39

It depends. In many cases, it may actually be possible without any further visual aids in the picture. Many lenses, if not most, will show different longitudinal chromatic aberration in front of and behind the focus plane. If you scroll down just a little bit on the linked page, you will see this demonstrated with a picture of a focus test chart. With this ...


20

When the aperture is positioned to minimize vignetting, the bokeh shapes for objects that are too far is rotated by 180° compared with objects that are too near. (The aperture image is reflected through its center point.) If the arrangement of your aperture blades is not symmetric around the center point, you can try finding "reference bokeh" that are ...


15

Focal length is the distance between the lens and the sensor when the subject is in focus, not the distance to the subject. The term for the distance to the subject in focus is the focus distance and is measured from the image plane (sensor/film plane). The distance from the lens to the subject is called the working distance which can be significantly less ...


12

You are focusing on objects, which are reflected. So you are not focusing on reflected surface. You are interested in light rays, which go from object "through reflection" to your camera. Not only from reflective surface to camera. You can try to shot for example puddle - try to focus on ground and you will se that reflection is blurred. Then try to focus ...


11

According to the specifications, the 18-105 has a minimum focus distance of 45cm. This is measured from the focal plane of the camera, so is probably further away than 15-20cm from the lens. If you want to focus on things closer than that, you will need a macro lens, known as a micro lens in the Nikon world, or alternatively some extension tubes.


11

Many (possibly most) modern SLR lens systems return focus setting data to the camera. Potentially the precision of data returned could be high - something better than 1% of range would be possible and meaningful with modern systems. However, it appears that most if not all systems use a simple gray-coded* system with perhaps 16 steps. Number of steps ...


11

The equation assumes a simple single element lens that is bilaterally symmetrical. The camera lens, to mitigate the 7 major aberrations (shortcomings that degrade) is constructed using several individual glass lens elements. Some are positive in power, some with negative power. Some are air-spaced apart and some are cemented together. Because this array ...


7

Simple: You are focusing on the reflected subject, not the reflective surface. Ok, I'm not good at explaining this sort of stuff, I just understand how it works, but here's a drawing You see, when you are focusing on a subject, it's a reflection on the reflective surface, but the subject it's not there, it's further away, to explain better, lets say the ...


7

first of all, kudos on your effort to break a photography problem down to first principles. The discrepancy you've observed stems from a common oversimplification. Your 100mm Lens is actually what optical engineers refer to as a "lens assembly" As you likely know, it is comprised of multiple lens elements in groups working in tandem to form, refine, and ...


6

There's nothing obviously wrong with the image. You've got a very narrow depth of field, so the grass in the foreground and background is out of focus, but that's not surprising if you were shooting something relatively close at a long focal length. There's some chromatic aberration (red and purple fringing) in the unfocused areas, which also isn't ...


6

With a certain distance to the subject, it is in focus at a certain distance to the image sensor. As you move closer to the lens, the place it is in focus moves back. this is because the lens property to bend light is in principle fixed and as you move closer, you change the incoming angles. Naturally, something has to compensate for this, and the distance ...


6

My answer only deals with "human" ways in differentiation - that is: No software, only your eyes and hands. If I have no reference (as in: you blind me, you set the focus distance, and then I can only look through the viewfinder, but cannot change a thing), the answer is: it depends on what I can see. Take, for example, an alley of trees: one in front, one ...


5

Each lens has a minimum focus distance, which is 45cm for your lens, likely at 18mm, which is not bad for a superzoom. If you want to focus closer you would have to use a macro lens (which is a lens dedicated to close focusing) or use other means to allow your own lens to focus closer. Those are diopter filters and extension tubes. The three solutions can ...


5

The focus distance is the distance to the object via the reflecting surface. Try taking a photo of yourself in a mirror at various distances, the distance from the camera to you, via the mirror, is twice the distance to the mirror. Your camera will indicate the focus distance as that.


5

If the plane is too far or to close is just from the blur hard to say. the easiest way is to have objects in front and behind and see which one is sharp and so you could determine if it is too far or too close... this is the same way as it is done by calibrating the autofocus of a lens with a lenscal tool like this. without such objects its hard to tell it.


4

Without knowing the focal length, the exact lens added to the front of the existing one can't be calculated. However, what you want is called a "closeup lens". These are usually single-element convex lenses that mechanically mount as filters. First you have to find the diameter of the filter mount on the lens. This is usually written on the front of the ...


