Hot answers tagged

51

You've run over the diffraction limit. Light rays passing through a small hole will diverge and interfere with each other and a pattern emerges--a sort of banding where different frequencies/placement can cause separate rays to add up or negate each other. The smaller the opening gets, the larger this divergence/interference becomes. This pattern is called ...


48

As mentioned in the other answers, diffraction has led to unsharpness. To put this to the test, one can attempt to sharpen the image using deconvolution by using the point spread function that corresponds to F/29. For diffraction, we have (up to an overall normalization) P(s) = {J1[ πrs/(λF) ] / [ πrs/(λF) ] }2 where J1 is the Bessel function of the ...


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 ...


35

Actually, this is intentionally done and can be duplicated with any camera and flash combo (ish). To me, the second and third image seem indicative of a technique known as second curtain / rear curtain sync. The first appears to be good ol' flash during a long exposure...(more below)... In all of the examples, a decently long exposure (for the event) was ...


24

shutter speed 0.5 seconds This is likely to be a bit of your problem. The shutter causes vibration of the camera. So, too, does your hand pushing the release button. At faster speeds, this vibration does not affect the shot. Likewise, at very slow speeds (a few seconds +). But there’s a sweet spot somewhere between a second or two and ~1/30 where that ...


20

The blur is caused by the shutter being open for much longer than the duration of your flash. The orange color of the blur is due to the ambient lighting being much warmer in color than the light from your flash. Since the camera has almost certainly set white balance automatically to match your flash, the much dimmer and warmer ambient light has a very ...


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 ...


18

I don't have Photoshop, but there's an ancient open source project called refocus-it (for iterative refocus), which uses some of the same techniques as Photoshop's new-in-CS6 deblur feature. This should give better results than sharpening with unsharp mask or a high-pass filter. Below, I chose (after some experimentation) a radius of 3.1 and (since the image ...


18

Use more light. Open windows, turn on more room lights, bring in extra portable lights. Use a flash. You say there is "no chance" to use a flash, but since you gave no justification for that it remains valid advice. Added: I just looked at the manual you linked to, and right on the front page it clearly shows a popup flash. A spot light from almost ...


16

You appear to be using your lens (100-400/5-6.3) with the aperture wide open. I would expect the glow in your photos to be significantly reduced or absent stopped down to about F8. Many lenses "glow" when used wide open, especially in bright light with high contrast. It is likely associated with spherical aberration and is typically reduced or completely ...


15

Because of diffraction. f/29 is way too much for you to expect a sharp image. Try shooting the same thing at f/8 and you'll see the difference.


13

If you remember the exact radius of the Gaussian blur, and you processed and saved the images in a 16 bit or greater format then you can remove the blur by inverse filtering in Matlab. If you don't remember the radius, or you truncated the pixel values by working or saving the image as 8 bit (and then used lossy JPEG compression for good measure destroying ...


13

There is definitely something very wrong here. That's not a focus or DOF issue, but looks like the lens suffers from extremely strong field curvature. It's normal for a lens to be sharper in the center than around the edges, and this effect gets stronger with wide open aperture and at the extreme ends of the zoom range (your last sentence indicates that you ...


13

First, I'll talk about what cameras do normally, then about how motion affects this operation. In order for an image to be sharp and in focus, all light coming from a single point on the object being photographed must fall on a single point on the film or sensor. If you take a picture of a face, you want all of the light reflecting off the left eye fall on ...


12

No, a higher resolution sensor does not increase the difficulty of handheld shooting. It does mean that is is more difficult to realize the full potential of the higher resolution sensor, but that doesn't mean the results are worse than they would be with a lower resolution sensor.


12

From the comments, it seems like this is your problem — you're probably focusing past infinity. See Why do some lenses focus past infinity? Or, if you're not turning the ring all the way and instead relying on the marking, it may just be that the marking isn't precise enough. Try the suggestions at Where to focus when shooting landscapes? instead.


11

First of all you need to use a good resize algorithm for that case. Lanczos, or Photoshop's Bicucbic optimized for reduction. And then to make for better contrast around the letters you can use some output sharpening. Secondly, there is a minimum resolution you can use to render the fine letters. The book is a perfect example because of the different fonts ...


11

The fact you're seeing this with two very different bodies suggests to me it's in the lens. Long zooms tend to have a bunch of elements (anywhere from a dozen to twenty, in my experience). No lens coating is perfect, and no lens surface is perfect. Every time light passes through an air-glass or glass-glass interface at an element surface, there's a small ...


10

A sufficiently fast shutter would do it, but that also may very well not be a satalite photo. Google maps also uses arial photos and the detail of the plane in the photo seems too high and the plane too large in comparison to the ground for it to be taken from space. My guess is that the photo was taken from another plane, probably moving in a similar ...


10

Do the math. Let's say the plane is moving at 200 MPH, which is a plausible value right after takeoff or right before landing. Note that the flaps are extended, so one of these is the case. 200 MPH is 89 m/s. There is some blur. I'd say about 250 mm or less motion of the plane during the picture is about the limit that picture is showing us. That would ...


10

From the other question: Here's the list of things that influence depth of field the most (in this particular order): Subject distance, the closer the subject is, the shallower the DOF (think of macro) Focal length, the more millimeters, the shallower the DOF Aperture, the smaller the f-number, the shallower the DOF (written by Karel) and this is my ...


9

Bokeh means the visual looks of out-of-focus areas of a photograph taken using real world optics. For perfect optics an out of focus point of light (e.g. an out of focus start) would be a perfect disc. Real world optics are not perfect and a single point of light will not show up as a perfect disc in the photograph. Gaussian blur is a digital filter that is ...


9

The softness at the edges is definitely caused by a decentered lens. This just means one of the internal glass elements is not properly aligned with the others. Like so; (It could be any of the elements...this is just an example of the far left being off.) I'd recommend that you immediately send it in for repair to Canon. You can start here: http://www.usa....


9

The short version is you need not the "biggest aperture possible" but the right aperture given the distance and desired depth of field. There are a number of online depth of field calculators available (search for it, since these answers live a long time I hesitate to put specific links). Put in your focal length, distance, sensor information as ...


9

From the information provided in your comments, it sounds very much like the shutter speed was too low, possibly because your ISO was too low and the subject was moving faster then the shutter, hence the blur. I'd suggest increasing ISO and shutter speed. Point of note. The light may seem OK to a human eye, but an eye is considerably more sensitive then a ...


9

A diopter lens* like this is really only supposed to work at VERY close distances, which your unmodified phone or camera lens won't focus to (otherwise, there is no need to use a diopter). From the picture, it looks like you are holding the camera a two feet or more away from the subject - the phone can likely focus on that just fine without a diopter. Try ...


8

Without seeing an example image, it's hard to tell which of the following is the problem. Your lens is on manual focus. Note that having the camera's exposure dial on the green "Auto" is not the same thing as auto-focus. Auto-focus is usually controlled on the side of the lens itself with an "A/M" switch. The subject is moving too fast for your shutter ...


8

The three primary contributors of blur and/or softness in most pictures are: Camera motion Subject motion Incorrect focus Additional contributing factors can be: Narrow Depth of Field Diffraction Use of tilt/shift with a capable lens Chromatic Aberration Lens Distortion Misaligned/Decentered lens elements Misaligned lens mounting flange Poor lens design/...


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