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Posts for: bobwalder
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Aug 21, 2017 10:48:09   #
CPR wrote:
Display on a computer screen.................


How many computer screens will I need to fill my 16x12' wall space? What is the best way to hang them? How can I hang them without the power cords being visible? Can I drive 12 screens from one computer with a different image on each, or will I need a computer for each one? Where will I put the computer so that it is not visible? How can I run connections from computer to screen without wires being visible? I prefer borderless presentation.... how do I get rid of that nasty surround from the computer screen? I prefer flat to the wall presentation, will I need to dig into the sheetrock to make the front of the screen flush with the wall? How easy will it be to adjust the position or orientation of those when I rotate my pictures?

And... how much will that all cost me? I am thinking there will be a fair few screens needed for that 16x12' space. Oh, and I would like a mixture of sizes too, from 20x16" down to maybe 10x8"

I absolutely LOVE your idea of using a computer screen to display artwork on my walls instead of boring old canvas or paper.... if you can help me with some of the practical issues mentioned above I would be most grateful....
 
Aug 14, 2017 14:09:19   #
LoneRangeFinder wrote:
I realize there's a sub forum for this but most posts are several years old.
So question: any recommendations based on experience for a digital camera appropriate for snorkeling in Hawaii? Olympus TG-3 seems to be a contender....

I'd rather not get into Ikelite housings for full sized digital cameras...

Thanks


Just bought the Olympus TG-5 for my Florida vacation - more than happy with the capabilities and quality (4K video and RAW images were top of my list). Used it on beach, underwater in sea, pool, lake - works great. Get one of those cheap "floater" wrists straps for it... I just leave mine floating on the surface of the pool 'til I need it :)
Jul 21, 2017 11:41:47   #
SS319 wrote:
You know, all those places you listed prohibit drones....


I am pretty sure that is the point of his post!!!
Jun 15, 2017 12:50:54   #
jmcgloth wrote:
Sheesh! "they're fair game..."


LOL.... annoying, isn't it?
Jun 6, 2017 11:14:21   #
Mac wrote:
The newer processor will move the photo to the memory card faster, but have no effect on low light capabilities.
The difference between 16MP and 12MP is minimal and if anything the 12MP will be better in low light and color rendition because the pixels will be larger.
The TG-5 has improved ergonomics and better button placement than the TG-4.


Thank you Mac... that helps...
Jun 6, 2017 08:48:28   #
Looking for a good rugged waterproof camera that will shoot RAW... The TG-4 seemed to fit the bill. But the new TG-5 is out this month and it has 4K video and the newer processor (better low light?)

BUT - resolution goes DOWN from 16MP to 12MP

Why? Any thoughts on which would be best for general use/underwater/etc.? Will that 4MP make a significant difference when set against the benefits of the newer processor, faster burst speeds and 4K video?

BTW - I know some of you don't see the point of 4K video - would rather we didn't go down that road on this thread thanks... let's just assume here that $K is "better" than 1080P for my purposes.
 
Jun 1, 2017 19:59:50   #
JimH123 wrote:

To do this stacking, there is a free application called 'DSS' which stands for Deep Sky Stacker. I suggest only downloading from the actual site since there is no guarantee how clean a program is coming from some other URL: http://deepskystacker.free.fr/english/download.htm.


Dammit.... Windows only! :o(
Jun 1, 2017 18:29:24   #
JimH123 wrote:
That's the beauty of stacking. It aligns each image so that all the stars line up on top of each other. And I used 4 sec only because I wanted to preserve star colors. When you expose for too long a time, all the bright stars saturate and as saturated stars, they all appear white. If I can expose for a shorter period of time, the color can still be seen. Now the advantages are stacking are that the stars become more distinct and the background appears darker due to an increase in the signal to noise ratio of the image being made up of additional images. But the big thing is that noise goes down too. For any given image, there will be noise. On the next image, there is noise too, but the random placement of the noise means that they noise specs don't line up in exactly the same pixel positions. And as you add more and more images, the image quality goes up as the noise goes down.

To do this stacking, there is a free application called 'DSS' which stands for Deep Sky Stacker. I suggest only downloading from the actual site since there is no guarantee how clean a program is coming from some other URL: http://deepskystacker.free.fr/english/download.htm.

There are a ton of settings in DSS, but the settings all have a default and for the majority of things you might do, the default settings are fine. I also like to add 'Darks' which means that I just capture some additional images with the lens cap on, but same camera settings. What it does now is to locate the stuck at pixels and DSS uses that information to fix the DSS output so that these stuck pixels don't show up in the final result.

