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11 votes
Accepted

What can cause double-vision effect in slightly out of focus areas?

A cheap filter (uncoated or poor coatings) can reflect some of the light which is always reflected off of the front element surfaces. The primary reflection (blue in the drawing) will be stronger than ...
Steven Kersting's user avatar
6 votes
Accepted

If focal length does not affect DOF, why doesn't a 25mm lens at an f-stop of 4 give me the same DOF as a 100mm on an f-stop of 16?

Because magnification (focal length and subject distance) affects the Depth of Field more than aperture does (approx twice as much generally). Start with 50mm @ f/8 focused at 10 ft. If you halve the ...
Steven Kersting's user avatar
5 votes
Accepted

Why does viewing the sun through a telescope burn your eyes?

Assuming your eye is part of the optic system with the telescope, and assuming the exit pupil of the telescope's eyepiece isn't larger than your eye's iris (that is, your eye doesn't contribute as a ...
scottbb's user avatar
  • 32.9k
5 votes

Why has no phone manufacturer tried a lens turret system yet?

A few points why not: having such device involve sealing rotating part of phone which is not very easy and manufacturers try to minimize such details to make smooth rotation manufacturers need to add ...
Romeo Ninov's user avatar
  • 12.2k
5 votes

If focal length does not affect DOF, why doesn't a 25mm lens at an f-stop of 4 give me the same DOF as a 100mm on an f-stop of 16?

Focal length totally affects DOF. That's one of the reasons that older video camera footage and current-day cell phone video doesn't look "filmic". The sensor is tiny, so a short focal ...
Robert M.'s user avatar
  • 151
4 votes

What can cause double-vision effect in slightly out of focus areas?

The optical system consists of multiple surfaces of polished glass. Each will reflect away a small percentage of the light. Some of these reflections will hit other lens surfaces and reflect again. ...
Alan Marcus's user avatar
  • 39.3k
4 votes

If focal length does not affect DOF, why doesn't a 25mm lens at an f-stop of 4 give me the same DOF as a 100mm on an f-stop of 16?

In short: there are two reasons your expectations don't hold true: In order for crop 'equivalence' to hold true, everything must scale with crop factor, including subject distance and subject size. ...
scottbb's user avatar
  • 32.9k
4 votes

If focal length does not affect DOF, why doesn't a 25mm lens at an f-stop of 4 give me the same DOF as a 100mm on an f-stop of 16?

Circle of confusion is an absolute value. Circle of confusion can be drawn on the image itself. If you were to scale the image from 25mm lenses to match the image from 100mm you will find out that ...
Euri Pinhollow's user avatar
4 votes

Does the inverse square law apply to all lights, including light within a lens?

Light from a normal point source travels omnidirectionally, so a given number of photons(1) traveling outward from a light source must illuminate a larger sphere the further you get from the source. ...
LightBender's user avatar
  • 3,181
4 votes
Accepted

Which of these lenses to choose for a studio project?

There's really never an objective "best" choice, it all depends on what you're attempting to accomplish. My goal is to achieve the sharpest and most detailed images possible, likely ...
inkista's user avatar
  • 52.4k
3 votes

Why does viewing the sun through a telescope burn your eyes?

There is no significant difference between looking at the sun with the naked eye and taking a picture of it with a digital camera. There are only two variables that control the exposure, the duration ...
Steven Kersting's user avatar
3 votes

Why has no phone manufacturer tried a lens turret system yet?

To add to the excellent reasons already stated: modern phone cameras are a very long way from your simple "open shutter, read one frame from sensor, write data from that one frame to a JPEG file&...
Philip Kendall's user avatar
3 votes

Does the inverse square law apply to all lights, including light within a lens?

The law of the inverse square tells us that light intensity falls off 4x with each doubling of distance. In other words, if you are reading a book by the light of a single lightbulb 1 foot away from ...
Alan Marcus's user avatar
  • 39.3k
2 votes

Does the inverse square law apply to all lights, including light within a lens?

This answer is empirical. I will not try to make a mathematical one. This is only a series of statements. In general, the inverse square law applies to a point light. Every big diffusive light at ...
Rafael's user avatar
  • 25k
2 votes
Accepted

Does image distance affect resolution?

