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12

The fundamental driver of cost in a lens is not the correction of aberrations, although the correction of aberrations does add to the cost of a lens, and may be a more significant factor in wider angle lenses. Generally speaking, the primary cost of a lens is the "glass". I put glass in quotes, because sometimes it is other materials, such as Fluorite or a ...


12

There is a clear difference in intent and design philosophy. The Canon 50 f/1.2L is a bokeh machine, offering not only shallower depth of field (due to the ultra wide f/1.2 aperture) but also a smoother background blur on account of the decision to leave a certain amount of spherical aberration in the design. It's a lens with character and a distinct look, ...


9

A Flair for flare. Flare reduces the contrast of the image captured. It can affect the image overall or selectively. I'm going to make a great leap of faith and guess that you are after selective flare such as a round or symmetrical shape that plays across the image. Your concept of what is beautiful and desirable versus undesirable is personal and will ...


9

Distortion caused by a lens's optics would give you barrel distortion (objects appear to bulge outward) or pincushion distortion (squishing inward). The skewed lines you are observing are straight; this is perspective distortion, and is not a problem caused by the lens nor fixable with better optics (you can fix it with a tilt-shift lens, but that's a ...


8

This not a thing that can happen. Cameras just don't work that way. For that matter, light doesn't work that way. Specifically, for digital cameras: every "photosite" — each individual pixel-level sensor — is just a counter of photons. It doesn't have any sense of the wavelength of the light received, and correspondingly no perception of color. In order to ...


7

OK i will try to actually answer this! there is a distinction between HAZE and flare - for the purposes of this I will cover FLARE only. Lens flare is caused by light from a particularly bright source such as the sun or a bulb directly striking the lens element surfaceS at an off-centre axis, and not being REFRACTED but instead being REFLECTED either off ...


6

You can find a lot of others with this problem, especially some Nikon primes. Apparently, also zooms like yours. It is reflection from the glass in front of the sensor that reflects back to the lens rear element. The colour and power of the spot depends on camera/lens combination, but often it is reddish (pink, magenta, whatever you want to call it) ...


6

Cost and ease of design. The main purpose of mirror telephoto lenses is to make them much more cheaply and compact than a conventional refractive lens can be produced. This is easiest to accomplish by coating the back side of a negative meniscus lens (known as a Mangin mirror) instead of creating a parabolic first surface mirror that would need to be shaped ...


6

Using the EXIF data, you should be able to use the following formula: (Resolution in pixels/Focal plane resolution in dpi) X 25.4(mm/in)=size in mm For my Canon 5DII, the horizintal and vertical numbers figure out to: (5616p/3849.21ppi) X 25.4mm/in = 37.058mm (3744p/3908.14ppi) X 25.4mm/in = 24.33mm Once you have the horizontal and vertical measurements, ...


6

You're getting what is called Perspective distortion which is most noticable in wide angle lenses. Check out this link for more info: http://en.wikipedia.org/wiki/Perspective_distortion_(photography) Basically close up objects in the center of the frame will look enlarged while objects on the sides will be stretched away from the center of the photo.


5

Two reasons: A camera objective (made up from many lenses) needs to focus on a plane, not an arc. And we dont see the image projected on the back of our eye ball. We build up the image from features extracted by many neurons with each their specialty. That's why we don't have to show reality to the eyes for us to see the same, we just need to construct ...


4

The lower the number after the F, the more light gets into the camera. More light means - you can get away with shorter exposure times. - you have lower depth-of-field (which is a good thing in portrait shots) The ranges given for the lenses are the values for the wide angle and the tele setting of the lens. Generally you want the numbers to be as low as ...


4

A screw on diopter filter with a positive index number refracts light from a narrower angle of view before it strikes the front element of the original lens. It obviously adds another lens element to the optical path of the light reaching the film/sensor. This will affect overall image quality to one degree or another, depending upon the quality of the screw ...