After DSS runs, it creates a file called 'autosave.tif'. I don't do any additional adjustment within DSS and go straight to Photoshop to stretch the 'autosave.tif' file. First thing to do is to go to adjustments and change 'mode' from 32-bits to 16-bits. And then I do 'curves' and then 'levels', perhaps over and over until I get the result I want. I also use a plug-in from RC-Astro called XGradient to make the sky be a consistant dark color.

I use version 3.3.4 and find that the next earlier version doesn't support my cameras.

Some of my efforts are done with telescopes, and some with cameras and camera lenses. Just to show that I may use a longer shutter time, I am attaching the results of a stack of 15 + 10 darks using an Olympus em5ii and a 400mm f5.6 old m42 Pentax lens. This gives an effective focal length of 800mm, but is useful to see what focal length is needed to see galaxies. But some are closer and some are farther away, so you see all types. This one is 15 images of 60sec each with ISO 1600.

And just for fun, an image of Markarian's chain which shows a ton of galaxies. With the 400mm lens (effective 800mm), you can see about 15 galaxies, but a bigger scope sees far more.

Finally what can be seen using a telescope. The scope has a longer focal length, and the camera is a CCD camera (Atik Infinity), and you get image #3. This was a 40 sec image stacked 40 times.

Hope this explains a few things.
That's the beauty of stacking. It aligns each ima... (show quote)


Awesome stuff - thanks Jim
Jun 1, 2017 16:23:37   #
JimH123 wrote:
I am adding a picture I took tonight using a 14mm f2.8 Rokinon lens on an Olympus EM5ii. This is a 2.0x crop type camera, so this is effectively the same FOV as a 28mm on a Full Frame. It is too early in the season for the Milky Way as that will be overhead in a couple more months. And at this focal length, not much to see in the way of galaxies. And no nebula either. But there are certainly stars to capture. I used a 4 sec shutter speed, ISO 1250 and f2.8. Also stacked 35 images, plus 10 darks to detect and remove stuck pixels. Since the dimmer stars tend to twinkle, the act of stacking tends to make them more distinct.

One thought on this: I started tonight with the Olympus 14-40 f2.8 pro lens. It is certainly sharp enough to do stars. But it uses focus by wire. My experience with focus by wire when doing stars is that it is absolutely frustrating. After not achieving good focus, decided to switch to the Rokinon 14mm f2.8 lens which is 100% manual, and suddenly focus was so easy to do. I was using Olympus Capture using a USB interface and the live view of the camera was then displayed on my laptop. Magnified 10x and then adjusted focus. A bright star first reached the smallest size. And then some faint stars started to appear and adjusted them for max brightness.

Then I started a time lapse and had it shoot a 4 sec image once every 10 sec. After 35 images, decided I had enough and then captured 10 dark frames (same shutter time and ISO), and put the lens cap on the lens. Stuck pixels are caught by this process.

After stacking with DSS, the image needs to be stretched to increase the brightness of the stars and to darken the sky using Photoshop. Once done in Photoshop, sent to Lightroom where contrast is increased, and noise removed.

Anyway, this should give you an idea of what can be captured and give you something to shoot for.
I am adding a picture I took tonight using a 14mm ... (show quote)


Thanks Jim.... can you explain what you mean by "stacking" please? How come such short exposures? Also wouldn't time lapse result in trails or indistinct or even multiple points for each star?
Jun 1, 2017 16:21:34   #
mjmoore17 wrote:
I have found the Canon 6D to be a very good camera for the use that you described. Here is an example of Milky Way with 6D and a Canon 2.8 lens.


Beautiful image. Can you give me the focal length, ISO and exposure details?
May 31, 2017 14:22:57   #
JimH123 wrote:
Stars are point sources of light, and the f-stop value has less impact on the brightness of a star than does the area of the aperture. A 11mm at f4 has an aperture of 2.75mm. A 20mm at f4 has an aperture of 5mm. Same f-stop value, but larger aperture on the 20mm, and the stars will be brighter. This why telescopes keep being made larger and larger. If you compare the areas, you can compute the difference.

In the case of a terrestrial view, the f4 on both lens will create an image of similar brightness.
Stars are point sources of light, and the f-stop v... (show quote)


Again... I think this is the salient point here... and something that I simply did not understand until now. Thank you for this, Jim!!!