There's a general answer to your question. But based on something specific you said, there's another answer based on a misunderstanding. Specific issue: Mounting the lens too close to the image plane ...
scottbb's user avatar
  • 32.9k
2 votes

Why has no phone manufacturer tried a lens turret system yet?

Users don't want this. Users want simplicity. Manufacturers don't want this. Manufacturers don't want complex mechanisms, they want electronic/software solutions where possible. You are thinking like ...
osullic's user avatar
  • 12.5k
1 vote

What is the difference between working focus distance and infinity focus in Camera Lens (specially machine vision camera)

You have read the specifications wrong... but they are not written terribly clearly. It is a 50mm lens with a 200mm minimum working distance. It can focus from 200mm to infinity. Note that it is only ...
Steven Kersting's user avatar
1 vote

What is the difference between working focus distance and infinity focus in Camera Lens (specially machine vision camera)

No its because the lens cannot move close enough to the sensor(*). Its the same problem as SLR cameras using a macro extender rings on the lens. The camera can focus closer, but it's "far" ...
xenoid's user avatar
  • 21.5k
1 vote
Accepted

Calculating FOV for mismatched lens/sensor size

According to the sensor spec, it has 1920 * 1080 square pixels of 2.9µm size, giving a physical sensor size of 5.568mm * 3.132mm, a 16:9 aspect ratio a diagonal size of 6.388mm Plausibility check: ...
Ralf Kleberhoff's user avatar
1 vote

Why does viewing the sun through a telescope burn your eyes?

Light from a distant object like a star arrives at the telescope as a bundle of parallel rays. The front lens (objective lens) captures these rays. As they traverse the objective lens they are ...
Alan Marcus's user avatar
  • 39.3k
1 vote

Why does viewing the sun through a telescope burn your eyes?

I find xkcd‘s take on this very telling, it starts by asking a different question: How hot can you make something using optics? The answer is: You can‘t make something hotter using optics than the ...
Grimaldi's user avatar
  • 473
1 vote

DOF of line scan camera & lens

The circle of confusion is what you accept as tolerable blur. In the olden days of 35mm film photography, a common convention was to accept a 30µm diameter as "sharp enough". Translating ...
Ralf Kleberhoff's user avatar
1 vote
Accepted

Optical Vignetting

The vignette: If you were an insect walking about on film or image sensor and looking up at the camera lens during the exposure, you would see the aperture as an illuminated circle if on center (axis)....
Alan Marcus's user avatar
  • 39.3k
1 vote

Optical Vignetting

I don't fully understand all of the questions, but I'll answer what I can. Rays from off center do bend; the issue with the drawing is that it is including only selected rays. I.e. all points on the ...
Steven Kersting's user avatar
1 vote

Calculating bellows factor (etc) when using a magnifier lens

Bellows factor is about how extension changes the exit pupil of the lens and thus the light intensity at the image plane. Basically, if you move the lens farther away, the size of the exit pupil ...
Steven Kersting's user avatar
1 vote

Calculating bellows factor (etc) when using a magnifier lens

Bellows Factor: As you know, modern cameras are adjustable and allow focusing over a wide range of subject distance. However, many camera models prevent extreme close focusing. We are talking about ...
Alan Marcus's user avatar
  • 39.3k
1 vote

How to calculate the required working distance for an object to fill the camera sensor?

Imagine your camera lens as having only one glass element. Now draw an imaginary triangle from the boundaries of the image sensor to the center of this lens. You have traced out an image triangle. If ...
Alan Marcus's user avatar
  • 39.3k
1 vote

How to calculate the required working distance for an object to fill the camera sensor?

FL=(subject Distance/subject Size)Sensor axis, or FL=(D/S)Sa For example, say you want to fill the frame width on an APS body (24mm sensor width), taking a picture of a squirrel that is about .5m long ...
Steven Kersting's user avatar
1 vote

What are the theoretical minimum and maximum apertures?

Since this is 2 questions (narrowest aperture, and widest aperture, I'm answering this in 2 answers Narrowest Aperture For imaging systems in non-scientific applications (i.e., cameras taking ...
scottbb's user avatar
  • 32.9k

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