PIX 2015
Greg VdB

Greg VdB

Lives in Earth
Works as a Geoscientist
Has a website at www.pbase.com/gbleek
Joined on Sep 6, 2002

Comments

Total: 280, showing: 1 – 20
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On meteor shower challenge (9 comments in total)

For people reading the messages below: Mario and I have been exchanging more thoughts on this topic in the comments section of his photo.

Also, in case you want to see more meteor shower images, here's a great thread from the Astrophotography Talk Forum with results from the Perseids:
http://www.dpreview.com/forums/post/56310737

Direct link | Posted on Aug 31, 2015 at 18:52 UTC as 1st comment
On meteor shower challenge (9 comments in total)
In reply to:

Greg VdB: From the top 10, the "meteors" in the pictures that came 1st, 2nd, 4th, 6th, 7th, and 10th appear to be satellite trails. To make the distinction here are two easy tests:

1) In a series of images at short intervals (a few seconds at most), check the adjacent (prior and later) images for trails in the continuation of the one you hope to be a meteor trail. If you see such a trail (often across several frames), what you caught is CERTAINLY a satellite, since almost all meteors flare only for an instant.

2) most meteors burning up in the atmosphere go through different stages: first they gradually brighten, then they might "flare" (~explode) if they are particularly bright, and then they fade quickly. The recorded trail almost always reflects these stages, leading to an asymetric appearance. Satellites can also go through phases of brightening and dimming, sometimes within the time frame of a single exposure, but usually do so in a symmetric fashion.

(for people reading this: Mario and I have been exchanging more thoughts on this topic in the comments section of his photo)

Direct link | Posted on Aug 31, 2015 at 17:21 UTC
In reply to:

Greg VdB: As Zachary noted, none of these are trails from meteors, they are all satellite trails. Besides the difference in appearance (as Zachary describes), this is easily confirmed by looking at adjacent images, assuming you were taking a sequence of pictures with only 1 or 2 seconds between exposures.

Hi again Mario,

that timeframe also favours satellite trails, as the Perseid radiant is still low in the sky and the Sun not far under the horizon, illuminating many satellites. Doesn't mean Perseids don't appear yet (and I'm glad you saw some live!), but it makes it more likely that at least some of the trails you captured were made by satellites in that limited viewing and time frame. Sorry that I remain such a skeptic ;-)

Look here for a timelapse video I made showing the fireball and its subsequent trail: https://vimeo.com/126699070
Every frame is a 25s exposure, followed by a 2s gap before the next exposure (I always turn off in-camera noise reduction to maximize the time that my camera is collecting light, to miss the least amount of meteors possible). Hence I could calculate the total interval that the meteor trail was recorded - which is much longer than what I could see visiually, since the sensor at 25s and iso 5000 is much more sensitive than my eyesight.

regards,
Greg.

Direct link | Posted on Aug 31, 2015 at 17:18 UTC
In reply to:

Greg VdB: As Zachary noted, none of these are trails from meteors, they are all satellite trails. Besides the difference in appearance (as Zachary describes), this is easily confirmed by looking at adjacent images, assuming you were taking a sequence of pictures with only 1 or 2 seconds between exposures.

The above criteria suggest sattelite trails to me. However, I'm just one person, and realize very well that I'm not always correct. In case you would like a third, fourth, and more opinion, I would suggest to head over to the Astrophotography Talk Forum and run it by the very kind people there.

Three questions:

1) did I understand correctly that you took only eight frames? (If so, I am certain that at least the majority of what you captured are satellites, since even on peak night, one would not observe that many meteors over such a short period in such a small portion of the sky)

2) At what time did you take the photos? (important to know if satellites would have been reflecting sunlight)

3) Did you align the pictures before copying the trails to the background frame?

Again, thanks for taking the time to respond. And I hope that soon you'll be lucky enough to capture a fireball like this - no ambiguity then! ;-) http://www.pbase.com/gbleek/image/159932258

regards,
Greg.

Direct link | Posted on Aug 31, 2015 at 12:36 UTC
In reply to:

Greg VdB: As Zachary noted, none of these are trails from meteors, they are all satellite trails. Besides the difference in appearance (as Zachary describes), this is easily confirmed by looking at adjacent images, assuming you were taking a sequence of pictures with only 1 or 2 seconds between exposures.

Dear Mario, thanks for entering into a conversation about this - many people would not, and I appreciate it.

