# Tag Info

27

It is not just cheaper lenses. Many modern lenses, especially Auto Focus zoom lenses have this characteristic. There are several reasons for it: Unless a lens is parfocal the exact point of infinity focus shifts as the lens is zoomed in or out, and so obviously there will be a point where infinity for one focal length is past infinity for another. As ...

13

There are two ways "infinity focus" could be taken — "an infinite amount of focus, so everything possible is in focus", or "focused on something infinitely far away". In photography, it is specifically the second of these — infinity focus means your lens is focused so an infinitely-distant object would be sharp. When an object is infinitely far away, the ...

7

From my reading, the amount materials within a "handheld" lens expand / contract over, for example, 15C is so minimal it's not worth thinking about. However this really becomes an issue on large telescopes, both refracting and reflecting (even more so). Why? As a (rough) example, let's imagine a large reflecting telescope which has a body length of 3m, ...

7

This sort of testing is normally performed with an infinite conjugate optical system. One example of such is a/an (auto)collimator. Collimators and AutoCollimators can be used interchangably for the task of testing a lens at infinity. The testing procedure is simple. Obtain an (auto)collimator which is focused to infinity and contains a resolving power ...

6

To understand infinity focus, you must first understand both what depth of field (DoF) is as well as what it isn't. Regardless of the aperture of a lens, there will only be one distance that will be in focus. That is, there will only be one distance at which a point source of light will be focused to a single point on the recording medium. Point sources of ...

6

Infinity focus places the plane of focus sufficiently far that light from than plane reaching the lens hit the sensor are all parallel. To get as much in focus as possible, you should focus at the hyperfocal distance which depends on your sensor-size and lens aperture. If you focus at infinity, there will be less in focus but things may be acceptably sharp ...

6

Another possibility is to make a hartman mask for the lens. This method is used to find infinity focus for astrophotography. In use, you'd point it at the night sky so that you'll see trails of stars. Slowly rack the focus and take a long exposure to test that setting. As you approach infinity, the two star trails will merge into one line. Be sure to ...

6

If I'm getting the question correctly, it is about whether at infinity focus you ought to use wider apertures like f/1.4 or narrower apertures like f/11 to get the sharpest results? The answer is, it depends... First let's look at what depth of field actually is at infinity focus. The depth of field depends on three things: Focus distance, focal length, ...

5

I can guess about question 1. You say this is a point and shoot, so it is dumbed down for the masses. Past some distance, the built in flash won't do anything but run down the battery. There won't be enough light from the flash hitting the subject. Light intensity falls off with the square of the distance from the source. Another way to think of that is ...

5

A site called Catching the Light has a wealth of information on focusing. Here is the link for 17 methods of focusing to infinity.

5

I'd go to the aperture you want, go to live view, zoom in, and manually focus on the moon. For all practical purposes, it should be infinite. Mark it on the lens.

5

Past infinity sounds magical, but it's really not. Here's a thought experiment: what does something five feet away look like when you focus somewhere past that? Focusing past infinity simply means that you've focused further away than everything; nothing is in sharpest focus. Would it nearly instantly become unfocused, or would it be more or less gradual?...

4

The key to this answer is to first settle on the tolerable size of the circle of confusion. Most depth-of-field tables set this value at 1/1000 of the focal length. Kodak, for critical work set this value a 1/1750 of the focal length. For our purposes, we will use 1/1000. Thus if a 50mm lens is mounted the permissible size of the C of C is 0.05mm. This size ...

3

I had the same issue/idea as you and decided to see if I could alter the camera to focus father away. After taking it apart, the four spokes don't appear to allow adjustment of the focus. They don't turn. As the camera focuses the lens assembly (including this 4 spoke thing) moves closer to the sensor (for far away focus) and farther from the sensor (for ...

