February 27, 2015, 04:43:09 PM

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Messages - epsiloneri

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1
Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 12, 2015, 12:46:19 AM »
I believe though that the photos from Samyang apart from the exceptionally low coma exhibit yet another property of Samyang: Decentering  :(
Yes, you're right - I will have to make some more experiments to see how bad it is :(

the sample you posted looks about right.
Ok, so the Sigma 35/1.4 Art has the best coma you've so far seen a 35mm exhibit, although I would say it is still quite poor. I guess I'm just disappointed in that the 35 & 50 Art lenses seem so perfect in all other respects (including AF, for me) that I wouldn't have thought their coma to be this bad. I thought it perhaps was an inherent problem with fast designs, but then the Samyang proved this wasn't so (though it has other problems, it seems). So perhaps the SIgma 24/1.4 Art will indeed have improved coma, I sincerely hope so, because the EF 24/1.4L II is as bad (or worse) as the Art examples posted above [wide open].

2
Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 11, 2015, 05:03:45 PM »
As I mentioned above, I accept very bright "square stars" in the far corners of full frame.
I would too, that's not what I mean by poor coma.

As far as I'm concerned coma is the one area where it most obviously beats the Canon 35 IS (aside from max. aperture, of course). 
I start to wonder if I have a defect copy...

Anyway, I could not find a good 35mm Art starscape example in my archive and unfortunately the sky is overcast. Fortunately, I found a neighbour with some christmas light decorations left on the balcony rail, so I could use them as point sources. Instead of taking one picture, I focused in the center and then took one picture with the balcony in each corner of the field of view (in manual mode exposure and focus).

To show that coma doesn't necessarily need to be this bad, I also performed this test with a Samyang 24/1.4, also wide open. I also found a starscape with the Sigma 50/1.4 Art, attached. From these tests, I stand by my statements that the coma of the Sigmas wide open is poor, but the Samyang 24/1.4 together with the Sigma press release indicating they may have made some progress in this area, gives me some hope for the Sigma 24/1.4 Art.



3
Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 11, 2015, 10:52:45 AM »
The Sigma 35mm f/1.4 Art has very little coma wide open.
Is your experience perhaps from using it on APS-C? From what I recall on FF, the coma was not subtle. I will search for samples or obtain new ones tonight, weather permitting.

4
Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 10, 2015, 03:35:09 PM »
Which fast 35mm lenses have less coma than the Sigma Art?  I haven't tried all that many, but even though it wasn't perfect the copy I briefly owned was far better in terms of coma than, say, the Canon 35mm IS.
I don't really know, haven't tried any other. Perhaps it's the best, even though it's no good [wide open]. For a long while I thought it perhaps impossible to make a fast 24mm with little coma, but then the Samyang 24/1.4 came along and proved me wrong. Maybe the coma-optimised 35mm design just hasn't happened yet.

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Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 10, 2015, 02:55:32 PM »
Off topic, but I would say the ultimate landscape astrophotography lens would be the Samyang 14mm/2.8. But I guess not as fast.
Depends on your needs... for meteors and aurorae, speed is important. Meteors also tend to look less impressive at 14mm, and composition becomes more challenging. I certainly would prefer a good 24/1.4 :P

what I meant was that when shot wide open, the 24L II is very sharp, the 35L is modestly sharp, and the 50L is a bit soft.
I don't find the EF 24/1.4L II that sharp. Only when stepped down to 2.8 does it become reasonably sharp, and then only as sharp as the EF 24-70/2.8L II zoom (worse center, better in the corners). And as mentioned before, the coma is absolutely terrible. So I find there is definitely room for improvement.

6
Lenses / Re: Sigma 24mm f/1.4 Art announced..
« on: February 10, 2015, 10:03:21 AM »
Landscape Astrophotography! Hope it is low-coma at f/1.4 (at most "square stars" in corner). I have to say that it is a challenge getting dark enough skies to profit maximally from f/1.4 on the 35mm Art.
Indeed, though the 50 and 35mm Art unfortunately have quite poor coma wide open. The press release gives some hope, but I will also wait for a reputable review. A low-coma 24/1.4 would be a dream. The Samyang 24/1.4 seems to be the best so far in that respect (though don't know about the crazy expensive Zeiss).

