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Messages - noisejammer

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31
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

32
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...

33
...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.

34
[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]

35
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.

36
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.

37
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.

38
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...  :)

39
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.

40
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.

41
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.

42
I use my 5D2 for landscape work and have a good selection of Zeiss glass. Autofocus is thus totally irrelevant in my manually focused, live view, 0.1-shot-per-minute world. Since the 5D3 didn't offer much in the way of meaningful improvement - particularly resolution, dynamic range and low ISO noise, I decided to sit on my hands.

The cameras I have are still way better than I am and I don't want another camera that does the same job. If Canon releases something with a combination of enhancements that are significant to me, I'll take it. If not, my 5D2 / 1D4 / Fuji X-E1 combination is more than sufficient.

If - given the rapid development of the mirrorless segment this is a very big "IF" - there's a successor to the 5D4 (for lack of a better name), it will doubtless be quite a different animal from the 5D2. It might even be interesting.

43
EOS Bodies - For Stills / Re: 5D Mark II composition movement
« on: July 21, 2013, 12:37:23 AM »
I came across a 1D Mk IV which had a similar problem. I eventually tracked it down to damage in the dioptre compensation mechanism. I suspect the camera was dropped which broke the supports leaving a lens group free to wander around. As the camera was tilted, the optic would change its attitude wrt the prism and you'd be looking at a different part of the screen.

Anyway, the repair was quite easy - replacing the assembly took less than half an hour.

44
Lenses / Re: 50mm Primes that don't suck wide open?
« on: July 12, 2013, 07:43:44 PM »
Since the sensor doesn't actually detect light from a fast cone, it can't contribute to the bokeh

I'm not sure where you read this, but it's demonstrably false. I'm looking at two 7D + Sigma 50mm shots on my screen right now, f/1.4 and f/2, same subject/distance/etc., and the difference in bokeh is quite clear.
Apologies for trimming your post.

First, I'm well aware of the LL open letter and have referred people to it previously - here, on POTN and elsewhere.

I observed four effects -
1. Few people bothered to go to read the reference and digest its content.

2. It refers to a DXO study and there's a rabid hatred of DXO measurements, particularly since they tend to be quite scathing over Canon offerings.

3. Few people who read the letter did any testing  but this did not prevent them from commenting that it was a lie - perhaps a result of point 2.

4. There was a lot of nastiness - particularly from owners of 50L and 85L lenses - perhaps because they had a lot of dollars sunk in the lenses.

Because of this, I've changed my approach. I invite people to perform the experiments and simply judge for themselves. It cuts through the internet noise quite effectively.

Bokeh
Ok, so let's assume you've now performed the experiment using a 7D.

If you did it properly, you will have noted that the image is dimmer when the camera could not communicate with the lens. I venture that the same number of photons hit each pixel (within photon noise and your ability to align the tests) so presumably something else gets changed when the camera communicates with the sensor.

There is simply no way that a photon that is not detected can plausibly contribute to the bokeh. (If you doubt this, please suggest a mechanism.) Therefore, if there's a difference between in the image quality between (say f/1.4 and f/2), it can't be light that's doing it.

I strongly suspect that there is some image processing going on inside the camera to deliberately soften the image from lenses that have large apertures. It may be possible to demonstrate this idea by installing an aperture mask on a wide open lens and seeing whether the image quality changes (say between f/1.4 and f/1.8.)

Finally - another reference that may be of interest http://goo.gl/5We9r . Note how the 7D loses 0.65 EV when the sensor is illuminated by a f/1.4 lens. This strongly suggests that the pixels do not respond to light that's coming from a cone which is faster than f/2. Similarly, a 5D2 and 1D4 will lose 0.44 EV at f/1.4.

regards etc.

45
@Fleetie - thanks for doing the test.... I'll take a bow :)

@Drizzt321 - wide open an f/1.2 lens collects (1.4/1.2)^2 = 1.39 times as much light as a f/1.4 lens. This corresponds to 0.47 stops (not 1 stop.)

Of course, you would expect the f/1.2 lens to be brighter than a f/1.4 lens but this is NOT what Fleetie observed. When the camera communicates with the lens, it boosts its internal ISO (without telling you) so that the f/1.4 image becomes brighter than the f/1.2.

(IMO) This is a swindle that's perpetrated to persuade people to continue buying fast glass.

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