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Optics is the science of light, and in photography often refers more specifically to to the properties and construction of lenses or the technical aspects of light sensors.

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846 views

Are mirror lenses appropriate for DSLR astrophotography?

There's a whole host of inexpensive mirror lenses available in the 500 mm - 800 mm range (this for example). They have slow max apertures (f/5.6-8) and a donut shaped bokeh (not a problem ...
17
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5answers
1k views

How do I find the aperture that produces the highest-quality images for a given lens?

I'm not talking about large aperture (f/1.8, f/2.8...), rather, about small apertures (f/18, f/20, f/23...). I read somewhere (actually I think it was on this site, but I don't exactly remember which ...
6
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3answers
789 views

How many blades does my lens' aperture diaphragm have when I get 12-pointed starbursts?

Here I figured that my camera has either three or six blades. But yesterday I took another shot at night with the same setup which has twelve srokes: The camera is a Canon 550D and I used the same ...
4
votes
1answer
303 views

What is the camera's influence on lenses' optical properties?

I installed my 50mm f/1.4 Nikon lens on my Olympus E-P1. I notice some properties of the lens changed — namely, magnification and DoF both increased. I understand magnification increases because of ...
7
votes
2answers
2k views

How can a prime lens focus on more than one plane?

By definition, a prime lens is a fixed lens system with a fixed focal length. Then, simple physics tells us that it should be able to focus only on one plane (at a fixed distance) in front of it. But ...
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4answers
4k views

Why aren't all viewfinders 100%?

We often see that a manufacturer's high-end (D)SLR models offer a "100% viewfinder," which shows the entire exposed frame, and allows precise composition with regard to objects near the edge of the ...
37
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2answers
16k views

What is the difference between a pentaprism and a pentamirror?

Higher-end SLR cameras include a pentaprism to transmit the image from the lens to the viewfinder, whereas lower-end SLR cameras use a pentamirror to accomplish the same task. What are the ...
22
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2answers
4k views

What is a zone plate?

I was looking into alternative methods of photography and I happened upon something called a 'zone plate.' Three questions: What is a zone plate? How does it work? What can I do with it?
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4answers
451 views

Why are some zoom lenses “soft” at either end of the focal length range?

As one reads about zoom lenses, a relatively common comment that comes up in reviews of some lenses (especially lower-priced lenses) is that the lens is not as sharp ("soft") at one or both ends of ...
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6answers
1k views

Is there an easy way to force chromatic aberration?

A couple of months ago I was playing with my camera and a magnifying glass and I noticed that this glass produced a very soft chromatic aberration. Here's an example: (Here is the full size, 18mp ...
10
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1answer
2k views

What are Barrel and Pincushion distortion and how are they corrected?

I have some questions regarding Barrel distortion and pincushion distortion. Since they are related I have put them in single post. I am aware that barrel distortion occurs more in wide-angle ...
11
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3answers
12k views

How does a spherical lens differ from an aspherical lens?

Many lenses (like the Pentax DA 15mm f/4 Limited, or the Nikon AF-S 35mm f/1.4G) are described as having "aspherical lens elements". Does this mean that regular lenses are spherical lenses? What's the ...
25
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3answers
3k views

Does changing the focal length change focus?

When using manual focus or back focus on D60, I sometimes zoom in the lens, set the focus, and then zoom out. Does changing the focal length (zooming out), also change the focus? In case the answer ...
8
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1answer
526 views

How is Bokeh created?

I am not asking how to create a bokeh effect. I found the answer to that quesiton here: Best way to get shaped bokeh? The answers on that question say you basically cut out an image from a piece of ...
17
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6answers
2k views

Can a smaller sensor's “crop factor” be used to calculate the exact increase in depth of field?

If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame ...
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2answers
645 views

What is the quantitative relation between f/# of the lens (aperture), exposure, and ISO?

Let's say we shoot with a DSLR camera and we have two interchangeable lenses. Lens #1 has aperture f/X, X between 1 and 2 (see below). Lens #2 is f/4.5. Same focal length and other characteristics as ...
2
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1answer
435 views

Relay lens for beam splitter

I have the setup that is shown in this figure. The view is from the top. I have a beam splitter which splits the light that is collected from a SLR lens. To be able to focus the light I have a ...
27
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3answers
2k views

What does a hexagonal sun tell us about the camera lens/sensor?

