements
3. mid-barrel depends on more, eg IS motor etc..
dun think quality has anything to do with size *directly*
is this enough without going into full-blown techie bits?
1. diameter of front depends on max aperture and FOV-vignetting
2. length depends on number of elements
3. mid-barrel depends on more, eg IS motor etc..
dun think quality has anything to do with size *directly*
is this enough without going into full-blown techie bits?
As a guide, do not buy lenses that are using filter larger than all other manufacturer are offering. Usually this is just a lame workaround to solve some other problem. However, if you use CPL, it is going to burn a hole in your pocket. Also, when your filter gets larger, your lens get bigger, heavier and ocuppy more space in your bag.
Take for example,
Manufacturer A can make a 19-35mm lens without Vignetting with a CPL filter and using only 62mm filter.
However, Manufacturer B cannot do so without having vignetting. To get into the market, he have to make the front cap of the lens larger and use a 77mm filter thread instead !!!!! :devil:
Take another example
If Manufacture A use 77mm filter to produce a 28-70mm f2.8 mm lens.
Manufacture B use 77mm filter to produce a 24-100 f2.8 mm lens.
It is ok, since this is probably the smallest filter size required for lenses belonging to this class.
However, if someone else come out with a 82mm filter for 24-70 mm lens. Most likely, he's not able to tackle the 24mm without having vignetting problem. :bsmilie:
Take for example,
Manufacturer A can make a 19-35mm lens without Vignetting with a CPL filter and using only 62mm filter.
However, Manufacturer B cannot do so without having vignetting. To get into the market, he have to make the front cap of the lens larger and use a 77mm filter thread instead !!!!! :devil:
Take another example
If Manufacture A use 77mm filter to produce a 28-70mm f2.8 mm lens.
Manufacture B use 77mm filter to produce a 24-100 f2.8 mm lens.
It is ok, since this is probably the smallest filter size required for lenses belonging to this class.
However, if someone else come out with a 82mm filter for 24-70 mm lens. Most likely, he's not able to tackle the 24mm without having vignetting problem. :bsmilie:
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