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983 reputation
716
bio website
location ND
age 31
visits member for 2 years, 6 months
seen 6 hours ago

Apr
21
awarded  Popular Question
Apr
8
comment How can I make the most of entry level camera gear?
Stop reading sites where people discuss gear instead of pictures. Then you won't be unhappy about what you don't have ;-) What you have is still much more flexible (and gives better quality) than most new compacts. I used a Nikon D60 with a single 35 mm 1/1.8 lens for > 2 years and I was very happy with it. One of the things that gave me the biggest improvements was starting to shoot RAW and post-processing it. Also, instead of thinking about stuff you can't do (shoot small birds or do macro) focus on stuff you can do with your current setup. I tried some panoramas and time lapses.
Mar
25
comment Nikon 55-200mm or 50mm
Is this going to be your only lens? Or are you getting it together with a kit lens? If it will be your only lens, then the answer will necessarily have to be neither ... if not, it depends on what you like to do.
Mar
23
comment CMYK vs RGB - Can a DSLR take CMYK images?
You might want to read up on these: en.wikipedia.org/wiki/Subtractive_color and en.wikipedia.org/wiki/Additive_color
Mar
19
comment Does median blending / image stacking result in better or worse results than a long exposure?
@KartickVaddadi "But shouldn't the MEDIAN of 10 one-second exposures give less noise?" <-- If you consider the shot noise (Poisson), then taking the median will in fact result in higher noise than taking the mean. However, the median will effectively discard outliers, for example if a cosmic ray hit the sensor during exposure (not part of the short noise), while the mean won't. Some interesting reading on this here.
Mar
19
comment How does a camera implement different white balance modes?
You bring up an interesting point. It is not in fact obvious that the transformation should be an independent and linear scaling of the three channels. I would not expect it to be linear because the RGB values are not linearly related to the light intensity (I would however expect it to be independent). However, WP says that this is actually what is often being done in practice, though not always.
Mar
17
comment Might future advances in sensor technology reduce or eliminate noise?
@KirkBroadhurst Historically, the first model of light was as "rays" (geometrical optics). Then came wave optics. Then quantum mechanics---light is made of discrete units. It is interesting to think that phenomena related to each model (and not explainable by previous ones) do have practical significance in digital photography.
Mar
17
comment Might future advances in sensor technology reduce or eliminate noise?
@KirkBroadhurst That's the whole point: in low-light we aren't. Human vision is approximately logarithmic, and the "stop scale" is also logarithmic. One stop less light means half as many photons. If you start halving, you get to only a few photons very very quickly. If you're mathematically oriented you might want to read up on the Poisson process. Generally, if you have k photons on average per pixel, the magnitude of the pixel noise will be sqrt(k).
Mar
17
comment Photo stretched at corners?
Keeping straight lines straight is not the only kind of property one might desire from a projection. Other useful things are: preserving the angles, preserving areas, etc. Projections with these other properties won't keep straight lines (hence they have barrel distortion), but they produce a more natural look in the corners. This is why I said that if the lens has barrel distortion, then it will usually have a less severe stretching in the corners. So your first statement, that barrel distortion can cause this, is not quite accurate. In fact a lens with barrel distortion will stretch less.
Mar
17
comment Photo stretched at corners?
... projections e.g. in Hugin. What they often call "distortion free", meaning no barrel/pincushion distortion free, is projecting through a point. This is what the idealized thin lens (from middle-school optics) does. It has the property that straight lines in 3D get transformed to straight lines on the photo, but it also "stretches" the corners. This stretching (illustrated in the OP's photo) has nothing to do with "barrel distortion", which refers purely to those lines not being straight any more.
Mar
17
comment Photo stretched at corners?
Actually if the lens has more barrel distortion it will usually have less of this "stretching" (perspective) effect. "Distortion" (while standard terminology) is not the best word for these phenomena, as it implies that the picture doesn't show the subject "true to life", but in a "distorted" way. What actually happens is that the lens needs to project (part of) a sphere (spherical view) onto a plane (the photograph). There are many ways to do this, each with different properties. You can experiment with transforming a photo to various ...
Feb
24
comment Does a larger sensor resolution increase the difficulty of shooting hand-held?
The area ratio is not 2 but 1.5^2 = 2.25 and these two particular sensors have identical pixel pitch. That aside, doing any kind of comparison like this doesn't make sense unless you also talk about what focal length lenses are used on both. If the field of view is the same for both, then the higher resolution sensor will be able to detect smaller motion blur. If the focal lengths are the same for both (and thus the field of you will differ if the sensor sizes are also different) then the smaller pixel pitch sensor will be able to detect motion blur more easily.
Feb
24
answered Does a larger sensor resolution increase the difficulty of shooting hand-held?
Jan
31
awarded  Announcer
Dec
22
comment Demosaic data stored in TIFF
@mattdm Then instead of voting to close, you can vote to migrate it to the right place ... the problem came up in a practical application to photography, so I thought it's more likely I'll find an answer here than on DSP.SE, as more people here would want to do the same thing here. Looking at the other questions on this site I don't see why this is clearly off topic if asking for say noise reduction software is not off topic.
Dec
22
comment Demosaic data stored in TIFF
@mattdm It's not about programming, nor about image processing methods. The question is asking for a software tool to do something, like many other questions on this site.
Nov
14
comment What is the precise definition of SNR, as used by DxOmark?
That is not my question... It is clear to me why a larger sensor will show less noise when its image is viewed at the same size as the image from a smaller sensor. What is not clear is the precise meaning of the numbers DxO uses.
Nov
14
comment What is the precise definition of SNR, as used by DxOmark?
This is a general definition of SNR, but not the whole story. It doesn't explain why a large sensor with more pixels will have a higher snr than a smaller sensor with the same pixel pitch but correspondingly fewer pixels. The standard deviation alone is independent of the number of pixels for a give per pixel noise level. Please see my comment on the main question.
Nov
14
revised What is the precise definition of SNR, as used by DxOmark?
added 284 characters in body
Nov
14
revised What is the precise definition of SNR, as used by DxOmark?
added 15 characters in body