Vignetting Mystery


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#1
If somebody can explain the how, why etc. for this problem. Every time I take pictures in low light at f/4 I get vignetting but not at higher f stops???
Here's an example. These two were taken at 4:30am at ISO 100, 12mm. One is at f/4 and the other at f/11






For me the whole idea of a fast f/stop is to be able to shoot in low light. But???
 

#2
If somebody can explain the how, why etc. for this problem. Every time I take pictures in low light at f/4 I get vignetting but not at higher f stops???
Here's an example. These two were taken at 4:30am at ISO 100, 12mm. One is at f/4 and the other at f/11


For me the whole idea of a fast f/stop is to be able to shoot in low light. But???
You are shooting at a very short focal length, so that is probably contributing. What lens are you using? It makes perfect sense that your vignetting goes away when you stop down the aperture. Looking at your pictures, I have to say that the effect isn't too bad and can be easily fixed in LightRoom or PhotoShop by correcting for vignetting. Hope this helps :).
 

flipfreak

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#3
no mystery right? when u stop down, the vignetting disappears. thats normal. some lens vignette more when u use them wide open. can be inherent from the design or could be external factors as well.
 

Rashkae

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Nov 28, 2005
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#4
For me the whole idea of a fast f/stop is to be able to shoot in low light. But???
Aside from bokeh, the idea of a fast f-stop is to be able to achieve acceptable shutter speed in low light conditions. There is no "vignetting" reason associated with a large aperture lens.
 

#5
If somebody can explain the how, why etc. for this problem. Every time I take pictures in low light at f/4 I get vignetting but not at higher f stops???
Here's an example. These two were taken at 4:30am at ISO 100, 12mm. One is at f/4 and the other at f/11

For me the whole idea of a fast f/stop is to be able to shoot in low light. But???
Do you have any 'protective' filter (UV filter etc) on your lens? If yes, remove it and try again...
 

#6
Yep I forgot to mention. This was taken with the Tokina 12-24mm f/4 and no UV filter.
Still though I've done shots with it before "indoors" but not this early in the morning at f/4 at 12mm with no vignetting.
Oh and I do have LR and have easily done corrections with it, but would be nice if I didn't have to go that route for all my low light shots.
 

flipfreak

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#7
from the digital picture.

"What Is Lens Vignetting (or Light Fall-off)?

As seen in the example picture above, vignetting (or light fall-off) is the effect caused by more light reaching the center of an image than reaching the edges. There are several types of vignetting ...

Mechanical or physical vignetting is caused by an physical obstruction preventing light within the lens' field of view from reaching the camera's image sensor. Mechanical vignetting is perhaps the easiest form of vignetting to understand. The physical obstruction can be caused by the lens barrel, a filter, lens hood (improperly designed or misaligned) - or anything else in the way - preventing light from reaching the lens. Try looking through your viewfinder and blocking the light from reaching the edge of your lens (you can use your hand). The effect of mechanical vignetting is typically a strong, dark circular darkening most apparent in the corners of an image and it goes away as the lens is stopped down (narrower aperture). This is the easiest form of vignetting to understand.

Optical vignetting is caused by light hitting the lens aperture at a strong angle - an internal physical obstruction. This effect is often noticed in images taken with wide angle and wide aperture lenses used with wide open apertures. Even many of the best lenses have optical vignetting. Light hitting the lens directly from the front is allowed to pass through the aperture unobstructed while light hitting the lens from a strong angle is partially blocked by the aperture. A basketball passes through the hoop (aperture) much more easily if it is coming straight down into it (highly arced - or dunked) than if is is coming straight in from the side (at a hard angle - no arc). Stopping down the lens reduces or eliminates optical vignetting.

Pixel vignetting is yet another potential cause of image edge darkening. An image sensor is composed of millions of photon wells that measure/record the light hitting them. The photo wells, although extremely tiny, have a depth to them. Just as the late day sun does not hit the bottom of your trash can, light hitting the sensor at a strong angle may not hit the bottom of the photon wells. The strongest light angles will be found at the image edges. Reportedly, most manufacturers compensate for pixel vignetting in their sensor algorithms. Also, newer sensor designs may show decreased amounts of optical vignetting."
 

scorpioh

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Jul 17, 2007
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#9
Vignetting helps to frame the photo nicely also. it's not a bad thg after all...
 

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