7
Lenses / Re: New Unique Macro Coming? [CR1]
« on: February 09, 2015, 06:34:41 PM »
I have a Mirex Pentax 645 to EOS TS adapter and I have experimented with the Pentax 120mm Macro with it.
Cool, thanks for your story.

8
Lenses / Re: New Unique Macro Coming? [CR1]
« on: February 09, 2015, 04:14:02 AM »
Are you asking for the MP-E65 to be in focus as you move the lens in closer or further away?
That would be really nice, and wouldn't have to break the laws of physics. Just fix the plane of focus to, say, 300mm from the camera image plane. Then let the magnification change by extending the lens by the appropriate amount, without changing focus distance from the image plane. The subject-to-front lens distance would change, but not the subject-to-camera body distance. One would still need a rail for focus stacking, but it would cut down on one variable for framing.

My 15mm f2.8 fisheye with MFD of 15cm can focus as close as a macro.
Yes, but can you get 1:1 magnification? :)

Softfocus like the 135/f2.8? No, it wouldn't be a 'world first' - I had that feature with my non-L 100mm macro. The lens was also capable of activating the soft focus feature at random.
Must have been a problem with your specific copy, I see no significant IQ difference between the L and non-L 100mm macros (I've used both).

9
Photography Technique / Re: How to Expose and get sharp Focus of Moon
« on: January 08, 2015, 07:43:37 AM »
There are now several posts that you get sharper images on the old 100-400 and now the new 100-400 II with IS turned off. Is that true for just these lenses or for all lenses? Why does IS cause problems? Does using a tripod cause the problems (I thought the newer lenses detected they were on a tripod)?
I don't think IS causes problems in this situation, since the exposures are so short. On the contrary, I think IS could even be helpful, to reduce residual vibrations from shutter/mirror. Probably not much with a good tripod, but at least not hurtful. For longer exposures (>1 sec), the matters are different, since the IS image tends to drift around on those timescales. In astrophotography, these longer exposuse times are commonly used, which is why I think many associate astrophotography with no IS, but as I said, it does not strictly valid for shorter exposures.

10
Photography Technique / Re: How to Expose and get sharp Focus of Moon
« on: January 08, 2015, 07:19:45 AM »
Congratulations, it looks like a real improvement!

There was some blurring during focus from the atmosphere, so clearer air may have helped improve this result.
If you are aiming for as much detail as possible of the moon (without foreground objects), it is generally best to shoot when the moon is as high as possible in the sky, since that reduces the air column towards it, and hence "seeing" (blurring) effects from the atmosphere. Also, avoid setting your equipment up close to a heat source (like an open window, line of sight closely over roof/chimney or warm car) as the heat generates blurring air turbulence.

Quote
Using 7D +100-400 II at 400mm and manual exposure my settings were 1/100 sec, f/8, ISO 100.  Used liveview at 10x and manual focus with cable release and 2-sec timer.
If you haven't already, you can gain some experience by varying your settings, taking a series of images for each setting. For instance, try using the lens wide open and go down in exposure time, try with IS on/off, and so on. The degree of image blurring due to atmosphere can be episodic, so try during different times of the night.

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Photography Technique / Re: How to Expose and get sharp Focus of Moon
« on: January 07, 2015, 03:57:44 PM »
I'll leave a proper response to jrista and the other astro-experts here, but did you turn IS off?  That will ruin a shot.
No, IS will ruin shots with long exposures (more than one second), but not for short exposures like this.

Since moonlight is reflected sunlight, a typical daytime exposure ought to work fine.  I shot in manual mode using 1/100 sec at f/11 and ISO 200.
Good argument regarding daylight settings! Though you should get better results by opening up the aperture and using shorter exposures and base ISO. Focal depth is really not an issue, vibrations much more so (though perhaps not in your case, using IS). F/11 actually gives less sharp images than f/8, due to refraction. I don't know what the optimal opening for the 7D is, but I'm guessing somewhere between f/5.6 and f/8.

