18

Your observations of the lens leads you to both a correct, and incorrect, conclusion. Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 ...


8

They are two totally different designs. One is a non-extending lens that does all of the "zooming" internally. The other is an extending zoom lens that is considerably shorter at 70mm than at 200mm. In fact, the RF 70-200mm f/2.8 L IS is slightly longer than the EF 70-200mm f/2.8 L IS III when the RF lens is zoomed all the way in to 200mm.


7

A lens cap or cover is hardly necessary. Minor scratches won't really affect your image quality (LensRentals 1 & 2). What a lens cap does do is protect the lens in transit so that you can instantly take a shot - no accidental finger prints or dirt smudged while en route. That being said, the lens appears to be recessed, making the accidental finger ...


6

You need to differentiate the camera, on where the sensor or film resides and the optical elements. This can be either lenses or mirrors. A mirror telescope is a good example of an open structure. This structure is only to hold the elements aligned. But it still needs housing at the end, to make a labyrinth so no direct light enters the last element, where ...


6

I am not sure about other manufacturers, but Canon uses a "secondary diaphragm" in some of their constant aperture wide and standard zooms. Here is a lens grouping Block Diagram depicting the secondary diaphragm in front of the primary diaphragm. Here is a video that shows it in operation as you zoom the lens: EF 24-105mm f/4 Secondary Diaphragm


5

Lenses with very narrow angles of view require front elements that are roughly equivalent to the size of the entrance pupil. A typical telephoto prime lens will have a front element less than 10% larger than the entrance pupil at the lens' maximum aperture. This is because the light rays collected by the lens are almost perpendicular to the imaging plane and ...


5

Why is zoom provided in Tokina 11-16mm? Tokina has specialized in zooms. The reputation of their AT-X lenses is basically built upon their acquisition of highly-regarded zoom technology from Angénieux. Their current lens lineup includes: Six primes: 20mm x2, 50mm, 100mm x2, 300mm. Fifteen zooms. Like their primes, many of their zooms duplicate the same ...


5

Camera lenses are converging lenses, meaning they have positive power. A simple convex lens will do this job, however, the image is flawed. I am talking chromatic aberration whereby each color will come to a focus at a different distance downstream of the lens. Now a negative lens diverges and a positive lens converges. Additionally they display opposite ...


4

The point is versatility, so one can change from 11mm to 16mm or anywhere in between as needed, and not be restricted to just 11mm. I compose my shots so no cropping is required, unless something prevents me from doing so. I may prefer to have a zoom or two instead of a camera bag full of 20 different prime lenses. I do not see "fixing it in post ...


4

In its current design, it was achieved by using an extending lens body. A recent interview in DPReview with Canon's executives states: Q: In terms of making the new 70-200mm smaller, how difficult was it to decide to move to an extending zoom design? A: We've not actually disclosed that it is going to extend or not, but we do have the extending ...


3

Of the four Canon zooms I have within arms reach at the moment: I had already noticed it in the EF 24-105mm f/4 L IS a long time ago. I do not see it at all in the EF 70-200mm f/2.8 L IS II nor the EF 24-70mm f/2.8 L. There may be just a bit of it happening in the EF 17-40mm f/4 L. The strong negative magnification between the front element and diaphragm ...


3

That all depends upon what information the lens diagram in question offers. Other diagrams from other sources often show information not included in your example. They may show things such as the location of IS elements, aperture and secondary aperture locations, floating elements, focusing elements, etc. Consider this Canon published block diagram for the ...


3

There's not really any standard for what "better" or "not better' color is. There are only more saturated or less saturated colors, and colors with a cast or tint in one direction or another around the color wheel. What one considers "better" or not is strictly an individual opinion. There are standards for capturing and displaying accurate color, but that ...


3

With respect to color, better is often a matter of opinion. Different wavelengths may be transmitted differently depending on lens element materials and coatings. This is most noticeable when comparing very old lenses with modern lenses. They are usually most noticeable as warmer or cooler colors when white balance is set to auto (on some cameras). However, ...


