We’re rewarding the question askers & reputations are being recalculated! Read more.

New answers tagged

2

As I understand the question, you're asking about lens sharpness/IQ when depth of field is not a concern. Light itself is sharpest when it is not bent through an aperture restriction, but that can't happen. So light is sharpest when it is bent the least... i.e. the largest aperture opening/smallest f#. But for that to actually be the case requires a lens ...


4

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, ...


0

I've just come across this (now almost) 9 year-old question. There is some good information in these answers, but many are quite old now, and none really answer the OP's original question: Can software auto-detect image focus? After reviewing the posts here, I found an application called Fast Raw Viewer that has at least a partial solution.


1

Most normal camera lenses are rectilinear. That means that straight lines in the 3D scene should show up as straight lines in the photo. If you photograph a scene with a rectilinear lens, then what you get is a perspective projection of the scene onto the image plane. Lines that are truly parallel to each other in the scene will not necessarily appear as ...


3

No, not from one picture. It could be tilted towards the camera (or away from it), and there is no way to see it in the shot.


3

I believe it's just a bad/distorted picture. After correcting the pincushion lens distortion and camera angle (roll/tilt), it appears to me that the tower is straight. The horizontal lines I added reference to things that should be straight/level, and what I corrected for. The vertical lines are perpendicular to reference the straightness/verticality of ...


3

The answer is maybe. It depends on whether the photos have required reference points to make the determination. If the required points exist on the photograph, yes. Verticality (plumb) is established as the line between the zenith (point overhead) and the nadir (centre of the planet). Any eccentricity from that is considered "tilted." The horizon is ...


2

Theoretically, you might be able to determine the tilt angle. However, more information besides the photos is necessary. You would need to know the exact coordinates of the camera and several other objects in the image (several points along the buildings in the foreground). The next problem is that lenses are not perfectly rectilinear, straight lines will ...


1

I hear that Microsoft has made 3D models of buildings just from using the huge corpus of photos available on the net so it is definitely possible. If you want to do that with 2 photos, just takes two pictures along two roughly orthogonal axes (for instance one from the North and one from the West), and if the minaret is vertical on both then it is vertical. ...


0

A split prism finder uses 50% of the available light for each side of the split image on the focus screen. With the advent of autofocus a significant portion of the available light is redirected to the autofocus module; which results in insufficient light for a 50/50 split at the focus screen. I.e. a split screen installed in a modern AF DSLR is prone to ...


1

Your assumption about analog vs. digital viewfinders is incorrect. Some digital cameras still use "two misaligned half circles" for focusing and some analog film cameras do not. "two misaligned half circles" for focusing is also called "Split Prism" and was a focusing aid used in most older, Manual Focus cameras. When Auto Focus lenses were developed for ...


2

The analog camera you use most likely has no autofocus and thus has a split prism. These are great for manual focusing, but not so great for auto exposure (AE), as AE is done after the focusing screen. Since AF usually works fast (and has a confirmation by LEDs), most cameras use plain focusing screens, though some professional cameras offer interchangeable ...


0

I calculated some values for a lens with a focal length of 25 mm. To focus to infinity, the sensor should be 25 mm away from the reference plane of the lens. A mounting error of + 0.001 mm shifts the infinity point to 625 m. An error of 0.01 mm to 62.5 m, 0.1 mm to 6.27 m and 1 mm to only 0.65 m. An error of + 0.5 mm shifts the infinity point to 1,27 m. I ...


1

If an ideal simple lens with focal length f is pointed at a subject at distance s, it will produce a focused image at distance 1/(1/f-1/s). For a subject at infinity, 1/s will be zero, so the distance will be 1/(1/f), i.e. distance f. For a subject which is at distance 2f, 1/s will be 1/2f, so the distance will be 1/(1/f-1/2f), i.e. 1/(1/2f), or 2f. ...


1

Honestly, you may be thinking in the wrong direction. Let me explain: Why you may not actually want a more pricey tripod More expensive tripods tend to be made of lighter materials (carbon fiber is a favorite, and it's what yours is made of). This is for the benefit of photojournalists (etc) that have to carry several cameras, lenses, and other gear. Every ...


40

If I have built my device with the correct distance between the flange and the optical plane, does this mean the (inexpensive) lens I am using is bad? If you had built your device using the proper specified flange distance of 17.526mm instead of rounding it off to 18mm you probably would not be asking this question. 0.474mm doesn't seem like much, but it ...


3

Potentially. It could also be that your measurements are slightly off. To find the perfect distance, you can focus on infinity, and then slowly move the lens nearer, until the picture is sharp. That is the correct distance; however, you should give it an extra tenth of a millimeter or two, to avoid issues with temperature changes or slight movement when ...


0

One difference I noted is the build quality of all the clamps locks and joints - if you, for example, look at an old-school Linhof/Schiansky, the clamps (and heads too) will take some force to operate, but will be as stiff as welded once fully engaged - and they seem to be designed to NOT easily wear out in any way that lets contact surfaces diminish or ...


9

If not, do I move the lens away or closer to the optical plane to fix the problem? If the lens will focus on near subjects, but not on a subject at "infinity," then that means that the lens is too far from the sensor. You need to move it closer.


1

Here is an example shot using a $20 Mini Endoscope, sometimes called a Borescope. It's not super quality but it produces real-time video so you can see what you are doing. It has a builtin ring of LED lights that you can control the intensity of, but this shot is just ambient room light. These are sold as smart phone plugins requiring a custom app to use ...


1

Consider getting a reverse ring to try to reverse the 50mm or the kit lens. There are really cheap options, without aperture control (you have to remove the lens while holding the aperture preview button...) Or more costly options, with full aperture control. Here is the result I got when reversing my 28mm 1.8 (on full frame... about 2-3x). If you do this + ...


1

No, you cannot get 6 inches of working distance with your lenses and close-up adapters. For a test, I put a 10 diopter close-up on my 50mm lens. The working distance is about 3 inches, too small for your use. Also note that magnification calculation is different for a camera compared to an eye magnifier. For a camera it is the ratio of image to sensor size. ...


Top 50 recent answers are included