Sunset in Kruger

by MrFrench

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

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.

learn more… | top users | synonyms (1)

2
votes
3answers
1k views

What does “maximum aperture” mean in a camera spec? Where can I get the full aperture range?

I own a Canon S95, and am considering getting a newer model (e.g. Canon S110 or S120), and I'm comparing the specs. According to DPReview.com, the S95 has a maximum aperture of F2.0-F4.9, and the S110 ...
3
votes
1answer
171 views

Why is the center of image smudged with magenta/white at a small aperture?

I took two pictures with a Nikon D300 and a 17-55mm f/2.8G lens. Both pictures have been taken at ISO 200, aperture f/22 and shutter speed 1/8s. I used a tripod. The only difference between the two ...
5
votes
1answer
129 views

Which lenses show focus shift?

Some lenses, because of a design that includes uncorrected spherical aberration, shift their plane of focus backwards as the aperture is narrowed. This is most apparent at close focusing distances and ...
0
votes
4answers
3k views

What is the most versatile lens for the Sony NEX-6? [closed]

I received a Sony NEX-6 body (no-lens) over the holidays this year and I am looking to find the right lens to match. I am searching for the most versatile lens available for this camera. In other ...
5
votes
1answer
966 views

What makes the Zeiss Otus 1.4/55 so special?

The new Zeiss Otus 55mm f/1.4 is nearly $4000. With faster lenses from Canon (50mm f/1.2L) with autofocus, why is the zeiss lens more than twice that of the Canon counterpart?
0
votes
1answer
93 views

Optical focal length [duplicate]

i have a quick question. We have a machine which has a camera mounted above a board at 75cm. The cameras ability to focus on an object at 0 zoom is 1cm, and all full zoom 120cm. The zoom is build ...
1
vote
1answer
590 views

Size of the entrance pupil vs size of the aperture

I understand that the entrance pupil is the image of the aperture as seen from the front of the lens. However, is the size of the entrance pupil the same as the size of the effective aperture? In ...
1
vote
3answers
294 views

Can I estimate the light gathering power of a lens by measuring size of entrance pupil?

Supposing I have an unknown lens of which I don't know f/# and focal length. I want to estimate the total amount of light that my lens can collect which, I believe, is given by the solid angle that my ...
2
votes
1answer
150 views

What lens is needed to change the minimal focus distance length of my camera?

Here is my problem, I Have a scientific camera, a Sony Block FCB-EH6500, which has an automatic focus. The minimum focus distance is 1 cm when completely zoomed out and 120 cm when fully zoomed in. ...
2
votes
1answer
538 views

How do anamorphic lenses produce lens flare “streaks”?

For example: What contributes to this streaking? Why doesn't spherical lenses have this effect? How is it used in photography?
0
votes
1answer
127 views

How do focal distance reductors affect image quality?

I have a bunch of lovely old full frame K mount lenses (like the 50mm f1.2 and the 135mm f2.5) and the idea of using them in a proper mirrorless body (I have the K-01 and that's a hell of a brick) ...
1
vote
1answer
203 views

What's the difference between a diopter and an extension tube?

It seems both allow close up shots of a subject but what are the differences both physically and in use cases?
0
votes
1answer
76 views

Should a fisheye converter be sharp when I look through it directly?

I bought a fisheye converter some days ago. Now, I am unsure if such a converter should create a clear image if I look with my eye straight through it. I found a video on youtube with the hint that ...
12
votes
5answers
868 views

What lens characteristics contribute to attractive lens flare?

Some lenses give really harsh and unwanted flares. Some gives beautiful flares that add depth to an image. What's the science behind this?
4
votes
2answers
492 views

What are the theoretical minimum and maximum apertures?

Is there such a thing as a maximum aperture that a lens can be open to? What about a minimum aperture that it can be closed to? Do these concepts even make any sense? Is there a lens with the ...
8
votes
1answer
194 views

What kind of mirror in a mirror lens?

A normal mirror, that we see for example in an elevator, is a glass sheet with thin metal coating on the backside, so light reflecting from the metal surface goes first thru the glass. Metal mirror ...
4
votes
2answers
1k views

How can I get the image/sensor dimensions in mm to get Circle of Confusion from EXIF?

I need to get calculate some formulas based on Circle of Confusion and/or image dimensions (diagonal) in millimeters based on EXIF data only. IOW, I cannot say "this photo was shot with Canon 5D3 ...
-1
votes
1answer
881 views

How to calculate the magnification factor of an object to its image?

I have an object of size 37.5um x 37.5um, and captured a 640 x 480 resolution image of the object with a CMOS sensor. I see that the object is around 200 x 200 pixels in the image. How do I calculate ...
3
votes
0answers
158 views

Is this a Fata Morgana? [closed]

I took this photo. Above the horizon there is a thick line that looks like a cloud, but it surely isn't. Is this a Fata Morgana? What do you think? The Image
12
votes
4answers
710 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. ...
5
votes
3answers
531 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
votes
1answer
110 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 ...
3
votes
2answers
734 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 ...
1
vote
2answers
432 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 ...
19
votes
2answers
467 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 ...
7
votes
5answers
869 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?
3
votes
1answer
148 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
votes
2answers
957 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 ...
5
votes
2answers
202 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
votes
2answers
971 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 ...
5
votes
1answer
153 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 ...
14
votes
1answer
855 views

How does a macro lens focus so close?

How does a macro lens focus so closely and how is the system different to that of a non-macro lens?
1
vote
1answer
133 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? ...
1
vote
2answers
269 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 ...
2
votes
1answer
182 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 ...
0
votes
1answer
484 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 ...
7
votes
2answers
1k 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 ...
7
votes
5answers
901 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
votes
1answer
147 views

Is there a correspondence between Tilt-Angle and the angle of the Focus-Plane?

Tilt lenses have their tilt-range specified in degrees, typically around ±8°. It seems that this number corresponds to how much a lens physically tilts along one axis. The effect is to tilt the plane ...
11
votes
3answers
582 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? ...
14
votes
5answers
12k 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?
14
votes
1answer
253 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 ...
7
votes
3answers
2k 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 ...
17
votes
2answers
929 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
votes
1answer
2k 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 ...
10
votes
1answer
521 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 ...
11
votes
1answer
442 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 ...
12
votes
3answers
3k 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 ...
5
votes
4answers
6k 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 ...
2
votes
1answer
133 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 ...