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Of and relating to the specifics of lens construction and manufacture.

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3
votes
2answers
2k views

What does “Flat Field Focus” mean?

Looking at lenses, specifically sigma macro lenses, I noticed that it had a ""Flat Field" front lens element". What does this mean? And how is it different to the norm?
4
votes
2answers
214 views

Is having a lens with vignetting a real world negative for portrait lenses?

After reading this answer for another post: I don't mind the vignetting as it actually improves the look of portraits however if you're doing astrophotography what's the point in a lens that's ...
19
votes
3answers
1k views

Is it physically possible to build a long zoom (17-300 mm for example) at an aperture value of around 1.4 or 1.2?

I'm curious if the physics allow a company to build such a lens of course with good IQ, minimal color aberration, maximum sharpness, and little to none lens vignetting or edge softness
4
votes
5answers
914 views

What about lens construction influences bokeh?

I can understand how certain elements of a lens can correct an aberrations or make it sharper - but specifically, how do lens manufacturers influence the bokeh - the quality of the blur? There's a ...
4
votes
2answers
548 views

Are all DSLR lenses made of glass?

This question is about lenses to "big" DSLRs, not system or compact cameras with interchangeable lens. Are all lenses made of glass in DSLR? And if not, is there a notable difference between: kit ...
5
votes
3answers
390 views

Does the imaging circle size change when a lens zooms?

When a zoom lens is designed for a cropped (APS-C) imaging circle, does the imaging circle necessarily stay that small throughout the zoom range? It is easily understandable that a prime lens ...
13
votes
2answers
1k views

Retrofocus lens? What's that?

I saw that in Why do some people prefer 50mm to 35mm prime lenses? , in @MattGrum's answer: ... The 50mm is a simpler design compared to the retrofocus 35mm ... What's retrofocus?
2
votes
1answer
123 views

How are lenses made?

How are lenses and lens elements made? Also how are the lens elements and groups etc. arranged in the lens? In regards to the glass, are the elements ground, moulded or are there other techniques ...
5
votes
1answer
158 views

Where exactly would the focal length of a lens in the ray diagram fall?

If a lens is specified as (EF 50mm f/1.8), where exactly is the 50mm distance if I were to show it in a ray diagram? Considering that a lens is made up of multiple elements, I could not find a ...
4
votes
4answers
804 views

Which impacts the speed of focusing more, the lens or the camera body?

Speed is the larger concern, but a description of accuracy would be appreciated as well.
9
votes
3answers
573 views

Why are 50mm Lenses Cheaper?

There is no doubt that 50mm lenses, if all other variables are held equal, will beat any other lens when it comes to value for price (lower f/number). I want to know why. Possible theories I have ...
1
vote
1answer
1k views

What are screw drive lenses?

Are lenses known as screw drivers actually available?If so what are their features and why are they called so.Name some of the lens and their manufactures.
8
votes
1answer
348 views

Why does my Zeiss Hasselblad Distagon lens have a 5 blade diaphragm?

As we are all aware, the more blades there are in a lens’s diaphragm, the rounder the resulting hole can be made, and in turn this gives a more natural looking bokeh. So on receiving my recent ...
12
votes
1answer
561 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
votes
1answer
315 views

Below which focal length are lenses considered to be wide angle?

Focal length is the only factor that decides whether a lens is described as being normal or wide angle. Below which focal length are lenses considered to be wide angle? Is this focal length the same ...
3
votes
2answers
159 views

Why are lenses like the 40mm small and lightweight, but get larger and heavier as they get wider or narrower?

The 40mm/2.8 seems to be the smallest lens one can make. Also, why are f/2.8 lenses small and lightweight, but get larger and heavier as they get wider or narrower? Are these two things by ...
2
votes
3answers
283 views

Why not separate a tilt shift lens into two separate lenses?

When using a tilt shift lens I find myself using the two features of tilting and shifting for separate photos. If I want to control the depth of field such as in a portrait or macro shot I will tilt ...
0
votes
2answers
214 views

Does number of elements and groups of lens affect bokeh shape? [duplicate]

Possible Duplicate: What about lens construction influences bokeh? Does the circular or hexagonal shape of the bokeh depends on the number of elements and groups of the lens?? If not then ...
3
votes
2answers
209 views

Is there a difference in sharpness between aperture stops?

Is there a notable difference in sharpness between aperture stops of a lens? If so, where can I find that information for my Canon 550d Kit lenses?
25
votes
3answers
9k 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 ...
1
vote
3answers
260 views

Do lenses need to be made with more precision for Hasselblad's 60MPix camera?

One of Hasselblad's cameras has a Double-Full-Frame sensor. Does that mean that the lenses needed for it are incredibly complex to build (to have a sharp, high quality, abberation free image on the ...
48
votes
5answers
1k 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 ...
12
votes
1answer
221 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 ...
10
votes
1answer
406 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 ...
2
votes
1answer
1k 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
2answers
1k views

What is the benefit of an internal focus lens?

The "IF" in Pentax DA★ 200mm f/2.8 ED (IF) SDM stands for "Internal Focus". I know what this means: the lens doesn't change in size as I focus. (And it's true; it doesn't.) What's the point of this, ...
6
votes
1answer
337 views

How do ultrasonic motors allow continuous manual focus?

