PF Photography: Tips, Tricks, & Photo Sharing

[Andre]

I generally shoot astronomical and near-earth objects (satellites, etc) with a fully open aperture. It helps that the weather is cooler now, the camera noise is noticeably lower and the sky seems darker as well.

Maybe consider looking at the sweet spot idea.

That's the reason why I basically avoid full open aperture unless required for available light or bokeh. Most of the time, generally speaking, you hit the sweet spot, stopped down about two clicks and before diffusion sets in, giving a rather tight range for best aperture. 5.6 is a magic number.

 

[amal]

How do you find this one?

 

[Andy Resnick]

Maybe consider looking at the sweet spot idea.

That's the reason why I basically avoid full open aperture unless required for available light or bokeh. Most of the time, generally speaking, you hit the sweet spot, stopped down about two clicks and before diffusion sets in, giving a rather tight range for best aperture. 5.6 is a magic number.

It is true that aberrations (except distortion) decrease with decreasing aperture. But sometimes I need the biggest 'light bucket' I can get.

 

[navynuclear]

A path through the woods near my house.

 

[NileQueen]

Very picturesque.

 

[NileQueen]

Amal, I like yours too.

 

[AlephZero]

A question about image gathering from satellites in LEO, as used on Google Maps etc.

This is prompted by PF thread about a research paper where data about animals (cows and deer) was derived from images on Google Maps, and the paper claimed surprising (and not obviously believable) results.

Just for fun I looked at some Google Maps images of an area that I know well on the ground, which should have contained shown plenty of fields with cows and sheep - except there were virtually no animals visible on the images, and the few that were there (about 1% of the number I expected to see) were very blurred. Also there were also no vehicles on any of the roads, which is very improbable. (Cars that were obviously parked, near buildings etc, were clearly visible)

There was no problem about the image resolution at the highest zoom level (e.g. white painted road markings and even overhead power cables were clearly resolved), so I wonder if there is something about the image gathering technology which can't resolve moving objects, or filters them out. Long exposure times, because of the extreme telephoto lenses, for example? I couldn't find anything relevant the Web.

I'm specifically asking about satellite images here. Apparently in urbanized areas aerial photography is often used to give better resolution, and that does show road traffic, etc.

 

[Borek]

Just for fun I looked at some Google Maps images of an area that I know well on the ground, which should have contained shown plenty of fields with cows and sheep - except there were virtually no animals visible on the images, and the few that were there (about 1% of the number I expected to see) were very blurred. Also there were also no vehicles on any of the roads, which is very improbable. (Cars that were obviously parked, near buildings etc, were clearly visible)

I doubt there is plenty of time to take these pictures - after all, these satellites are rather low and fast. Usually I see plenty of cars - perhaps pictures were taken early, like 5 a.m., before the traffic started?

But then perhaps pictures are taken in some counterintuitive way (three line sensors using the same lenses?) and then postprocessed to get rid of artifacts of the moving objects? Just guessing here.

 

[AlephZero]

I doubt there is plenty of time to take these pictures - after all, these satellites are rather low and fast. Usually I see plenty of cars - perhaps pictures were taken early, like 5 a.m., before the traffic started?

Some images were clearly in sunlight with the sun high in the sky. From the farming activity visible they were probably taken in June. So I don't think the time of day explains the lack of road traffic.

 

[Andy Resnick]

I'm specifically asking about satellite images here. Apparently in urbanized areas aerial photography is often used to give better resolution, and that does show road traffic, etc.

Interesting... I never thought about this, but looking at NYC, around Times Square, using Google maps and Terraserver shows very few cars and people- much fewer than I would expect. The problem is not acquisition times- there are cars driving and people walking. The images may have been taken at odd times of day, but the shadows all seem to indicate 'normal' times.

Since the maps are generated based on many images, perhaps the images are chosen specifically to minimize the number of people/animals- images acquired in winter, for example?

 

[Andre]

Looked around a bit in my area, no traffic jams but certainly a lot of traffic at certain places.

