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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photo of reflection in magnifying mirror shows normal magnification. Why?
I just took a picture of myself in one of those magnifying shaving mirrors and in the photo I am unmagnified! Why is this?
Thanks for any insight!
11
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4answers
246 views
Why aren't lenses designed with extra large apertures for autofocus beyond what's used for imaging?
Historically, designing large-aperture lenses has been difficult because correcting the optical aberrations that arise from large apertures requires complex designs and very large amounts of glass. ...
7
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5answers
426 views
Why not have the diaphragm in camera body instead of the lens?
Why is the diaphragm to control the amount of light entering the camera typically in the lens and not the camera body itself?
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6answers
1k 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 ...
21
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2answers
2k 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?
3
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3answers
209 views
What does it mean that a lens is x millimeters?
Every lens has different focal length in terms of millimeter so if I have a 100mm lens, what does that refer to? Does it mean the length of the lens itself is going to be 4 inches long, or does this ...
4
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1answer
93 views
Why do focusing aids darken when not looked at directly?
Many users of (D)SLRs equipped with a split image rangefinder or, to a lesser extent, with microprisms will notice how they have a tendency to appear dark in less than optimal conditions, such as ...
7
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3answers
330 views
What are ED elements?
I find that some lenses are indicated with the letters "ED", referring to some special type of lens element. What are ED elements, and what advantages do they bring?
Note that this question isn't ...
11
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5answers
2k views
What is “infinity focus”?
I have been reading a bit about astrophotography and the term infinity focus keeps coming up. What is infinity focus and how do you set the camera to infinity focus?
3
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2answers
108 views
What's the difference between real and effective aperture?
I understand that the simple idea that f-stop is focal length divided by aperture really applies to a simple single-glass lens, not the compound lens systems used to provide good image quality in ...
26
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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?
11
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3answers
370 views
How does the D800E reverse the effect of an antialiasing filter by adding another filter?
According to http://mansurovs.com/nikon-d800-vs-d800e the D800E differs from the D800 in that one of the layers of the filter reverses the effect of the initial low-pass filter. How does this work?
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2answers
131 views
What does it mean for a telecentric lens to be focused to infinity?
I have a question about a telecentric lens Ive been studying (for physics research!) and was wondering if you guys could help clear some cobwebs in my head. For starters, I am simplifying the TC lens ...
44
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4answers
2k 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 ...
18
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2answers
380 views
How do graduated ND filters actually work?
My question stems from the fact that the surface of the filter is completely out of focus.
My understanding is that light from any one point of the subject hits the lens all over... some of it ...
9
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4answers
334 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 ...
32
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6answers
3k 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 ?
7
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6answers
2k views
Technically, why is the out of focus area blurred more when using a bigger aperture?
I'm wondering, technically, why and how does the out of focus areas blur more when using a bigger aperture. I think it'd help a lot if I presented a problem that's been driving me nuts for a long ...
3
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1answer
79 views
Does lens focus affect the appearance of sensor dust?
I know that aperture affects the appearance of dust on a camera's sensor (or, technically, the filter in front of the sensor), but does focus matter at all?
Since the dust is behind the lens, I ...
15
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2answers
390 views
Does a specific f number across all lenses denote same amount of light?
When we say a light source emits 1500 lumens of light, it does not really matter if the light source is incandescent, CFL, diode etc. Similarly, when I say f/1.8 can I assume that all lenses pass the ...
26
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4answers
1k 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 ...
4
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2answers
130 views
Why do the Nikkor non-AI 135mm vs 50mm f/1.8 work differently when I look directly through the lens?
I recently purchased an old Nikkor 135 f/2.8 non-AI lens. Beautiful lens, but the closest focal distance is about five feet.
I noticed that it will 'focus' at about 4 inches as well. If I hold the ...
4
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2answers
358 views
Why does calculated distance of an object in an image vary when zooming?
I would like to calculate the distance of an object from my camera, so i used the formula given in this question and I got a very good answer, but I've found that when I zoom and take the picture and ...
16
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11answers
9k 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 ...
3
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1answer
97 views
Is diffraction an issue with macro lenses?
I'm looking to try out macro photography and have a rental of the Canon 100mm 2.8L IS and the MT-24EX flash to try out on my Canon 7D.
I've been reading that with the flash, you can stop down to ...
32
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4answers
6k 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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1answer
87 views
Macro mode: Should I make sure the lens is all zoomed out?
It appears that on most compact digital cameras, the macro mode (flower symbol) works best (or only) when the zoom lens is at the widest setting (comparable to e.g. 35 mm).
What is the reason? ...
23
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3answers
5k views
What does the number of elements and groups in a lens mean?
