It's a bird

by Vian Esterhuizen

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0

Of course you could always reverse engineer the lens housing completely, first place it in an X-ray machine at different angles to determine the spacing, possible movements, builtin mechanisms etc. Then take it apart physically to inspect the lenses, you can then determine the shape of each lens and its properties. You can also inspect other objects. If you ...


0

With larger mount you can have larger exit pupil diameters. Ratio of entrance pupil and exit pupil is a measure for a lens symmetry. So with larger mount I suppose you can achieve more symmetric designs. The level of asymmetry affects among else depth of field (at given focal length, distance and aperture) and depth of focus. The look of out of focus ...


2

The mount's throat diameter limits the exit pupil diameter. It also has strong control over vignetting, so it restricts the pursuit of ultra-large aperture lenses with acceptable light falloff.


22

In general there are no secrets to lens design. Everything important, all breakthroughs, etc., are shared publicly or semi-privately with modification through patents, conferences, papers, etc. There are "temporary secrets" where something is closely guarded until it is published: For example, we have completed the final piece of the puzzle in free-form ...


1

Smaller format lenses are eased by having lower maximum image heights and smaller fields of view at the same focal length. Each aberration has explicit field dependencies which describe the rate at which they grow. For the following equations, y is the ray height at the lens and h is image height. Spherical Aberration varies by y3. Coma varies by y2h. ...


1

For Canon, the EF-S was designed to precicely scale down the geometry of EF by the crop factor. SO, the EF-S 17-55 f/2.8 gets its design kick-started by shrinking down the existing design for ... well, they don't make a EF 27-88, so not the clearest example. But I have read that some designs are scaled down. IAC, the rather large 17-55 is 1.6× smaller ...


2

A lens that is truly telecentric in image space necessarily has no focus breathing. That is to say, the chief ray is parallel to the optical axis between the rear element and the image plane. Here is an image from thorlabs: To locate the chief ray, look for the ray bundle beginning from the furthest object point or angle from the optical axis. The ...


4

Cine lenses are designed to minimise focus breathing so that directors can perform large focus pulls quickly without viewers becoming disoriented by the field of view changing. However you can expect to pay five figures for a genuine cine lens (don't be fooled by Samyang/SLRmagic etc. "cine" lenses, they are just DSLR designs with stepless apertures and ...


7

If you are looking for a macro lens that does not noticeably breathe, the best one that I know of is the $1800 Zeiss 100mm f/2 Makro-Planar. The Canon 100L and non-L are both quite bad for this, and the Nikkor is worse. I am not sure about the Tamron non-VC or the Sigma, Tokina, etc., lenses. The Zeiss 100/2 only provides 1:2 magnification so you will ...


1

Aperture is a bit of a misnomer; a hold-over from simpler times and simpler lens designs. What matters is the entrance pupil, or the apparent size of the aperture as viewed through the front (business end) of the lens. With a simple lens design (a double-Gauss or Tessar, for instance), the physical aperture and the entrance pupil are approximately the same ...


-2

Fixed maximum aperture lenses don't really have any advantage, and they never did. If you want an aperture that you can maintain throughout the entire zoom range you can just select one that is available at all zoom settings. An f/3.5-f/5.6 lens will stay at 5.6 no matter how much you zoom. Fixed maximum aperture basically come in two variations; High ...


0

Assuming a "medium" brightness (averaging day & night), ISO 25, f/64, with a 9-stop ND should get you to about 30 days. I haven't seen a reciprocity failure chart that goes that high, but I would assume that would carry you out as far as you want to go. A lot of assumptions, but it sounds possible to me.


0

As @BobT suggests, a sharp lens with neutral-density filter(s) could do the job, or you might use multiple short exposures. In any case, take into account reciprocity failure, which will; require yet longer exposures in very dim lighting, and which causes color shifts on most emulsions. It should be interesting to see the photos here, showing only really ...


0

There are basically two ways to make a pinhole camera sharper. as Olin Lathrop said, the smaller the pinhole the sharper the image, but if it gets too small, diffraction come into play. There is an optimal diameter of the pinhole and this formula calculates it: Diameter = Constant x sqrt(Focal Length x Wavelength of light) There is a bit of mess about what ...


1

No, there is no lens design that allows for sharpening a pinhole image. This is because pinhole cameras by definition don't have lenses. You can replace the pinhole with a lens to get more sharpness with lower f-stops. That's why normal cameras have lenses instead of pinholes. With a pinhole, the sharpness gets better as the pinhole gets smaller, which ...


2

I think there are two very basic reasons why DoF scales are no longer put on lenses: zoom and autofocus. Zoom lenses would have to have dynamic DoF scales that would change for whatever focal length is set on the lens. While maybe this could be done with, say, eink or lcd displays, it's something that's never really been put on lenses before. But the more ...


3

First, a word about what depth-of-field is and is not: In a way, depth-of-field is an illusion. There is only one plane of focus. Everything in front of or behind the point of focus is out of focus to one degree or another. What we call DoF is the area where things look, to our eyes, like they are in focus. This is based on the ability of the ...


4

Not including a DOF scale can make the lens barrel smaller and allows the use of different focusing mechanisms such as linear motors instead of the traditional helicoid (which is where the DOF scale used to be printed). It is less important to have the scale as you can get instant feedback on what is and isn't in focus with a digital camera, and differences ...


0

From what I have read and and seen about aspherical lenses, they are designed to prevent aberration of light hitting the surface of the lens. This means, it prevents image distortion for the person wearing the lenses. This is accomplished by making the edges of the lens curve out, away from the curve of the spherical design of the lens, making it a sphere in ...



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