Keep in mind that the orbits of these (this) satellite is rather rigid. So it can only make a picture of a certain area at a certain time and the next picture weeks? months? later. Then it's visible light, so there must be no clouds. For some area's that's very rare, but the least amount of clouds are in the early morning shortly after sun rise, before convection kicks into produce cumulus clouds.

So I can imagine that having a decent picture of certain areas is a tough job in the first place, and the amount of traffic would hardly be a selection factor. Maybe that summer pictures made at something like 5-6 am, minimizing clouds, are more often successful. Probably not a lot of activity then.

 

[AlephZero]

The lack of traffic is a bit of a side issue, but it struck me as being rather odd. The "invisible sheep" would have been in the fields at any time of day or night. Granted some of the cows might be out of sight being milked in early morning and evening, though.

 

[Borek]

Wow: a year long exposure using pinhole camera.

 

[fuzzyfelt]

Wow: a year long exposure using pinhole camera.

Wow!

 

[Andy Resnick]

Wow: a year long exposure using pinhole camera.

very cool!

 

[amal]

Amazing. The photo's too good.

 

[Andre]

Relatively cold here with a strong easterly wind do curious things to reed sticks at the lake before the water freezes over:

This is straight from the camera:

http://dl.dropbox.com/u/22026080/Natural%20ice%20sculpture_1.jpg

after some tone mapping and cropping:

http://dl.dropbox.com/u/22026080/Natural%20ice%20sculpture_.jpg

Edit: Same spot looking in another direction:

http://dl.dropbox.com/u/22026080/Natural%20ice%20sculpture2.jpg

 

[Andy Resnick]

Maybe it's not photography exactly, but my lab class is making holograms this month, using a kit (http://litiholo.com/). I had no idea how well the kit would work, but the students made some really nice holograms and enjoyed the process, so I thought I'd give it a try myself. I decided to try making a hologram of a computer chip:

http://img42.imageshack.us/img42/7021/dsc1626.png

Here's the hologram of the 'bare' chip:

http://img821.imageshack.us/img821/4233/dsc4757.png

It's *really* bright- I had to use a polarizer to cut the intensity down enough to take a photo. The next step was to make a hologram of the chip as viewed through a microscope objective:

http://img217.imageshack.us/img217/8514/dsc4741.png

And here's the result:

http://img85.imageshack.us/img85/4986/dsc47681.png

Not bad for a toy kit!

 

[Andy Resnick]

Here's my final hologram:

http://img192.imageshack.us/img192/1710/63mm2.jpg

The object is a computer chip, magnified with a 63mm Luminar. The holographic plate was placed near the back pupil plane, producing a virtual image at infinity. This image was taken with a 85/1.4, and since the virtual image is far away, the optics table etc. is out of focus.

There's quite a bit of optics involved with doing something like this- very non-trivial.

 

[Andy Resnick]

Today was the second half of an experiment- a professor from the Art department gave a special demo to my class. He turned a colleagues room into a camera (a camera obscura). It's really cool. Here's a couple images showing downtown Cleve-o, looking north to Lake Erie:

http://img252.imageshack.us/img252/8986/dsc93241filtered.jpg

http://img687.imageshack.us/img687/8324/dsc93251small.jpg

 

[fuzzyfelt]

Very nice!

 

[Andy Resnick]

Got some excellent shots of the ISS (space station) during tonight's flyover. Easy-breezy: I set the exposure by Venus (magnitude -4.7 vs. ISS @ -2.4, so I doubled the ISO to compensate) 800/5.6, 1/500s ISO 250, no mirror lockup. Trivial to track- I took about 120 shots over 5 minutes. My card reader is at work, so I'll post a montage ASAP.

 

[Andy Resnick]

Here's the whole series, no processing other than cropping and white/black levels. Seeing conditions were... "not optimal". ISS came into view from the NW and traveled approximately at a constant 40 degree elevation angle down to the SE.

http://img407.imageshack.us/img407/4131/montaget.jpg

The moral of the story is: 1) *fast* shutter speeds are essential. 2) mirror lockup isn't needed, and 3) a good tripod head is required. Even though I was only slewing at ~ 3 degrees/second, I could not have done this without a gimbaled mount- I was tracking with one hand and remote triggering the camera with the other.