3

For landscape photography where the scene is at infinity (or where the depth of field is not an issue, e.g. you don't want the grass in the field to be in focus, only the far away mountain range matters), you should set the aperture to that value for which your particular lens used by your camera, is the sharpest. This can be as large as f/4 but more ...

3

If you need to have as much as possible including infinity sharp, it's better to focus at the hyperfocal distance instead of infinity. Then everything from half the hyperfocal distance to infinity is acceptably sharp. There are websites and smartphone apps to calculate that distance. I'm not sure what you mean by "It is my understanding that with manual ...

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

The problem has nothing to do with the image not being entirely focus but more of that it is soft. At f/4.0, there is a significant softness that the lens has. When you are looking at photo 100%, this softness becomes more pronounced. Details just become harder to capture for such a small portion of the image. Remember that when you are looking through the ...

3

Imagine light rays spreading out from a point and hitting the top and bottom of a lens, forming a triangle. Now the further away the point the longer the triangle. When a lens is set to focus at a certain distance it bends light rays at a certain angle into a point. Infinity focus means the lens brings parallel rays into focus. Now going back to the ...

3

My question was asked because it dealt with astrophotography. After asking the question I came across a site the was mentioned by @JohnCavan in another question called Catching the Light that has a wealth of information. One of those pages deals with focusing. @Smigol mentioned a few of them and here is the link for 17 other methods of focusing that may be ...

3

If we are talking about the phase-detection autofocus (the one you get through your viewfinder), then it is important to know that the actual AF-point is larger in area than the one you can see in your viewfinder. Therefore it would be best to look for a gap that is slightly bigger than your chosen AF-point. With contrast-detetction autofocus (LiveView), a ...

3

Whelp... Hiroshi Sugimoto did a series focused at what he refers to as "Twice Infinity". In his notes here he states- I set out to trace the beginnings of our age via architecture. Pushing out my old large-format camera’s focal length to twice-infinity―with no stops on the bellows rail, the view through the lens was an utter blur―I discovered that ...

3

If the lens can focus on closer objects, but not achieve infinity focus, the lens needs to be brought closer to the sensor or film plane. This often happens with adapted lenses that move the lens too far from the imaging plane. This also happens when you insert focusing bellows or extension tubes between a camera and its lens — you trade infinity focus for ...

2

Infinity focus is when the camera is set to focus on things at an infinite distance from the sensor plane. This is a property of the lens rather then the camera. If you have a DSLR or SLD then most - but not all - lenses can focus at infinity. If you lens has a focus distance scale, then the infinity will either be at the focus limit at the wide-end or ...

2

In astrophotography, the process of getting proper infinity focus can be done via a few methods: Optical device with direct visual measurement: a knife-edge focus or ronchi screen will allow the user to approach perfect focus on a point source of light. These devices are usually attached in place of the camera body for focus measurement. Magnifying ...

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I am not sure about the answer to Would the image circle size decrease if I was able to ditch the Barlow lens? But if you look at the JavaScript of that page you will see var sensorw = "Sensor Width" var sensorh = "Sensor Height" var maxres = "Max Res" var focleng = "Focal Length" var thisF = sensorw * 3438/focleng; var thisF2 = sensorh * 3438/focleng; ...

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Yes, you can manually focus the P520. The instructions are on page 2 of the reference section in the manual, at the back. The screen shot in the manual shows an infinity symbol, so I imagine it is possible to focus to infinity as well.

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What if I set my lens to Auto focus... Assuming you are focussing on stars bright enough for your autofocus to pick up. If not try to focus on the moon or some other bright object in the distance with autofocus. Since stars and star trails are very faint, to capture them properly throughout the frame you are fighting against two competing factors affecting ...

2

I think there's a couple of things going on here. Firstly some lenses exhibit focus shift, whereby the plane of sharpest focus moves as the lens is stopped down (this is usually due to residual spherical aberrations). Secondly camera live view feeds are subject to certain restrictions in the area that can be read from the sensor in real time, and will ...

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