March 03, 2015, 10:03:37 AM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - epsiloneri

Pages: 1 2 3 [4] 5 6 ... 26
EOS Bodies / Re: Patent: Microadjustment Automated
« on: January 15, 2014, 05:40:02 AM »
Hm, this sounds very much like what I suggested in this forum, 3 years ago:

1) AF focus on a target, say a properly aligned focus target. The camera registers what it thinks is the best focus.
2) Without moving the camera or the focus tagert, go to 10x live view and manually focus to what you think is the best focus, push a button or something for the camera to register what your preferred focus is.
3) The camera makes use of info from 1 and 2 to compute MA.
Alternatively, one could let the camera itself compare the AF between the AF sensors and the live view contrast AF, and compute MA under the assumption that live view AF is more accurate. That would be even simpler, and according to my experience, live view contrast AF is nearly always accurate (but slower). Contrast AF is not affected by front/back focus issues, since it uses the actual detected image for AF, so it would be perfect to correct for AF sensor MA. I can imagine setting up the camera on a tripod and align it to a focus target, select "calibrate AF" from a camera menu, and then let the camera automatically cycle through 10 AF measurement cycles (say), computing the best MA. Why not, Canon?

I'm glad Canon listened :D I hope this makes it into firmware at some point...

Canon General / Re: History: The Original Canon EOS 5D Camera
« on: December 28, 2013, 04:44:06 PM »
I'm throwing a flag on this statement.
I'm not sure what this idiomatic expression means, but I suspect it's not a compliment on my insightful post...

First off, anybody willing to accept the overall IQ of the 5D over later versions should have no problem adjusting color in ACR or other top-end editors. Secondly, since your statement is non-specific, it has no vlaue in a 5D vs "anything else" conversation.
In the text you quote I was responding to a specific question by privatebydesign (here rephrased): Why is the colour reproduction of different sensors discussed at all, when profiling ought to make them all identical? As I explained, the mapping of a full spectral distribution into three numbers (R, G, B) depends on the particular filter curves of the sensor. Profiling helps in making this mapping as close as possible to some standard, but it is in general not possible for sensors with different filter curves to give the same colours for arbitrary spectral distributions, no matter how careful the profiling. I can give a more detailed explanation with examples to help you see why this is so, if you are interested, but I suspect you are not.

In summary, that is why claims of "better colour fidelity" of a particular sensor (in this case that of 5D) cannot be simply discounted by arguing that you can always profile away any differences, since that is not generally true.

Picture Styles does have some limitations, like getting those settings applied to RAW files in third party software, but it is very powerful, with six HSL primary colour adjustments, there isn't much you can't correct for, certainly the differences between a 5D and a 5D MkIII are no issue.
I'm sure the colour reproductions you can get from 5D and 5D3 are similar enough to not be an issue, but I find the claims of 5D's higher colour fidelity interesting and wouldn't mind seeing some evidence for it.

Canon General / Re: History: The Original Canon EOS 5D Camera
« on: December 07, 2013, 03:54:05 AM »
I still preferred the colors out of my 5Dc than my MK3s. I skipped the mk2 series because it wasn't worth upgrading for me.
I never understand comments like this. It is digital, why not profile your camera to get whatever "look" you want from it?
There's more to colours than simply three numbers. E.g., the colour separation (amount of "cross-talk" between colours) might be different between different detectors (I'm not saying it is for 5D and 5D2, just that it could be). The Bayer detector has three filters: R, G, & B. By making the filters broader in wavelength, you gain some sensitivity, but you also run the risk of having the filters overlap in wavelength and counting the same light twice, e.g. for both R and G, and that will decrease the colour fidelity in your image compared to filters where there is less overlap.

So, not all detectors necessarily reproduce colours the same way, and it is no possible to correct in software (because it would be an ill-posed inverse process).

Landscape / Re: Milky Way near the moon?
« on: September 15, 2013, 02:35:53 PM »
This is the reason pictures of the moon taken by the Apollo astronauts do not show the stars... contrary to the beliefs of some conspiracy theorists  ::)

Canon General / Re: Lens advice for New York City
« on: September 15, 2013, 02:06:25 PM »
Hehe, an ultra-wide lens.. how could you expect any other advice from a user nicked Canon 14-24? But from your options, yes, I agree.

Lenses / Re: Best setup for falling stars
« on: August 28, 2013, 01:22:59 AM »
I meant I wanted to shoot the whole sky with the comet in it, and feature part of the terrestrial view as well. 
I see, well, then perhaps a fish-eye would serve you good. But generally, if you choose a very short focal length, the comet will not look as impressive (unless it is very impressive). If you want terrestrial features in the foreground, another strategy is to choose a time when the comet is nearer the horizon, and use a focal length more appropriate for the comet.