I understand the basic pros and cons of ultrasonic lens motors — called USM by Canon, SDM by Pentax, or SWM by Nikon. One of the chief benefits is that they allow "always on" manual focusing — you ...
7
votes
3answers
385 views

What is the limiting factor in lens construction when it comes to f-stop values?

This widely praised Nikon 105mm macro lens has a maximum f-stop value of 2.8. I've held it in my hands, it's a big lens. Meanwhile, this 50mm Nikon lens can go up to f/1.2, despite being 25% cheaper ...
4
votes
1answer
1k views

How to read a lens spot diagram?

How to read such a lens spot diagram?
11
votes
4answers
1k views

Is overall light gathering of a lens only dependant on aperture?

My impression is that the aperture value of a lens determines its light gathering ability, but I'm not sure I understand how it works... When considering light gathering in telescopes, it is ...
21
votes
3answers
1k views

When you zoom in with a lens on an SLR why does the lens go in then out?

I guess this is more a question of optics than photography but I just got an SLR with a basic 18-55 lens. I noticed that when going from 18 to 55 or 55 to 18 the lens physically comes back in and ...
-5
votes
5answers
3k views

How can I get bokeh with an aperture of 3.5 as my max?

I am trying to get DOF portraits of my daughter with my Nikon d7000, as per my previous post. I have zoomed in to 100mm or so and tried to get a large aperture but as I zoom, the camera decreases f# ...
13
votes
2answers
2k views

Why do zoom lenses and compact cameras have varied maximum aperture across the zoom range?

Why does a camera's maximum (allowed) aperture get smaller when you increase its zoom?
6
votes
1answer
348 views

Does focus breathing make a lens slower when close focusing?

I've heard that focal length of some lenses will become noticeably longer when focusing to a close distance, an effect called "focus breathing". Since f-number is focal length divided by diameter of ...
12
votes
4answers
4k views

How can a lens like a 18-55mm have more than one focal length?

How can a lens have a range of focal lengths? Shouldn't it be a single number? Isn't focal length supposed to be fixed for a lens of a particular shape and geometry? What am I missing? How many ...
30
votes
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 ...
27
votes
2answers
2k views

What is a pancake lens?

I've read about a "pancake lens" but don't really understand what that means. What the pros and cons of having a pancake vs. another type of lens? I'm thinking of getting a Panasonic Lumix DMC-GF1 ...
8
votes
1answer
285 views

How are ‘stills’ lenses calibrated differently to ‘motion picture’ lenses?

I was watching this promo video about the new Sony PMW-F3 and one of the DOPs mentioned that stills and motion picture lenses are calibrated differently. This is around the 4 minute mark in the video. ...
9
votes
4answers
480 views

Why do filter sizes vary for lenses of the same focal length?

I have a Nikkor 18-55 kit lens that has a 52mm filter, and recently I was looking that the 17-55 lens has a 77mm filter. Is it because the latter is a better quality lens? I assume a bigger circle ...
5
votes
7answers
5k views

Does the Nikkor 50mm f/1.4g perform better than the f/1.8d?

Looking into these two lenses, I'm getting the impression that for my Nikon D-90 with DX camera sensor that the f/1.8d would waste light that is cropped by the sensor whereas the f/1.4g would not as ...
7
votes
2answers
2k views

What are the advantages of a lens having a fixed maximum aperture?

What are the advantages of a lens having a Fixed Maximum Aperture? Previous answers have indicated that "pros tend to want constant apertures in zoom lenses". While in general lenses with a fixed ...
14
votes
9answers
2k views

Are all kit lenses poor? (And if so, why?)

Kerri Shotts says (emphasis mine): Also, if you already have great glass, there is little reason to get more (unless you need it for a certain reason). E.g., if you have a 70-200 f/4, don't rush ...
23
votes
5answers
2k views

What is special about lenses with f-number < 1?

Talking about fast lenses, Wikipedia mentions Nikon TV-Nikkor 35mm f/0.9-Fastest Nikon lens ever made Why don't, for example, f/0.5 lenses exist? Is there some special construction that comes ...
7
votes
3answers
613 views

Fast telephoto primes for APS-C mounts — would they make any sense?

I can see the benefit of designing and manufacturing a wide-angle lens specifically for APS-C sized sensors instead of full-frame sensors: you will get smaller, lighter, and cheaper lenses. But is it ...
2
votes
1answer
416 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 ...
11
votes
3answers
9k 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 ...
7
votes
4answers
451 views

Were lenses for film designed to focus different colors at different depths, and what does that mean for digital?

I was reading the book Adobe Photoshop CS5 for Photographers: The Ultimate Workshop by Martin Evening & Jeff Schewe (Focal Press. 2011) and read this paragraph about film lenses and DSLRs: … ...
13
votes
5answers
548 views

Why don't today's lenses come with a polarizer by default?

As I am now looking for a decent polarizer for my 18-105mm and 50mm (Nikon D80) I realized how important they are for outdoor photography. So why aren't they directly hard-mounted on every modern ...
2
votes
2answers
84 views

Resources for learning about digital cameras technical design?

I would like to learn more about the design of digital cameras in general, and DSLR in particular, from optics to sensors to mounts. Do you know any up-to-date resources (other than Wikipedia) where ...
21
votes
0answers
567 views

Is Image Stabilization better in the lens or the body? [duplicate]

Possible Duplicate: What is the difference between in-lens image stabilizing and in-sensor image stabilizing? Some DSLR manufacturers have image stabilization (IS) in the body of their ...