I will, of course, still go out and do the comparison testing!!! LOL
 
May 31, 2017 12:23:28   #
JimH123 wrote:
This is the problem then. You cannot treat stars like terrestrial objects where everything within a range appears to be in focus. Stars require EXACT focus, or they go away. This is what you need to practice on. Not all cameras are equal when it comes to focusing on stars. I shoot Sony and Olympus and they are rather easy to get good star focus. But I have known Canon shooters that really struggled to see the dimmer stars for focus.

Start with a longer FL lens and practice your focus so you can see the stars. Even a 50mm will allow you to go for a few seconds without star trails, but the stars will be easier to see. But master that focusing, and then repeat, and you will have better success.

And one more thought. Some lenses don't actually go all the way to infinity. In the case of a wide angle lens, this is not likely to impact terrestrial images. But for stars, it can be a disaster, since they will not tolerate the slight focus error. You will need live view, focus magnifier at max, and a wide open aperture to check it out.

Also, wide angle lenses do not gather much light. A 20mm lens at f2.8 captures light with a 7.14mm objective. A 20mm lens at f4 is only a 5mm objective. This means that it captures 1/2 as much light. Now you lens is 11-14mm at f4. When at 11mm, the objective is 2.75mm. This is about 1/7 the amount of light as the 20mm f2.8. And this is also part of the problem of using wide angle lenses. I have done some panoramas using a longer lens and creating a wide angle effect and it works well considering how much additional light it gives you to work with. For example, a 50mm f1.4 uses an apterture of 35.7mm. Compared to the 11mm f4, it is gathering 169 times as much light! Plus, it is easier to focus.
This is the problem then. You cannot treat stars ... (show quote)


Now THAT is REALLY interesting.... and that might explain a lot given that he was using something like a 16mm or 20mm at f2.8, and I was using an 11mm at f4

Just to put the focus issue to bed - I was very happy with focus on the final images....
May 31, 2017 11:36:22   #
JimH123 wrote:
How good of focus did you have on the stars? When photographing stars, the intensity drops off rapidly as it falls out of focus. You can see this easily in that the stars become fatter as they move out of focus and the same amount of light is spread over this larger area.

When I focus on stars, I use the focus magnifier and do a focus on a brighter star. But I watch carefully for dimmer stars to come into view. Once I see dimmer stars, I concentrate only on a dim star and adjust for max brightness.

You are also using a very wide angle lens and it is difficult to even see the stars with wide angle, but it still has to be done. Focus has to be perfect to see lots of stars.
How good of focus did you have on the stars? When... (show quote)


Thanks for that. 11mm lens focused on slightly less than infinity gave me everything from around 3ft to infinity in focus. I also tried focusing on infinity... did not actually try to focus on stars specifically... was almost impossible to see them in VF
May 31, 2017 11:34:20   #
PGHphoto wrote:
If you were basing the results on the camera viewfinder, without seeing a print or viewing it on a full size monitor, it could be simply they had their viewfinder brightness turned up. I do not have a 6D but have shot astro on a 70D and taken very good shots at less than 1600 ISO under 30 seconds with a 2.8 aperture. You really should use 30 seconds as an absolute max shutter due to the rotation of the earth causing star trails at longer intervals. A friend with a 6D has not seen the issues you describe.

I am assuming you were shooting manual exposure during light painting attempt ?

Good luck identifying the problem and let us know what you find
If you were basing the results on the camera viewf... (show quote)


Thanks. I do think that he had his viewfinder turned up brighter than mine for sure, but final results on computer monitor were also strikingly different. With 11mm focal length 40-45 secs is acceptable without seeing trails. I did try bumping ISO even higher to get same 20 sec exposure they were using, BUT even by doubling ISO again I was still looking at closer to 25-30 seconds for equivalent results compared to their 20 secs.... truly weird....

Note that the situation you just quote - 1600ISO, under 30 seconds, f2.8 - is pretty much what I was seeing from the others. What I did was double the ISO to 3200 in an attempt to use same 20 sec exposure at f4.... didn't work... had to increase to 45 secs... so I was exposing for double the time as the others.

Need to check that lens is not stuck at f5.6... or camera/lens communications are broken somehow...
May 31, 2017 11:19:41   #
SS319 wrote:
Scientists do not typically change two variables on the same test run. Match all settings between cameras.
.


I made a career out of testing complex computer security devices... believe me when I tell you I know how to test stuff.... ;o)

Good idea re astronomy club... but I can't really wait for that given short return window on this equipment....
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