@ravnostic
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ravnostic
ParticipantDue to my inability to locate the set of photos I took sometime earlier this year that would surely win this contest in 1st, 2nd, and 3rd place, I’m settling for some bees from previous contests (well, there’s one new one, but only Star Trek geeks will like it and there aren’t any of them on Fark.)
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ParticipantI don’t know that we’ve really had a grain discussion on Farktography but for this contest I’m totally cool with grain.
/2 cents
post election, I’m hoping this refers to alcohol….
//damn; you mean I still have to process my shots?
November 6, 2012 at 1:53 pm in reply to: Recent work – some landscapes, some cars, some other stuff #49556ParticipantLove the first 4 (of course, I’d already mentioned the third over ‘there’). Man, I wish I had fog. I have to drive 3 hours for fog.
ParticipantSheet–I meant “your wife’s loss” of course. Pass on my condolences, will ya? Please do get me the details on the scope, but just the basics. Can’t say I’ll grab it, but I really would like a wider FOV; if it’s just a run-of-the mill refractor, it probably wouldn’t fit the bill, though.
ParticipantSorry for your mom’s loss, caradoc; that must be hard for her. 🙁 My dad’s 4th cancer surgery is tomorrow and I really get emotional when I hear of others who’ve lost their folks; it’s inevitable, of course, but that doesn’t make it easy.
I’m not familiar with the model; will have to look it up; might be good for a piggy-back.
ParticipantI have ideas…
That image, though, is totally real.
ParticipantI’m happy with this image of the Pinwheel Galaxy.
https://plus.google.com/photos/107857888121727893520/albums/5643774762113128657/5807412143156232466 😀
ParticipantWell then, my theory is blown (pardon THAT pun); because #3 had a wedding band…
ParticipantStandard f’graphy rules apply, but ‘in all their grainy goodness’ confusses me, then. I’m guessing that photoshop is of course out, but pp’g for ‘grain’ is in? Please explain, as you would to a child….
(I’m certain I haz 2 for this, though fuggin’ ST is back and posting on time will be iffy at best, for the next 4 months…why don’t we just get rid of ST and call DST the standard, anywayz?)
Participantfriggin’ tease. Which one (top or bottom) are you pretty sure about?
//looks like the third in the 5-plex is the same guy as the bottom of the last, no?
ParticipantOkay, the portraits above this latest are sublime; really really great (esp. the top two; the girl with the bow being my fav) but…
this last one….now that’s great acting!!
//they are actors, right? You’re not branching out into soft homoerotic porn, are you? And if so…need a 2nd shooter? (pun intended)
ParticipantThanks, Z^0. Incidently, came across this the other minute, and it’s the best explanation I’ve seen for darks, flats, and biases. I don’t completely agree on every point, but the guts of it is perfect, and to post, I need to do so in it’s entirety (legally, at least)
Copyright Pertti Tapola 2005
This text may be freely distributed without charge to anyone. For
that purpose it may be put on a web site, provided that this header is
included and the contents is not changed.This is not a complete guide but rather a checklist. For deeper
understanding of astronomical image calibration, I recommend reading a
good book, e.g. “Handbook of Astronomical Image Processing” which is a
very thorough and complete treatment of the subject.
Here is a short reference guide into different kinds of frames:Dark
====What
– reflects the camera-induced noise,
– temperature, exposure time and ISO setting -sensitive,
– camera-specific,
– aperture, telescope etc. have no effect so they are not needed.How
– no light coming in (use lens or body cap) and block the viewfinder as well,
– exposure time and ISO setting the same as for light frames,
– near the same temperature as light frames,
– take as many as you can and average-combine them.Use
– whenever the temperature, ISO and exposure time is the same,
– for the camera they were taken with (with whatever scope, filters, etc),
– ImagesPlus “Auto” dark calibration matches across exposure times and
also somewhat across ISO and temperature,
– if you have perfect tracking (=autoguiding) you may need upto 5 times
as many darks as light frames,
– with nonperfect tracking (some movement between each light frame),
or dithering between each light frame even 10 darks are quite enough,
– I have been trying different approaches but have not yet settled on
one (a huge number of darks collected over longer time vs 8-20 darks
collected after each imaging session), but in both cases the “Auto”
feature is great.Flats
====What
– records the uneven illumination of the image,
– dependent on the camera (sensor size and type) and the optical system
(scope, including barlow lenses, extension tubes etc),
– even filters can change it (usually not their color but their size
and position),
– dust in the sensor is also recorded.How
– use an evenly illuminated source of light (evening sky opposite the
setting sun, double T-shirt in front of the lens, a lightbox etc),
– preferably light should be bright enough to keep the exposure time
under one second (otherwise, stack more or blur the noise out),
– check that the scope/lens is focused to infinity (no need to be perfect
but should be very near),
– use the lowest sensitivity (usually ISO 100),
– use camera autoexposure (Av mode in Canon),
– take a few (4-10) and average-combine them,
– for lenses, one set for each aperture setting,
– for scopes, one set for each combination of filters/extension tubes/barlows
etc, in some cases even for different camera orientations,
– I prefer to keep the camera sensor clean – especially when taking
the flat frames, to get the dust out of the equation,
– the ImagesPlus from version 2.75 does not need changing flats into
grayscale any more, but other programs usually need that.Use
– whenever the optical chain is the same (scope, filters etc),
– some telescope/camera combinations “sag”, so you may need to make sure
the orientation is the same,
– for lenses use the one with the same aperture,
– keep the sensor clean also when imaging,
– I have taken four sky flats, rotated 90 degrees, for each lens and
aperture (upto 1 stop closed down for 10D, full frame cameras require
more) and averaged each set together.Bias
===What
– reflects the camera “zero” level,
– different for each pixel, usually has a pattern over the image area,
– camera-dependent,
– ISO sensitive,
– not dependent on optics.How
– cap the lens (or the camera without a lens),
– use the same ISO setting as for light frames,
– pick the shortest possible exposure,
– take a few (1-10) and average-combine them.Use
– usually not required, because unscaled dark-calibration subtracts
the bias as well,
– if you have a remaining weak fixed pattern all over the image, bias
frames may help,
– you can always reuse them when the ISO setting is the same (for the
same camera),
– I have taken one set (10 images for each ISO, average-combined) which
I use repeatedly.Dark and bias frames change slowly over the time, so you probably should
not use anything more than one year old.ParticipantThe weekly voting trend has been in a downward direction for months now, but particularly so in the last 4 contests, consecutively. What’s going on here? Any clue how fark.com’s traffic is, in general, else?
//edit: Ooof. Nevermind….
ParticipantElse; I really like the inner-pumpkin shot; very unique and original. Did you fit the camera in the pumpkin, or cut a hole into hit and shoot from behind?
ParticipantWell it’s prime trick or treating hours in most of the country so I’d guess that’s where people are. We’ll probably have a large amount of entries tomorrow.
*doh!*
//I have to work tonight. I forgot others get to play.
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