4

My Nikon 105mm drops from f/2.8 to f/4.5 at closest focus, so that sounds right. A post at betterfamilyphotos has a post where they say (emphasis mine): You would imagine that using a macro lens is the same as using a normal lens, and you would be right except that with a macro lens when you get close to 1x magnification, you start losing light. My ...


4

Yes for most camera systems: For Canon EOS, select EF and EF-S lenses transmit distance information through the EF mount. For Nikon, D- and G-type Nikkor lenses transmit distance information through the F mount; this is what the D designation means. G lenses are the same, only without an aperture ring. For Sony, all current lenses transmit distance ...


4

With just that lens you won't be able to focus on anything closer than 1.48 feet = 45 cm as per the lens specs. You might consider investing in a 100mm macro lens. Edit: To answer the second part of your question, it won't click the shutter because the camera knows that it's not focused. If you set the lens to manually focus the shutter button will take a ...


4

When a macro lens has a reproduction ratio of 1:1 an object with a given size will be reproduced at the image plane at the same size. This is irrespective of the focal length. The only difference is that a longer focal length will afford you the ability to achieve that reproduction ratio at a greater distance than the shorter focal length. The precise ...


4

The thin lens equation is 1/f = 1/do + 1/di, where f = focal length di = image distance = distance from lens to sensor do = object distance = distance from lens to subject. The focal length of a lens is defined by the thin lens equation, and it can be interpreted as a measure of the inverse strength of the lens. If you make a lens's optical surfaces more ...


3

Does focusing at infinity mean the sensor is at F? Yes. The definition of focal length is that it's the distance from the optical center of the lens to the image plane when the lens is focused at infinity. an object focused at infinity should correspond to the sensor position exactly at F True, although it's obviously the lens that moves and not the ...


3

There is absolutely nothing about this photo that requires a camera more advanced than your Canon 60D and a $100 lens. The basics are: Good lighting — a whole topic to itself Stop down the aperture a bit, which you can because lighting is good Nail focus, which is less critical because you stopped down In post-processing, crank sharpening and "clarity" up ...


2

Okay, I'm pretty sure this checks out, but haven't yet sanity-checked it with any physical lenses. Let's say 0 and 1 represent the distance scale / focus ring position at the MFD mark and infinity, respectively. Then 0.5, for instance, would mean turning the ring halfway between the extremities. Then, we have a hyperbolic curve like this: a = 1 - dmfd / ...


2

Take a look at the thin lens formula (image taken from Wikipedia): S1 here is the distance between the subject and the lens, and S2 is the distance from the lens to the spot where the image of the subject is formed. f is the focal length of the lens. You can see that as distance S1 gets smaller, S2 has to get larger to compensate. That is, as you move the ...


2

What you're seeing is know as bad bokeh. What's bokeh? It's a term that describes the quality of the out of focus areas in an image. What is good bokeh and what is bad bokeh? Umm... if you like the look of the out of focus areas it's good, if you don't, it's bad. That being said, characteristics of good bokeh include circular highlights with no "edge" to ...


2

I think you are seeing strong chromatic aberrations. Those come from different colors of light getting refracted slightly differently, so the focus points for the different colors are in different positions. The result is typically that parts of the shot off-center (and not necessarily out of focus) have purple and/or green halos. Green halos would not pop ...


2

I had the same problem with the EF 75-300 lens. I found out that the optics in the glass is made poorly and has a really bad drop off around the edges and when its out of focus the poor contrast on the images. I sold the lens for almost the price I paid for it and saved up for the EF 70-200 f2.8 II USM. Even the EF 70-200 f4 hands down better. The Price ...


2

From the specs, the lens's zoom is from 4.1mm (wide) to 16.4mm (zoomed in). Focal length is the only standard measurement of this, and that's almost universally in millimeters. (You can find it specified in inches if you go back to 19th century lenses.) The range 0–852 clearly doesn't correspond directly to focal length; it is probably stepper motor steps or ...


1

The short answer is, bigger is better! The image sensors of the various digital camera types vary in size. The so called full frame image sensor is a copycat of the image size yield of the esteemed 35mm film camera. These image sensors measure 24mm height by 36mm length. The full frame size is often called FX in the jargon of the industry. Other camera types ...


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