First I wish to note that I fully agree that astrophotography is indeed for a large part about post-processing. With meteors, often we're forced to "push" their brightness in post, like I did here (also see the photo caption): http://www.pbase.com/gbleek/image/157062283/original Note that despite increasing their brightness, they retained their typical "pointed" shape.

From the un- (or less-) processed frames in your gallery, I am still sure that most if not all of what you captured are satellite trails. The original one in the background frame looks a bit meteor-like at the top end, but I fear this results from the vignetting of your lens. The bottom end has the typical appearance of a satellite trail cut off by the shutter, which, to my eyes, is also true for the other trails. Your trails are also suspicially narrow and maintain their widths over long distances.

Direct link | Posted on Aug 31, 2015 at 12:24 UTC
On Milky Way with Meteor in the meteor shower challenge (2 comments in total)

Very impressive Jonathan. Did you see it live? Must have been quite the sight!

Direct link | Posted on Aug 30, 2015 at 13:25 UTC as 1st comment | 1 reply
In reply to:

Greg VdB: As Zachary noted, none of these are trails from meteors, they are all satellite trails. Besides the difference in appearance (as Zachary describes), this is easily confirmed by looking at adjacent images, assuming you were taking a sequence of pictures with only 1 or 2 seconds between exposures.

That "radiant" lies to the opposite side of Andromeda to be the Perseid one... This in itself doesn't mean one or more of the trails couldn't be meteors (Perseid or otherwise), but they don't look like it at all. Compare for instance with the image that came fifth, showing a lot of meteor trails (not all Perseids) and an idea of where the shower's radiant is situated.

Btw, I don't want to cause offense - just trying to make people aware of a mistake that is very easy to make (I surely made it myself when I just started out).

Direct link | Posted on Aug 30, 2015 at 13:15 UTC
On Pure Greatness in the meteor shower challenge (1 comment in total)

Impressive that you got the MW so nicely from your light-poluted area, Rutger! The image is a bit small to be sure, but I assume the trail at the right is a satellite, and the big one on the left a Perseid? Did you see it live? Must have been a stunner!

Direct link | Posted on Aug 30, 2015 at 08:35 UTC as 1st comment
On meteor shower challenge (9 comments in total)
In reply to:

Greg VdB: From the top 10, the "meteors" in the pictures that came 1st, 2nd, 4th, 6th, 7th, and 10th appear to be satellite trails. To make the distinction here are two easy tests:

1) In a series of images at short intervals (a few seconds at most), check the adjacent (prior and later) images for trails in the continuation of the one you hope to be a meteor trail. If you see such a trail (often across several frames), what you caught is CERTAINLY a satellite, since almost all meteors flare only for an instant.

2) most meteors burning up in the atmosphere go through different stages: first they gradually brighten, then they might "flare" (~explode) if they are particularly bright, and then they fade quickly. The recorded trail almost always reflects these stages, leading to an asymetric appearance. Satellites can also go through phases of brightening and dimming, sometimes within the time frame of a single exposure, but usually do so in a symmetric fashion.

Btw, in case you are a novice and want to delve further into nightsky photography, I can highly recommend the Astrophotography Forum here on DPR!

Direct link | Posted on Aug 30, 2015 at 08:32 UTC
On meteor shower challenge (9 comments in total)

From the top 10, the "meteors" in the pictures that came 1st, 2nd, 4th, 6th, 7th, and 10th appear to be satellite trails. To make the distinction here are two easy tests:

1) In a series of images at short intervals (a few seconds at most), check the adjacent (prior and later) images for trails in the continuation of the one you hope to be a meteor trail. If you see such a trail (often across several frames), what you caught is CERTAINLY a satellite, since almost all meteors flare only for an instant.

2) most meteors burning up in the atmosphere go through different stages: first they gradually brighten, then they might "flare" (~explode) if they are particularly bright, and then they fade quickly. The recorded trail almost always reflects these stages, leading to an asymetric appearance. Satellites can also go through phases of brightening and dimming, sometimes within the time frame of a single exposure, but usually do so in a symmetric fashion.

Direct link | Posted on Aug 30, 2015 at 08:30 UTC as 2nd comment | 6 replies
On Perseids Meteor Shower 2015 Composite Image in the meteor shower challenge (1 comment in total)

Nice one Jack! Since the pictures voted in 1st, 2nd, and (probably) 4th position contain only satellite trails, you got the silver medal ;-)

Direct link | Posted on Aug 30, 2015 at 08:05 UTC as 1st comment

As Zachary noted, none of these are trails from meteors, they are all satellite trails. Besides the difference in appearance (as Zachary describes), this is easily confirmed by looking at adjacent images, assuming you were taking a sequence of pictures with only 1 or 2 seconds between exposures.