In this picture, we see that the sun comes out as a hexagon. I am sure it is not arbitrary. What does the hexagon tell us about the instrument that captured the image?
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3answers
2k views

What causes lens flare?

I heard a couple of years ago that only certain types of lens caused flare to appear, something related with the material and/or quality of the lens. Is this true? Which material/quality caused flare? ...
15
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2answers
1k views

What is the “Circle of Confusion?”

I know that when I want to calculate Depth of Field by hand one of the variable elements in that equation is the Circle of Confusion. In layman's terms, what is the "Circle of Confusion," how do I ...
44
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7answers
6k views

What is a “diffraction limit”?

I've seen the term used, but what is a "diffraction limit", when should I worry about it, and what undesirable effects are a result of it ?
19
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3answers
5k views

How does the human eye compare to modern cameras and lenses?

A goal in most photography is to present a scene which resembles what a person who had been there at that moment would have seen. Even when intentionally working outside of that, human vision is the ...
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1answer
2k views

What is the “Newton Effect”?

I was just chatting with a photographer friend of mine, and he mentioned wanting "anti-newton glass"... I didn't know what that was, so I did a google search. I quickly figured out that it was ...
31
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5answers
5k views

How do constant aperture lenses work?

Cheaper zoom lenses usually are faster at the wide end and slower at the long end (for example, the $150 Canon EF-S 18-55mm f/3.5-5.6). More expensive constant-aperture zoom lenses have the same ...
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6answers
12k views

Why do light sources appear as stars sometimes?

See for example this photo: From my experience, the longer the exposure the stronger can this effect be observed. Is this correct? Are there any other factors that influence the creation of these ...
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3answers
3k views

What makes a Carl Zeiss lens so special in a smartphone?

There are smartphones on the market that have a focus towards photography. Some are equipped with a Carl Zeiss lens. I have looked into Wikipedia, which tells me that they are a brand who produces ...
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2answers
9k views

What is the Chief Ray Angle (CRA)?

I want to select image sensors for a particular application. One term that I have come across regularly in their datasheets is the CRA. I was comparing 2 image sensors and although they were of ...
18
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12answers
16k views

How does the lens diameter influence photo quality?

I have tested two different 50mm lenses in my camera. One was a Nikkor 50mm ∅52mm. The other one was a Sigma 50mm ∅72mm. I took some pictures with both lenses using the same setup for aperture and ...
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7answers
7k views

What is bokeh, exactly?

I understand that "bokeh" refers to out-of-focus areas of an image — but there is obviously more to it than that. What does the term mean exactly? How well is bokeh really understood? Is it purely ...
28
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4answers
2k views

How does aperture work without “cropping” the image hitting the sensor?

I've been teaching myself the various settings in cameras and now have a much fuller understanding of how to use my camera effectively, but one thing is still bugging me. When the aperture size is ...
33
votes
2answers
2k views

How do I interpret an MTF Chart?

As part of how Canon (and other lens makers) give technical information about their lenses, they supply an MTF (Modulation Transfer Function) chart. How do I read and interpret what the chart is ...
13
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6answers
567 views

Does lens speed still increase meaningfully when the physical aperture is larger than the sensor size?

This question came to me this morning, thinking about 50mm lenses. I have the Pentax 50mm f/1.7 (manual) and it's a very nice lens, but would be considered (relatively) slow on 35mm film, and many ...
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5answers
1k views

How does a circular lens produce rectangular shots?

Is it something like the sensor captures a circular image and then what we get is the cropped version? Something like this: Or did I get it completely wrong?
10
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3answers
3k views

How many optical aberration types are there in lenses? And what are they?

Everyone hears something about chromatic aberration but are there any other types? What causes them?
13
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3answers
475 views

What is Chromatic Aberration?

What is Chromatic Aberration? Is it a physical part of the lens, or just an optical illusion?
20
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4answers
3k views

What is focal length and how does it affect my photos?

What is focal-length? Are focal-length and zoom synonymous? How does the focal length of a photo affect it?