Incidentally, how well would a 300mm lens work on the Vixen Polarie?
I have no personal experience with it. The Polarie is intended for more wide-angle work, but is rated for 7 Ibs. of load, so it could potentially take a 300/4 for some 30s, if properly polar aligned. A 300/2.8 would probably be too much, including mount head and camera. An Astro-Trac could be the better mobile option, or a dedicated "light" tracking mount like the iOptron ZEQ25GT if mobility was not essential (i.e. no hiking with equipment unless you have plenty of assistents).

At 300mm it would be difficult to get foreground (but could yield spectacular results if you did; compare with full moon pictures showing foreground). You would ideally have the foreground high above you (a mountain or hill) to avoid seeing the comet through too much atmosphere. For a foreground project, I think 35-100mm would be a better trade-off between seeing both the comet and the foreground well enough. But as you say, it depends a lot on the comet.

If you haven't already, I would recommend you to look at other's comet pictures from past great comets, to probe the possibilities and get inspiration. Just remember that the last really great comet, comet Hale-Bopp, was in the pre-digital era (1997), so options were more limited then.

Lenses / Re: Best setup for falling stars
« on: August 27, 2013, 05:36:29 AM »
Nice image and very good advice.  Recently I have looked over the lens offerings, and tests...decided to go two routes for the object of my own night time pursuit, the upcoming comet ISON.  Assuming it looks like it will be worth going to the trouble, I will buy a Sigma 35mm f/1.4, and do (perhaps 5-shot-overlapped) stitched panoramas of the comet.  There simply is no other wide or medium wide lens that compares to its resolution...even the Zeiss 21 or 25mm offerings...let alone any of the 24 f/1.4's.  I also have decided the very best, sharpest wide angle lens, is also the least expensive, the Samyang 14mm f/2.8.  So that one is kind of a no-brainer (obviously it would be best for single shots).  It might be interesting to try a motorized mount as well...but would not help for the terrestrial aspect of the shot.  Of course if the shot is stitched, it would work...but the mount might hamper the ability to pan while doing the shots in succession...don't know.

Thanks! I would love for comet ISON to require stitching when using a 35mm lens, but I wouldn't count on it. Predicting the tail size is near impossible, and it may very well be only a few degrees in size, e.g. more suitable for a 300mm lens (on full frame). See image of Pan-STARRS by surapon earlier in this thread, compared to the size of the moon. We will know when the time comes (December). The Sigma 35/1.4 could be nice to acquire for other reasons, of course. Most important advice is to seek out a dark location. It makes a HUGE difference, since comet tails (unlike stars and meteors) are extended of faint surface brightness.

Some motorized mounts can drive on half the celestial rate, effectively increasing your exposure time 2x without introducing motion blur (e.g., the Vixen Polarie) for stars/foreground.

Lenses / Re: Best setup for falling stars
« on: August 25, 2013, 04:38:49 PM »
Congratulations on your catches! Though in the images you posted only 20130813-0132 and 20130812-0129 look like meteors. All of your second set are definitely satellites. Meteors can be tricky to capture, but I have a good recipe and I'm sorry I wasn't able to share it with you before this year's Perseids. Well, there are other showers (e.g. the Leonids) , and perhaps you will have the opportunity for a repeat with good weather next year, or for the moonless 2015 Perseids.

A few relevant things about meteors:

  • There are more fainter meteors than brighter
  • They flash in a fraction of a second (longer for brighter ones)
  • Showers appear to originate from a point, called the radiant
  • Meteors (even for showers) are as likely to happen anywhere in the sky, and are unpredictable

1 & 2 implies that in order to catch as many meteors as possible, you should aim for maximum practical sensitivity while limiting the background as much as possible for the best contrast.
  • Maximum aperture for your lens
  • As high ISO as you find acceptable
  • The shorter the exposure (longer than the expected duration of the meteor), the better the contrast, i.e. the brighter the meteor looks like relative to the background/foreground. There is a trade-off to be made, of course. In practice, using the longest exposure that maintain dark skies does not significantly worsen the contrast, so go with that. This is where you realise you need dark skies, as city skies easily can saturate in less than a second, while you can go on for minutes before that happens in truly dark locations.
  • Keep shooting repeatedly for as long as you can.
  • With dropping temperatures, watch out for dew on the front lens. Lens hoods help a bit, but for wide-angle lenses they are not very constraining.
  • Watch your focus, use live view on a bright star. For a slow lens (as the EF-S 10-22), use some other, bright faraway light, or focus during daytime and lock it.

What about focal length? With a wider lens, you cover more sky, so are more likely to get a meteor in the field. On the other hand, its image will be smaller and less impressive than if you were lucky to catch it at a longer focal length. Again, it's a trade-off.