Direct link | Posted on Aug 30, 2015 at 08:01 UTC as 3rd comment | 10 replies
In reply to:

JanMatthys: Ahem....it's and F/2.0 lens, why would all of your samples be in daylight? Not a single indoor low-light? geez

Good to know Rishi, thanks! And FYI, my own results on the starry sky correspond very well with the lab-based test results of Lenstip, so you don't necessarily have to shoot on one of the two nights a year of clear skies in the Seattle area ;)

Good reply Barney - years and years of practice...

Direct link | Posted on Jul 22, 2015 at 18:38 UTC
In reply to:

JanMatthys: Ahem....it's and F/2.0 lens, why would all of your samples be in daylight? Not a single indoor low-light? geez

In essence I agree on the iso part, Barney, though it *would* be interesting to have some samples of nighttime street photography to see how the lens deals with flare/ghosting in such situations. Also, as my pet interest, I'd love to see a series of shots at different apertures of the Milky Way to see how lenses handle coma.

Direct link | Posted on Jul 22, 2015 at 17:02 UTC

Even neglecting the score of posts about the shameful copying of someone else's work, this garnered significantly more comments than regular portfolio posts. Which underlines the quality of the original work by Joel Robinson!

Now, DPR, give credit where credit is due.

Direct link | Posted on Jul 20, 2015 at 06:07 UTC as 9th comment | 1 reply
On Pentax K-3 II added to studio test scene comparison article (177 comments in total)
In reply to:

starjedi: Interesting. I saw Pixel shift + K3II easily beats D810!!!

Badi, as a budding astrophotographer I have often stacked images to improve the S/N ratio, so I definitely agree on its usefulness! Maybe you are familiar with it, but if you ever want to give astrophotography a go, this is a free software I can highly recommend: http://deepskystacker.free.fr/english/index.html Doesn't work for scenes with a terrestrial foreground, though, so in that case I also use median stacking in PS, following this tutorial: http://www.lonelyspeck.com/stacking-noise-reduction/

Direct link | Posted on Jul 17, 2015 at 08:46 UTC
On Pentax K-3 II added to studio test scene comparison article (177 comments in total)
In reply to:

starjedi: Interesting. I saw Pixel shift + K3II easily beats D810!!!

Here's a good article about super-resolution: http://petapixel.com/2015/02/21/a-practical-guide-to-creating-superresolution-photos-with-photoshop/

Direct link | Posted on Jul 17, 2015 at 08:07 UTC

Nice post, Rishi. I am glad that you keep up the pressure like this. As a Canon user that seems obvious, but here's hoping that Sony takes note as well - they've got a big lead now, but for it to stay like this, they can't rest on their laurels either, no matter what the "5-year-old-sensor-tech" crowd may believe.

Direct link | Posted on Jul 10, 2015 at 07:54 UTC as 64th comment
In reply to:

J A C S: 1. Very misleading graph (the 1st one). The vertical axis should start from 0.

2. "DxO does something similar in their 'Print' mode display of their data; however, that levels the playing field a bit much to an output of 8MP, [...]"

It does not. They show 2.4 EV difference at 8mp, you compute 2.5.

Totally with you, Rishi: with no deviating trend or data cluster below 6.5, there's absolutely no reason to display anything below. I've always thought that a break-in-axis is only used to display data that clusters at two (or more) distinctively different values, not when zooming in on the region where *all* data occurs. In the figure above, all necessary information is there - it's up to the viewer to properly read the graph by taking note of the axes values... Of course, I'm just a lowly geoscientist, and we are famously bad at maths.

Direct link | Posted on Jul 10, 2015 at 07:39 UTC

Seems like an amazing piece of kit for the money. With manual aperture, macro, and tilt, this looks like it could be an instant classic for timelapse purposes! The f/4 maximum aperture limits it somewhat for astro(-timelapse) work, but with sensors getting ever better, this limitation isn't that great either. Very eager to see it's astigmatism performance in that sense... And flare against bright light. Anyway, from the "reviews" so far, to me this looks like a grown-up lensbaby.

Direct link | Posted on Jun 24, 2015 at 02:46 UTC as 31st comment
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