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Messages - noisejammer

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16
EOS Bodies / Re: Moving sensor: an attractive option?
« on: February 15, 2014, 05:19:38 PM »
Interesting application but dithering has been used to suppress digitisation artefacts in astrophotography for years.

The pixels on this sensor are 6.0 microns on a side. Implicit in this is the requirement that the lenses can resolve acceptably to pixel level.... something like a 8 micron spot. Since this translates to MTF50 of ~125 lp/mm, I am sceptical about the technique being of much value. Of course, it's possible to apply sharpening algorithms and there is information to work on.

Secondly, if anything is to be achieved, critical focus will be essential. Some sort of f/8 tilt shift lens might work here.

Third, it does require the tripod to be astonishingly stiff. Assuming an 80mm lens, the pixels subtend .006/80 radians = 15.6 arcsec. Achieving acceptable results probably needs the camera to be static at the scale of ~5 arcsec. This is achievable but considerable care is needed.

On the whole, 16 Mp is enough for me...

17
A lot depends on what you're trying to photograph, how much background light it present and how bright your strobe is.

If you can set the shot up so the cameras are in the dark, the obvious way is to open both apertures and then fire the strobe. If you do this, your images can easily be synchronised to less than a millisecond. Don't control the strobe with either camera - you can use the strobe's light measurement to get the exposure about right

If this isn't practical then you need to define how closely you want the exposure to be fired because the 5D2 and 7D have different delays when you trip the shutter. It certainly helps if you can set the cameras to the same exposure (trade off ISO against f-stop) and run everything in manual mode. You can then use a wired connection and put them in parallel (I think this will work if they are wired together but - some electrical buffering would probably be better.)

Another random thought - if you have an ultra-fast strobe (say a Q-switched laser), don't forget that light travels at a finite speed - this can make a difference. You need to get the distance to the subject the same for all the cameras.

18
Lenses / Re: Ken Rockwell reviews canon 50mm f/1.0
« on: November 22, 2013, 12:47:42 PM »
Other's have commented (and my tests have confirmed) that my 1D4 and 5D2 cannot actually see light from a cone that's faster than f/1.6.

This is incorrect. There is a loss of light due to the sensor but there is a definitively different blur with f/1.2 vs f/1.4 and f/1.6.


Pi - Ok I'll bite.

We seem to agree that many digital cameras are insensitive to light arriving from large apertures. I know this to be a fact with my 5D2 and 1D4 and all the f/1.2 and f/1.4 lenses I've tested. I invite you to test this if you disagree.

Nevertheless, you have a persistent belief that apertures wider than about f/1.4 decrease the depth of field even though very little additional light reaches the photodiode.

I would like to understand how a camera's photodiode can simultaneously detect and not detect light. It is a very clever trick. ;)

19
Lenses / Re: Ken Rockwell reviews canon 50mm f/1.0
« on: November 22, 2013, 08:36:50 AM »
Ah - another insightful rant from Clueless Kenny, the uber math whiz.
I'm quite curious how f/1.0 can be 1/2 to 2/3 stop faster than f/1.2... what causes it to vary? Phase of the moon?

Comparing the entrance pupils, the ratio must be (1.2)^2 = 1.44. In terms of stops that's 0.52. Ok, so it's half a stop faster than f/1.2 ....

But it's only half a stop better if the camera detects the light. Other's have commented (and my tests have confirmed) that my 1D4 and 5D2 cannot actually see light from a cone that's faster than f/1.6. This does vary from lens to lens - some modern lenses are telecentric so that all the light gets to the photodiode. However, the 50/1.0 comes from the film era and is not telecentric. Ergo, NO fast aperture, NO narrow DoF and NO benefit.

Well, I suppose your wallet would be lighter, even if your camera bag wasn't.

20
Lenses / Re: Lens dilemma for night sky
« on: November 20, 2013, 11:19:36 AM »
I did quite a few tests using my Zeiss ZE 25/2, 50/2 MP and 100/2 MP. These are all superb lenses but like all lenses, they exhibit a combination of vignetting, optical aberration and field curvature.