For your alternative, I think the lens choices you made are the best given your selection, but as you've already concluded, it would be better to reduce the exposure time of the 5D3, perhaps using 10s with ISO 1600 or 3200. That would improve your contrast by a factor of 3. For the 7D. it's hard to improve your strategy, since going beyond ISO 1600 gives pretty noisy results.

I also photographed the Perseids this year, but I did it in a very lazy way. I happened to visit my parents-in-law house on the countryside, where they have dark skies, so I just went out at midnight and set up the camera to shoot repeatedly (using a remote and locking the shutter button). Went to bed, and came back to empty the net after two hours. My settings:
5D3+24/1.4L @ 1.4, 15s, ISO 1600. Since I wanted to capture the perspective effect of the radiant, I included Perseus in the field (but no interesting foreground object... I save that for 2015!). In ~500 frames, I identified ~50 meteors, out of which I produced a mosaic from the brightest half (seen below). The mosaic took some time to produce in photoshop, since I had to match the rotating background of stars. Next time I'll perhaps use a mount with drive, to simplify the process.

I think 24/1.4 is pretty much ideal for meteors. Unfortunately the 24/1.4L has awful coma, so next time I will probably try the Samyang 24/1.4, which is supposed to show less (see this thread)

I also found hundreds of satellite tracks in my images. The easy way to identify them is:

  • hey are generally white (reflected sunlight). Meteors are colourful!
  • They last for more than a fraction of a second (typically minutes and can almost always be seen in consecutive frames)
  • Their streak don't generally show the same light distribution as meteors (though a few do).

Lenses / Re: EF 24/1.5L II and astrophotography
« on: August 10, 2013, 09:35:47 AM »
Thanks! Indeed, my lens copy doesn't seem worse than anyone else's with regard to coma, and the Samyang 24/1.4 appears to be the significantly better option for stellar landscapes.

Lenses / EF 24/1.5L II and astrophotography
« on: August 10, 2013, 04:12:48 AM »
I know from experience that the point-spread function of the EF 24/1.4L II wide open is very poor, and thus not ideal for astrophotography (the stars look funny, in particular in the corners of the frame). Since fast wide lenses are perfect for capturing meteors, I used it anyway last night and managed to get a beautiful Perseid. The stars, however, look pretty terrible. I always thought it was the lens that was constructed that way, for daytime photography and non-point sources it is fine, but now I start to wonder whether I perhaps have an  unusually poor copy. Does anyone have experience with the EF 24/1.4L II for astrophotography, and are your results (for the non-round shapes of stars) as bad?

The image below is approximately 1/4 of the 5D3 field, the lower left corner. The faint streak to the right is a satellite. The imaged has been scaled. ISO 1600, 15s, F1.4, non-guided.

Lenses / Re: Focal Reducer
« on: July 09, 2013, 08:33:38 AM »
Unfortunately, a focal reducer for fast lenses at maintained IQ will remain a dream. An EF to EF-S reducer would be wonderful: it would effectively make your APS-C camera equivalent to a FF camera.

EOS Bodies - For Stills / Re: I love big gear
« on: January 24, 2013, 03:29:17 AM »
Pansies  ;D The LSST camera will be the largest digital camera ever constructed, measuring roughly 5' x 10'
And that doesn't even include the front lens: the 8.4 meter diameter mirror and the building to support it!

Lenses / Re: Which (if any) non-L lenses are enviro-sealed?
« on: December 14, 2012, 02:38:26 AM »
My main lens though is the 100-400L, which is less sealed than the 70-300L. After some hours in the rain, the 100-400L will develop condensation inside which blocks the optical path. Unless you really love the soft focus look, I switch to a backup lens and keep shooting.
Switching lenses during rain to get better sealing doesn't sound like a good idea, unless you can get away from the rain to do that.

Lenses / Re: Canon EF 50 f/1.4 IS in 2013 [CR2]
« on: December 12, 2012, 03:11:33 PM »
I'm a bit skeptical despite of the CR2 rating. The fastest Canon with IS is the EF 200/2.0L IS. I don't know if any other manufacturer has a faster lens with IS, but I suspect not. It would be a major leap to get IS to a f/1.4 lens.

I'm more inclined to believe an EF 50/1.4 II.

Lenses / Re: 1Dx or lenses
« on: November 23, 2012, 12:43:50 PM »
With both the 100/2.8L and the 70-200/2.8L IS II, a 135/2.0L would a bit redundant (unless you shoot concerts). I agree that a standard zoom seems to be missing in your lineup. The 24-105/4L or one of the 24-70's should do.

Pages: 1 2 3 [4] 5 6 ... 26