 

[Andy Resnick]

Here's a cleaner version- I individually adjusted each frame and deleted the 21 worst:

http://img851.imageshack.us/img851/7452/montagegoodsmall.png

I can see how the ISS rotates as it passes; it starts out with the bright main truss on the backside, and then rotates into front view. It also appears that the station is executing a roll maneuver (with respect to me) during the pass, but that could be my imagination.

Here are some external timelapse videos from a camera mounted to the ISS with some hints as to what is moving when:

 

[Andre]

So just I got myself a http://www.sigmaphoto.com/shop/150-500mm-f5-63-apo-dg-os-hsm-sigma today. I did quite an elaborate research with on the shortlist also the Canon 100-400L (Turbo's lens) and the Canon 400mm F5.6L.

The Sigma won finally, due to the extended reach. As 400mm is hardly much of a gain compared to the 70-300. Maybe with tele extenders on the 400mm L, which has sufficient image quality for that, but it lacks the image stabilization.

I accepted the caveats of the Sigma, the weight and the soft image at full opening at maximum range. I tested that sort of randomly -not prepared- on these little bottles:

Oops, I did not spot that little dead bug at the time. I should have dusted first

But indeed it's soft full open as seen on this 100% crop on top:

But the bottom crop at F10 is pleasing enough to keep it. I think.

 

[Topher925]

That is one helluva lens. I was looking at buying a nice 400 or 500mm prime not to long ago for nature photography but couldn't bring myself to fork out that much dough so I bought a telescope and adapter instead (Orion ST80). Surprisingly good images for a hundred bucks but big, heavy, and difficult to use so now its only used for astrophotography.

I did recently get a sweet deal for a Pentax DA 70mm Limited. And while it doesn't have the reach of 500mm, 70mm is still not bad and its ridiculously sharp at f5.6 and beyond. Its so small and light it fits in my shirt pocket.

A shot with the 70mm at f2.4 ISO 200

100% Crop of above image

 

[Andy Resnick]

So just I got myself a http://www.sigmaphoto.com/shop/150-500mm-f5-63-apo-dg-os-hsm-sigma today. <snip>

<snip>
I did recently get a sweet deal for a Pentax DA 70mm Limited. And while it doesn't have the reach of 500mm, 70mm is still not bad and its ridiculously sharp at f5.6 and beyond. Its so small and light it fits in my shirt pocket.
<snip>

Yay! new toys! I put in for a new lens as well, we'll see how it does when I get it.

 

[Ms Music]

So just I got myself a http://www.sigmaphoto.com/shop/150-500mm-f5-63-apo-dg-os-hsm-sigma today.

I think I have that same lens, if not, one very similar. I may have to drag it out and play around with it and try to copy some of the stuff you do. I have barely touched it, but never was satisfied with its performance. And I didn't have the time to research it. I have always felt that A/ it doesn't work right, B/ my tripod isn't beefy enough for it, or C/ I too stoopid to use it correctly. I believe the correct answer is probably C.

Would you be willing to walk me through copying a few of your photos to see if I can truly eliminate option A and B?

 

[Andre]

Sure, happy to help out. I'll link to full size pix later today.

http://www.sigmaphoto.com/shop/telephoto-zoom-lenses and http://www.sigmaphoto.com/shop/telephoto-zoom-lenses?page=2 is the full line up of the long sigma's.

Obviously there are many reasons why the results may disappoint, then again you cannot expect the same quality from a budget 1K lens than the 10k lenses, especially the Canon 400mm II F2.8L is flat out sensational, but way to expensive for common sense. So I wasn't expecting a better result than the second crop in my previous post.

Anyway, compared to the result with the 100mm macro, there is still clearly quite some difference in quality.

the Sigma:

To elimate any possible factor that may degrade the picture, these were all made from a sturdy tripod obviously, Optical Stabilator off, and manual focus in life view, in which I can blow up the focus area. Then from life view (and hence locked up mirror) the picture is made using remote control, but a self timer would also work, elimating any vibration.

 

[Andy Resnick]

Interesting- is it just me, or is the color rendition different between the macro and tele? The 100mm seems to be more blue.