On an APS-C frame, they can all be used stopped down 1 stop. On a full frame, they they are not good enough for astrophotography unless stopped down to f/5.6, f/4 and f/4 respectively. The same conclusion largely holds for the 21/2.8 except that the field of view becomes something of a liability rather than a help.

This should hardly be a surprise - even the very fastest astrograph from Takahashi operates at f/2.8 which is really about T/3.5 and can only illuminate an APS-C frame. 

You can draw your own conclusions on how this relates to the 16-35 and 17-40, neither of which is particularly sharp unless stopped down considerably. I have no experience of the 14 mm Samyang but I friend uses the 14 mm Canon lens quite successfully.

Secondly, I honestly don't know what the OP's problem is with a sky tracker. You can get a sharp foreground and sharp stars by layering two images. As others have pointed out, it is sensible to stack the astro-image so that you can suppress noise. It may have been linked to above but this ebook is worth study http://astropix.com/BGDA/BGDA.HTM .

If cost is the issue, a sky tracker is easy to make - basically two pieces of wood and a hinge and a screw to rotate at 1 rpm using your finger. Look up "barn door tracker." Here's a very basic one that's good for 30 minutes at least... http://psychohistorian.org/display_article.php?id=201303261529_barn-door

21
Hmmm... cheap at half the price.
Nope, scratch that idea. Not even cheap at a tenth the price...

It must be depressing running a rumors site when the only interesting material refers to other brands...

22
...Here is my message ... I NEED LESS NOISE ...

I'm not going to spend kilodollars on a camera that's just like the one I have.
...
The real issue is well earned customer apathy.

Spend half that on a 6D now, sell the other two, and rent a 1DX...and tell me it doesn't have lower noise than the 1D4.  It does...and has better autofocus.  As I said above, Canon will bring you a high megapixel studio camera with low noise, but be prepared to pay big for it.  If you'd rather use Nikon for the here and now, certainly a D800 is a cheaper and quicker alternative to waiting for a Canon studio camera.  They've sold the D800 new as low as $2600 recently, and may again...I personally will pass.

Rather than write another boring complaint, I guess I need to spell out why I'm delighted Canon's ILS sales are down.

It means the board will have words with the camera executives. Even if the market size is decreasing, the board will want to minimise the loss of earnings. Canon will try to grab a bigger slice of the pie, which means more interesting products and less drip feed. From my perspective, this cannot be bad.

Unfortunately, they seem determined to let others grab the pie first. This cannot be good.

23
[rant]
I am delighted with this news!

Here's why. I have something like $30k in EF mount lenses. Some are Canon, some are not but they are all premium offerings. I have a couple of cameras - a 1D4 and 5D2. I didn't really see much point in upgrading last time around because I don't need faster autofocus.

I'm trapped, I really resent Canon's unwillingness to compete where it matters to me. If I sold my lenses I'd be down around $10k... and anyway, Nikon does things backward.

Here is my message ... I NEED LESS NOISE ...

I'm not going to spend kilodollars on a camera that's just like the one I have. Nevertheless, in nine months or fewer, I will own a $3k, high resolution, low noise camera that carries my lenses. It's up to Canon to decide whether they build it.

Finally, I think that blaming the declining sales on economies is limp-wristed face-saving. Many of the world's economies are doing quite fine. The real issue is well earned customer apathy.

[/rant]

24
Lenses / Re: Ken Rockwell on Lens Sharpness
« on: September 24, 2013, 03:22:30 AM »
i try to avoid him... but noobs keep on quoting him.   ;)...
I've more than 40 years behind the eyepiece. I've done weddings, events, portraits, landscapes, pets, macro, street and even astrophotography at 4.30 am on a winter's morning. Some of my images have been published, some of my students have had their images published. Every now and again, KR presents a point of view that I hadn't heard....

...so by your reckoning, I suppose I must still be a noob. Thanks for putting me in my place.

btw... the quoted article is at least five years old. There were fewer photo sites then.

25
I bought a second cap for my TSE 17, dismantled it, applied a Dremel and added an 82mm wide angle adapter. With care, you can set it up so that filters have about a mm clearance from the front element. This arrangement works fine with some caveats.