All lens specifications include a statement of how many elements the lens contains, and in how many groups, for example:
Nikon AF-S VR Zoom-NIKKOR 70-300 mm 1:4,5-5,6G: 17 elements in 12 groups (two ...
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2answers
208 views
Is it worth it to read The Book of Optics
Is it actually worth it to read the Book of Optics by Alhazen to get basic knowledge about Optics? I know it's way too old but this book was important in the optics field. Also where can I find it ...
4
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1answer
456 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 ...
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1answer
215 views
Where are the principal planes located in a camera lens?
I want to find locations of the principal planes of a camera lens. I have looked at the specification for my lens here and here, but did not find what I need.
But there are many other parameters in ...
44
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5answers
885 views
Is there development in the world of lenses?
Now, I'm not an expert, so if this post makes you laugh, you're welcome. Still, as far as I know there are basically two components that determine the potential quality of a camera's photos:
Sensor
...
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1answer
136 views
How Do DxO Lens Ratings compare between systems?
Looking for new camera system with changing lenses (DSLR or SLD) I find DxOMark also has rating for lenses: http://www.dxomark.com/index.php/Lenses/Camera-Lens-Ratings
What do the results numbers ...
7
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5answers
546 views
What would be a good book for optics?
I would like to refresh my knowledge about optics. I studied optics back in the university but I almost forgot everything. What would be a good book to do that?
6
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4answers
508 views
Is it possible for a lens to produce too much contrast?
I came across a complaint that a certain lens produces too much contrast. The lens was described as rendering "cartoonish" contrast when shooting a portrait with diffused light from a window, where ...
12
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1answer
202 views
What lens design limits derive from the width of the lens mount?
I'm familiar with the lens design limitations imposed by the flange-to-focal-plane distance. But what constraints are caused by the width of the lens mount (that is, the size of the hole in the ...
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3answers
2k views
What is the technical difference between focus and zooming?
This may look like a silly question but I don't know what the difference between zooming and focusing is. Zooming in will usually let me have fewer subjects in the scene while zooming out will allow ...
19
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4answers
1k 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?
2
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3answers
492 views
How does a short flange back distance improve image quality?
In the description for the new lens mount for their X-Pro series, Fujifilm says:
1: Specifically designed to maximize the mirrorless design of the body, the X-Mount has a short flange back ...
10
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1answer
279 views
How do I design a conceptual lens schematic?
I would like to attempt to create a schematic for a simple or small compound lens, but the process seems very daunting. I have thoroughly read 'Science for the Curious Photographer:
An Introduction to ...
15
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2answers
530 views
Do rounded edges on aperture blades improve image sharpness, and how?
In the description for the XF lenses for its new X-Pro system, Fujifilm crows:
The [XF lenses] all offer precise control over depth-of-field and deliver excellent out-of-focus bokeh thanks to the ...
2
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1answer
589 views
How does the quantity of elements and blades in a lens affect the optics?
I am trying to get a greater understanding of how lenses work. Basically I bought this lens, the Sigma 10-20 f4-5.6:
The construction has really fascinated me. 14 Elements in 10 Groups?! What ...
11
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4answers
1k views
What is the reference point that the focal length of a lens is calculated from?
I understand the idea of a focal length for a single lens, i e the distance from the lens to the point at which parallel rays of light converge. However, in the case of a photographic lens with ...
8
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1answer
262 views
Why do mirror lenses have poor contrast?
I was reading this question on mirror lenses and the answers taught me a lot about mirror lenses. It is pretty obvious to me why they have donut bokeh (central obstruction) and why they are fixed ...
4
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1answer
229 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 ...
5
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3answers
2k views
Why are objects far away inverted through a lens but not through the viewfinder?
When I look through a lens the image of objects far away are inverted but when looking the the viewfinder on my camera they are not. Why is this?
I am having a hard time understanding why objects far ...
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1answer
100 views
Why does an aperture crop the image when you look through a lens itself but not when you look through the viewfinder?
I have been studying lenses for two days now and the aperture is very confusing.
Based on the question here it appears that the aperture should not crop the image at all but when I look through a lens ...
12
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3answers
367 views
What is Chromatic Aberration?
What is Chromatic Aberration? Is it a physical part of the lens, or just an optical illusion?
4
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4answers
488 views
Do bigger focal lengths capture more light?
I never understood what the f really stands for in the f-stop values, like f/1.8. Wikipedia explains it in various articles, but I still find it very confusing. What I understand, though, is that it ...
2
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2answers
659 views
Do lenses affect color fidelity?
It seems to me that my costlier (Tamron 90 f/2.8 macro) lens gives better colors than my cheap Canon 18-55 IS kit lens.
So does lens matter for color quality? What physical processes are involved in ...