3

This is easier to understand when we consider what made professional lenses during that time period more expensive. While a dozen criteria (like optical design, lens coating, and weather sealing) contribute a little to the cost, production costs and quality thresholds have the most impact. Production costs Consumer grade "lowest tier" lenses could be ...


2

I don't know if anyone still cares about this, but you can get very short focal length mirror lenses. Schwarzschild microscope objectives use mirrors. They might have focal lengths ~0.5-5mm. These are highly corrected for microscopic work, not for conventional photography. As others have mentioned, mirror lenses have a central obstruction, this would ...


2

Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, ...


2

I agree with user86418's assessment that Jerry Coffin's answer has this backward, though he in turn seems to have conflated numerical aperture with ƒ/number. Quoting outdoorphotographer.com In a variable-aperture zoom ... elements in front of and behind the diaphragm move (and the diaphragm itself moves), so the entrance pupil doesn’t vary in ...


2

You're confusing diffraction limited aperture (DLA), which is where the effects of diffraction are first barely detectable using a specific digital sensor, with the diffraction cutoff frequency, which is reached at a much smaller aperture. For most cameras it is much smaller than the lens' minimum aperture. For a digital camera, the DLA is determined by ...


2

I have previously disassembled and adapted one such lens – Steinheil-Munchin Cassarit 50/2.8. At all distances, it was sharpest when the front element was set to infinity and the entire lens was unit focused with a helicoid adapter. I would expect similar results with similar lenses because there aren't enough elements to correct aberrations when elements ...


2

What is the actual combination of aberrations at play here, The "spinning top" bokeh near the edges appears to be tangential astigmatism. Because the bokeh balls don't change their "width" (i.e., the diameter of the spinning top doesn't substantially change) further from the image center, the sagittal focus is fairly constant. But because the bokeh balls ...


2

As you known, the lens vignette (fall-off of the circle of good definition), is seen as a gradual dimming of an image from center to margins. The vignette has been with us always, as all lenses vignette to some degree. This is somewhat more of a problem today, as compared to the negative / negative film method employing an optical enlarger. Such a scheme ...


2

Because in many cases the flat glass needed to lengthen the back focus by the needed amount would need to be thicker than the entire registration distance. The effect of flat glass is so miniscule that it would take glass thicker than the space available to get the desired additional back focus distance for most applications. Flat glass would also ...


1

Back around eight or nine years ago I bought two bags of OP/TECH 18" rainsleeves. There are two rainsleeves in each bag. The largest lens I use them with is a 70-200mm f/2.8 with plenty of length to spare. There are other sizes available, with the "mega' size for lenses up to 25" in length. The front end of the rainsleeve has a drawstring that pulls tight ...


1

I use a rainsleeve. But in really rainy weather a long zoom isn't very usable, think of all the water between you and the target.


1

"Anthropocentric" answer: because it wouldn't be the 11-16mm zoom then, but an 11mm prime. You could just as well ask why they don't make it a 16-300. Also, 11-16 isn't this little zoom. it's nearly 1.5x.


1

Taking Rafael's answer to an astronomical extreme, in the case of gravitational lensing, where the lens element can be the sun, galaxy clusters, etc., there's no possibility of making the lens an enclosed tube. So no, a camera (more specifically, a camera's lens) does not have to have a contiguous housing.


1

Several telescope designs, some of which were used with a camera at the prime focus, were an open tube design. Such a design, under certain conditions, is favored because it is light weight. Naturally they are highly susceptible to stray light as well as differing densities of air interfering with the optical path.


1

A handy, but superficial, proxy for how much the lens will weigh and where the CG will be (although this does also depend on the density of the glass) Also depends on the size, so even if you get an idea of the scale from the size of the mount, I don't think you get enough accuracy (the weight is going to be the third power...). The CG is expected to be ...


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