1. As others have commented, the amount of shift is limited before the filter vignettes the image.
2. The Lee CPL filter can't be used because it is mounted outside the filter holder and casts a circular shadow onto the image. If you need a PL/CPL, the Fotodiox version is the only route I know of.

26
Technical Support / Re: Color Management Woes
« on: August 15, 2013, 08:56:56 AM »
I use a U3011 - if you put the display into Adobe RGB or SRGB modes and then try to apply correction, it seems to go a little strange. I find leaving mine uncalibrated in Adobe RGB is more than accurate enough.

On the odd occasion where accurate colour is critical, I find that ColorChecker with a session specific camera calibration is the only way to make the output reflect the input.

You might also consider whether the environment you're working in is changing your perception of colour balance on the screen. I think[\i] this happens but it's very difficult to test on your own.

Based on your comment to xROELOFx ... try switching the screen to SRGB for viewing the web images.

27
Lenses / Re: Lens flare.... I want it! :)
« on: August 03, 2013, 10:23:48 AM »
Get yourself one of these...
http://www.etsy.com/shop/DogSchidtOptiks

Yes, the company's name really is Dog Schidt Optiks. At least you know what to expect...  :)

28
IIRC, the 5D II produces the same noise at 1200, 1600 and 2000. I believe this is an effect caused by their being two programmable amplifiers in the signal chain. Whether it's real or imagined, astrophotographers try to exploit the knowledge to optimise performance.

I'm scratching here but I think the source was Roger Clark's site - http://www.clarkvision.com/articles/index.html

Personally, I'd invest in first rate noise reduction software (I'm using Noiseware at the moment.) For imaging in extremely low light levels, it's common to try to profile the noise pattern that the camera produces. When done with care, this is at least half a stop more effective than the noise reduction Canon offers.

More than noise floors, I'd be somewhat concerned about the 5D II's ability to autofocus in low light - the 6D may be a better choice here. I'd also be cautious about focus shift when using fast glass... make sure the MFA is optimised at the aperture you plan to use.

29
Software & Accessories / Re: Who Adopted Adobe CC?
« on: July 22, 2013, 06:56:37 PM »
Nope, I didn't choose the CC route and having been encouraged to try alternatives, it's very unlikely that I'll give Adobe any more money.
I found that Capture One Express does at least as well as a raw pre-processor and can send the image straight into Photoshop.

C1 Express cost me $35 a couple of weeks back... what's not to love? It does need quite a serious machine - so try before you buy.

30
EOS Bodies - For Stills / Re: Fantasy Dayhiking Kit
« on: July 21, 2013, 01:45:20 AM »
I can't think of much that would persuade me to take a 200-400 with me on a hike around the block, let alone go for a day walk!

Having done a lot of mountain trips, I learned that cameras in my rucksack were pointless - stopping to get them out meant a loss of rhythm and added to already long days. This meant my camera had to be immediately available. My pre-digital mountain gear usually had an OM-2 a 24/2.8, a polariser and a GND. Occasionally, a 50/1.8 would make it into my bag but it was seldom used.

Enter the 21st century and a period of "progress." Until a few months ago, I'd pack a 5D2, maybe a 17 TSE, 21/2.8 or 25/2 and maybe a 50/2 MP. If I was brave, there would be a 100/2 MP or a 70-200 II or 400/4 or something else. Add a couple of filters and batteries and it's lots of kilograms to lug and the walk stops being fun. If a longer lens went along, it was with a monopod which needs a lens bracket and I may as well take an L-bracket for the camera. All this adds up.

Having used a lot of lenses over more than 35 years photography, I realised that fast lenses come at a premium - backache. A moment's thought should convince you that switching from f/4 to f/2.8 has around 4-6 times the weight. (The lenses must have twice the area and be twice as thick. Frequently, there are more elements, the mechanics are more complex and the lens is twice as long.) Anyway, it got to the point that I wasn't taking my camera with me because it was just too much hassle.

All this made me give a try at a mirrorless camera for my walkabout toy. I take a 12mm Touit and a 18-55 and that's it... It's the first time in years that my camera weight approaches what it used to be. Most of all, it's accessible.

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