India Point Park

India Point Park
by matt-ball                

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Feb
13
comment External power for compact camera?
Is your kit also for Nikon cameras? Do you know if the plug it uses is a special proprietary one or a standard USB? (EN-EL12 uses less than 5 V). I'm ultimately looking to power both the camera and a Raspberry Pi from a large USB-compatible 5 V external battery.
Feb
13
comment How can I detect upscaled photos?
You can try taking the Fourier transform of the image and looking at the presence of high frequency components. Upscaled images won't have much of high-frequency components. Beware though that JPEG compression also removes some of these. I just tried this method and it seems to be fairly sensitive to down- then up-scaling. It will take a fair bit of work to make it reliable though.
Feb
13
comment External power for compact camera?
I wonder how you found that. I just spent 20 minutes googling in the hope of finding something like this!
Feb
11
comment What *exactly* is white balance?
There's some interesting info here, e.g. page 58 and onwards. It's a pity I don't have time to read it right now :(
Feb
11
comment What *exactly* is white balance?
Sorry if my comment lead you to believe that I have the answers, I don't :) I don't understand how human perception works, and this is an interesting question. A keyword you can search for is "chromatic adaptation". The scientific field studying perception is called "psychophysics".
Feb
11
comment What *exactly* is white balance?
"Why do we 'correct' this" <-- because our eyes (or rather brains) do as well. What's relevant for humans (or other creatures) is primarily the colour of objects, not the colour of light reflected by objects. So the brain corrects for light sources of different colours to be able to recognize colours/objects better. The purpose of white balance correction in cameras is to imitate this and produce photos that look "natural". There's no fundamental laws of physics behind this, it's all about imitating our human perception.
Feb
4
comment In what practical applications is the position of the sensor plane relevant?
Can you elaborate on how? I can see how it could be done for a thin lens, assuming we know the precise focal length. But with a complex optical system made of many (not so thin) lens elements, it's not clear to me how this would be done.
Jan
27
comment In what practical applications is the position of the sensor plane relevant?
@user35658 Thanks, that's interesting. So is that how people used to work with macro before TTL metering? Why don't you post an answer?
Jan
27
comment How can I find the sensor position on my camera?
I answered yours, can you answer mine? :-)
Jan
26
comment How does autofocus deal with the time to change aperture and raise mirror?
@Alec I am sorry, I should have not appeared so argumentative. I deleted irrelevant comments. "Phase detect AF" works the same way as split-prism focusing screens, which you can google for if you are interested.
Jan
26
comment How does autofocus deal with the time to change aperture and raise mirror?
"uses the phase of light and diffraction to work out when it is in focus" <-- this is not correct. The word phase in "phase detect autofocus" refers to something completely different (and yes, I do think it's a stupid name for it, but that's what engineers chose to call it...) It has absolutely nothing to do with the wave nature of light. If you're curious how it works, the illustration in the Wikipedia article is very helpful
Jan
25
comment Does focal length matter for a macro lense when use for close-up photos
The longer the focal length, the further you can be when at 1:1 magnification. This is important when photographing insects that can get startled and fly away. Focal length also determines the angle of view, which doesn't matter if you want to isolate the subject (typical macro), but becomes important if you want to show a creature in its environment. That's only really possible with wide angle lenses which don't usually go to 1:1 magnification. For the usual 60-100 mm range the subject is pretty much isolated.
Jan
23
comment Is it normal for a fast prime to exhibit purple fringing in middle of the image?
Actually axial chromatic aberration (as seen in the OP's example) is not easily fixable. Only lateral CA is. Lateral CA is usually well-corrected on high-end optics, but axial CA is not.
Jan
21
comment Is there a correct way to swap lenses?
@MattGrum There's a difference between dust and dust though. Windy sandy beaches come to mind. Silica sand can scratch glass.
Jan
15
comment Shooting full manual during an event or function
@TiaanRossouw I really don't see any advantage to use full manual exept in extreme situations when the camera's metering cannot be used (e.g. very long exposure, astro-landscape, etc.) It certainly doesn't give any "creative control" as some claim. There are three parameters that affect exposure: aperture, shutter speed and ISO. You can set two of them and let the camera adjust the third one. Then you have the choice to use matrix metering and leave the decision fully to the camera, or use spot metering, choose the spot to meter on yourself, and use exposure compensation. This is slower.
Jan
14
comment Shooting full manual during an event or function
What advantage are you hoping to gain from using full manual, ignoring the camera's built-in metering and judging light by eye? From the question I get the impression that you believe that using precise and reliable metering is somehow going to result in worse pictures than just judging "by eye".
Jan
12
comment D7100: How to adjust default settings?
He wants to quality to be reset to RAW instead of JPEG when he presses the two green buttons.
Jan
12
comment D7100: How to adjust default settings?
Wasn't he asking about resetting all setting to defaults, except the quality, which should be kept at RAW?
Jan
12
comment What can you do with Lightroom catalog files if Adobe stops support for Lightroom?
Open source projects get abandoned too. I'd think that a small open source raw converter with only a few hobbyist users is much more likely to become unsupported than the most popular commercial option that many businesses depend on.
Jan
5
comment Why don't sensors on satellites and rovers degrade as quickly as DSLRs on the space station?
"but video cameras last much longer" <- do you have a reference? "sensors on satellites don't degrade as quickly" <- again, do you have a reference? It seems they do degrade, but would be much more expensive and much more trouble to replace. People come and go on the ISS and bringing a new DSLR every couple of years is not particularly costly (compared to full mission costs). That article I linked is precisely about sensor degradation on Hubble.