Alley in Pisa, Italy

by Lars Kotthoff

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bio website mattgrum.com
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visits member for 3 years, 10 months
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Jul
12
awarded  resolution
Jul
11
answered Do you lose the increased sharpness of not having an AA filter if downscaling?
Jul
9
comment Foveon x3 sensor
@KendallHelmstetterGelner this isn't a discussion forum, so that's all for now I'm going to update my answer when I get a chance and provide sources for everything, I'm not making all this up - I very nearly bought a DP2M, and did a lot of research.
Jul
9
comment Foveon x3 sensor
@KendallHelmstetterGelner I meant a yellow object in an image contains red and green. Also you missed the point entirely, red and green don't measure the same spatial location, but when the red and green response increase together then you can use the green values to reliably estimate what the missing red values are and vice versa. So you get 33.75MP of red and green data, and you only need to "guess" 1 in every 4 pixels where there is a blue sensor which doesn't record useful information for yellow objects. That's a lot more than the 15MP of red and green you get from the X3.
Jul
8
comment Is there an automated way to create composites from multiple images of a moving object?
I think you might have it the wrong way round, the question was asking about a fixed camera and moving object, the object should appear many times in the final image in different positions. Pick up any snowboarding magazine for an example of this effect!
Jul
8
answered Is there an automated way to create composites from multiple images of a moving object?
Jul
8
comment Foveon x3 sensor
@KendallHelmstetterGelner With 45MP total, in the worst case (e.g. only red light) you get 11.25MP out of the Bayer and 15MP out of the X3. In the best case (e.g. a monochrome scene) you still get 15MP out of the X3 but get 45MP out of the Bayer! Yes most scenes have colour elements. A yellow object contains red & green light, when the brightness of yellow changes, red & green change by the same ammount, and demosaicing can fill in the missing red values using green of which there are 22.5MP! So it's really a case of fixed 15MP, or between 11.25MP and 45MP, averaging somewhere in the middle.
Jul
8
comment Foveon x3 sensor
@KendallHelmstetterGelner You mention Bayer sensors "topping out" in resolution in the same sentence as the Foveon Quattro - the design of which was necessary to fight a fundamental limitation in the X3 design, in that light is defocused as it penetrates deeper into the sensor! A perfectly focused image will appear out of focus if you move the sensor backwards even slightly. The same effect happens inside the X3, which is why the Quattro reduced the resolution of the lower layers. The Bayer sensor is only limited by manufactures' unwillingness to push resolution due to consumer misconceptions.
Jul
7
comment How do I take a photo like this (very bright)?
It's often repeated in answers to similar questions, but you don't generally need additional light or reflectors when shooting into a really low sun, the sun's brightness is greatly reduced and the open sky is usually bright enough to provide diffused light on your subject.
Jul
7
answered How do I take a photo like this (very bright)?
Jul
4
awarded  Nice Answer
Jul
4
comment How to photograph a lightbulb?
It's funny you should mention that last line, as as 3D renderings have become better and more realistic, they are increasingly being used instead of actual product photos!
Jul
4
answered Synthetic bokeh: linearly intensify bokeh/blur from e.g. detected contrast or bokeh circle sizes
Jul
2
comment Why is a camera's dynamic range expressed as its photosite capacity divided by the read noise level?
The term for the number of discrete grey levels is the "tonal range", I can see why people confuse it with dynamic range.
Jun
30
answered Is a Canon 50mm 1.4 lens only meant to focus close range?
Jun
29
comment How does an octobox differ from a rectangular softbox?
You can put a desk lamp in a softbox, bus as I stated it's not going to be bright enough to be much use, unless your ambient light is very low.
Jun
27
revised What causes longitudinal chromatic aberration on Nikon 50mm f/1.4D?
added 14 characters in body
Jun
27
comment What causes longitudinal chromatic aberration on Nikon 50mm f/1.4D?
@PicturePerformer ah yes the Defringe option, which attempts to remove any colour fringing, be it longitudinal CA, lateral CA or purple fringing. I turned it off for all images when I found it was turning the leaves of my trees grey. Would probably work for the image in question though!
Jun
27
comment If TTL only preflashes once, how does it get correct exposure immediately after?
The short answer is that it's pretty dumb and gets it wrong on a regular basis! If you shoot somebody in a high vis jacket, it sees the flash bounce straight back off one of the reflecting strips, thinks "wow there's a lot of flash coming back, I don't need much power at all" and then ends up massively underexposing the photo.
Jun
27
answered Using a set formula to measure distance in a photo but the answers are coming out much smaller than expected?