4

Without knowing the focal length, the exact lens added to the front of the existing one can't be calculated. However, what you want is called a "closeup lens". These are usually single-element convex lenses that mechanically mount as filters. First you have to find the diameter of the filter mount on the lens. This is usually written on the front of the ...


4

An aperture could be closed which is effectively an infinitely large f-stop number since no light gets through. The fastest possible (smallest f number) is a bit harder. The speed of a lens is based on the ratio of the entrance pupil to the focal length of the lens. The longer the focal length, the bigger the entrance pupil must be. In theory you could ...


4

I'm out of my element here, but... I did some testing and it seems that if you take the horizontal/vertical resolution of the camera's sensor, divide that by the Focal Plane Horizontal/Vertical Resolution EXIF value, then convert the result to millimeters, you get a very close estimate to the dimensions of the sensor size. Example, using my T4i: Sensor ...


4

You've probably heard people describe some lenses as "unusably soft wide open, but passable at f/2.8 and excellent from f/4", or similar. That's because, basically, these lenses are already designed in the way you suggest, although additionally constrained by size, weight, complexity, cost, and other design factors. And they also let you use the lens at ...


4

Flare is a non-standard use case for a lens, i.e. it's outside the intended operating conditions. As such it tends to be a little bit random how a lens flares as it's a side effect of various design decisions that are made without concern for how it affects flare. I have heard many times anecdotally that older lenses that are less thoroughly corrected for ...


4

Panavision offer dedicated lenses attributed to more desirable lens flare - this all comes down to the coating and treatment of the glass: http://www.panavision.com/content/spherical-specialty Additionally, in films such as Star-Trek, Super-8 etc, they have hot lights just off camera to add glares already attributed to the on-camera light sources. Though ...


3

if I measure the size of the entrance pupil by looking at it, will that be equivalent to the focal length of the lens divided by the f-number Yes. F-number is defined in terms of focal length and entrance pupil diameter, so if you know any two of: entrance pupil diameter, f-number, and focal length, you can calculate the third number. The equation that ...


3

Simply put, it does, our brain corrects for it. Among other things, you can't actually see where your optic nerve attaches to the retina and your visual acuity is actually much more center focused than even a cheap camera lens, but because your eyes refocus on the fly every time you change where you are focusing, you don't notice the changes or the lack of ...


3

STM and USM are different kinds of focusing motors. Prior to STM, USM was the preferred option because it was fast and quiet (relative to other kinds of motors that are available). However, it isn't fluid which becomes an issue with video. Enter STM which is also quiet (though I'm not sure which is more quiet) and provides a smooth transition as it focuses ...


3

You can look at DxOMark's Lens Ratings, and particularly the Optical Metric Scores, which include a T stop measurement. I don't put too much stock in DxOMark's overall numbers (which don't have much practical impact for real use), but if you're interested in this particular thing, here's a way to tell. Manufacturers do not typically give this number, so the ...


2

The extra glass in a fast lens is not just there to correct aberrations. The full aperture must be visible across the whole field of view meaning for moderate or wide lenses, you can't just make the aperture larger you'd have to make all elements in front of the aperture much larger as well. But your idea is sort of in effect with large format lenses. Many ...


2

Physics plays a role in answering your question and that information is out there. The basics from that linked discussion are that the index of refraction of the lens material will affect the maximum aperture you can achieve, so for pure glass that has an index of refraction of 1.5, the maximum aperture would be f/0.5 or thereabouts. Better substances, such ...


2

After some reading, this is what I've found: There's no guaranteed indicator of which lenses will show focus shift, but fast primes, especially lenses optimized for smooth out-of-focus blur ('bokeh'), are the most likely to show it. Older designs or those intentionally pursuing a 'classic' appearance are particularly likely. Single aspects of lens ...


2

On a zoom lens, it's common for maximum aperture to vary from one end of the zoom range to the other. Typically, the largest aperture (smallest f-stop number) will be available at the wide end of the zoom range, and it will decrease throughout the range until it reaches the smallest maximum value (yes, it's sort of confusing) at the telephoto end of the ...



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