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Old Mar 14, 2010, 10:36 AM   #11
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Focal length has nothing to do with resolving power, you can have a sharp 50mm lens you have had a weak one. That is down to lens design and quality of materials used. So what TCav has said still stands true and this other area is a tangent to the purpose of the tread so to discuss it best I would suggest starting a new thread so this doesn't get confusing for someone using this for reference.
Quite right. Resolving power is a by product of light gathering ability. But in todays world, when we talk about these little zoom P&S cameras, it has become linked in the advertizing (and the publics mind) to FL. Which is why I call them "miniature" telephoto lenses.

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Old Mar 16, 2010, 8:28 AM   #12
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Resolving power is a by product of light gathering ability.
No. Light gathering ability is a function of pupil diameter. "Resolving power" is sharpness, and while varying the pupil diameter varies sharpness, that's because a smaller pupil diameter masks out optical flaws. And neither resolving power or light gathering ability has anything to do with focal length or crop factor.
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Old Mar 16, 2010, 1:04 PM   #13
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And neither resolving power or light gathering ability has anything to do with focal length or crop factor.
Err, this doesn't make ANY sense.

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Old Mar 16, 2010, 1:07 PM   #14
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Are you suggesting that resolving power and/or light gathering ability is in some way related to focal length and/or crop factor?
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Old Mar 16, 2010, 2:25 PM   #15
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Are you suggesting that resolving power and/or light gathering ability is in some way related to focal length and/or crop factor?
Focal lenght and aperture together are what create resolving power.

The cropping factor has no effect on resolution, but Does clarify whatever Can be resolved by the above factors.

Telescope Optics Formulas with Calculators

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Old Mar 16, 2010, 6:58 PM   #16
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Focal lenght and aperture together are what create resolving power.

The cropping factor has no effect on resolution, but Does clarify whatever Can be resolved by the above factors.

Telescope Optics Formulas with Calculators

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Dave, I think you are really reading too much in from these articles that you are linking to here and http://forums.steves-digicams.com/ne...ml#post1066192 and in a lot of cases they don't relate to the thread itself.

This thread was designed (very well I might add) by TCav to help give insight to the different sensors out there and how they effect field of view.

Most of the time what can be resolved is a non issue as it isn't the limitation of the physics but the manufacturers making the lenses. If you buy top glass then we are not reaching the limits so it is a non issue.
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Old Mar 16, 2010, 7:25 PM   #17
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Resolving power is the power of a system to resolve, or distinguish between two points. Resolving power is typically expressed in line pairs per millimeter (lppmm), or Modulation Transfer Function (MTF). There are lots of factors that can affect the resolving power of a lens, from the design of the lens through it's manufacturer and use. But the resolving power of lenses do not vary with focal length. That is, lenses with shorter focal lengths do not generally have greater resolving power than lenses with longer focal lengths, and vice versa.

The pupil diameter (aperture) doesn't affect the resolving power in any way, except that lenses that don't have a great deal of resolving power can perform better if a diaphram is closed such that, for instance, portions of the lens where the polished surfaces have more variability are prevented from contributing to the image. The same is also true of the crop factor, in that, less than perfect portions of an image are simply cropped out. These methods don't actually increase the resolving power of the optics, they just block the light where the resolving power is less than perfect.

A lens could be manufacturered that has the theoretical maximum amount of resolving power, within the limitations of light and the tools and materials being used, and its focal length and pupil diameter could be anything. Of course, a lens with a smaller pupil diameter would be easier to manufacture. And, of course, the physical size of the image sensor would have nothing to do with the resolving power of the lens.
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Old Mar 16, 2010, 7:40 PM   #18
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Resolving power is the power of a system to resolve, or distinguish between two points. Resolving power is typically expressed in line pairs per millimeter (lppmm), or Modulation Transfer Function (MTF). There are lots of factors that can affect the resolving power of a lens, from the design of the lens through it's manufacturer and use. But the resolving power of lenses do not vary with focal length. That is, lenses with shorter focal lengths do not generally have greater resolving power than lenses with longer focal lengths, and vice versa.
Resolving power, if we except your limited definition means that a 50mm lens can resolve the same amount as an 1200mm lens.

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Resolving power is the ability of the components of an imaging device to measure the angular separation of the points in an object. The term resolution or minimum resolvable distance is the minimum distance between distinguishable objects in an image, although the term is loosely used by many users of microscopes and telescopes to describe resolving power. In scientific analysis the term "resolution" is generally used to describe the precision with which any instrument measures and records (in an image or spectrum) any variable in the specimen or sample under study.
This can only be accomplished by a combination of the light gathering ability and focal length. Other wise we are left in the ludicrous position of saying that a good 50mm lens can out resolve a bad 1200mm lens at 200 yards. Mind you, focal length, in and of itself, is a meaningless number (no argument). There is a formula in one of the links I posted for determining resolving power.

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Old Mar 16, 2010, 7:40 PM   #19
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Dave, I think you are really reading too much in from these articles that you are linking to here and http://forums.steves-digicams.com/ne...ml#post1066192 and in a lot of cases they don't relate to the thread itself.

This thread was designed (very well I might add) by TCav to help give insight to the different sensors out there and how they effect field of view.

Most of the time what can be resolved is a non issue as it isn't the limitation of the physics but the manufacturers making the lenses. If you buy top glass then we are not reaching the limits so it is a non issue.
My bad - This is my last post.

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Old Mar 16, 2010, 9:09 PM   #20
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Resolving power, if we except your limited definition means that a 50mm lens can resolve the same amount as an 1200mm lens.
Within their respective angles of view, absolutely. What were you thinking?

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This can only be accomplished by a combination of the light gathering ability and focal length.
Light gathering ability is a function of focal length and pupil diameter. The aperture (expressed as an f-number) is a function of just those two values (f-number = focal length / pupil diameter.) All f/2.8 lenses have the same light gathering ability regardless of their focal length or the crop factor of the body they're mounted on.
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