I find focusing on the moon using live view comparatively easy. Just try to find as close an optimum focus as you can, and don't forget to switch off AF.

A good thing to know is that the moon shows less detail the closer to full moon you are. Half moon is optimal, and that is because the shadows cast by structures on the moon at the terminator are at their longest and most easily visible. Look at KeithBreazeal's great moon shots above, they also shows most of their detail close to the terminator (the border between day and night). I see Famateur made the same observation.

12
Landscape / Re: Geminid Meteor Shower Composites
« on: January 06, 2015, 04:23:44 PM »
Many thanks for your detailed answers!

Quote
4) Have you captured the same meteor in different cameras? I'm sure you have, I just couldn't see it easily by looking quickly.
Yes, there are quite a few "repeat" meteors.  The second and third composites are mostly repeats.  The only difference is the time at which the background image was taken.  The radiant was much higher in the third composite.

Another idea just occurred to me. I think it would be insanely cool to have a stereoscopic image of the meteors from a shower including the radiant. The cameras would have to be close to identical in setup and positioned about 10 km or more apart for good stereo effect. One day I am going to attempt it, perhaps enlisting a collaborator.

13
Landscape / Re: Geminid Meteor Shower Composites
« on: January 06, 2015, 04:44:54 AM »
That is excellent work, Wade! Thanks for sharing them, and particular the details about their creation. It is really helpful for others (like me) interested in meteor photography. A few questions/comments:

1) From your number of 5000 images x 25s / 4 cameras / 2 nights I assume you let the cameras stay exposing for about 9-10h per night. Since you did not use tracking mounts on the last 3, how did you avoid motion blur on the stars due to Earth's rotation? Also, it looks like the meteor streaks converge from a single point, despite the meteors being distributed over the night. Did you "move" the meteors to the appropriate positions in post? Did you have to take into account the variable distortion over the field of view? No matter how you did it, it looks good anyway.

2) I see no non-gemenid meteors, did you exclude them? You also removed satellites, airplanes, I assume?

3) Why did you stop down the TS-E 17/4Ls? Interesting that you have TWO of them! Or perhaps you actually used the Zeiss 15/2.8 on the second 5D3 (why else would you rent the Zeiss)?

4) Have you captured the same meteor in different cameras? I'm sure you have, I just couldn't see it easily by looking quickly.

5) It is interesting to me that the Gemenids show so much less colour than do the Perseids. Perhaps it has to do with the composition of the grains, or it is related to the relative velocity between Earth and the meteoroid orbits. I have not researched, just speculation...

6) I think your captures of the meteors are already perfected, so a next step for you would probably be to find some interesting foreground object to improve the composition and impact of the images, as in this example by extremeinstability on this forum. Another challenge would be to attempt capturing meteors at longer focal lengths.

14
Lenses / Re: Lens 'resolving power' vs sensors.
« on: January 05, 2015, 03:50:30 PM »
Photography isn't so much about the kit as it is about a great photograph. Too much attention on the science of photography can pull us away from the the reason we have the kit. Yes the kit helps, the science part...but really it's about the art of the photo not the process or kit. Talk to most great photographers and they rarely talk about kit or technique.
There is a wide range of great photographers, some pushing the techniques more than others, like e.g. Ansel Adams or Lennart Nilsson. Then there is photography where technique is of dominant importance, like in medical photography or the astrophotography that jrista engages in. Contrast this to e.g. photo journalism, where "f/8 and be there" is the guiding principle. What I want to say is, photographers put emphasis on different things, and there is no "right" or "wrong" amount of attention given to technical details. In general, though, I believe that mastering your tools by knowing their limits is helpful, even in situations where it's not critical. Knowledge is power!
 

15
Post Processing / Re: Backup to Blu-ray
« on: January 04, 2015, 06:55:55 PM »
LTO Tape (or DLT, or QIC, or 8mm, or 4mm or 8 Track, or Cassette or whatever) is a bit antiquated these days.
On the contrary, LTO is cutting edge in enterprise digital storage, and its usage is increasing. The latest revision from 2012, LTO-6, holds 2.5 TB uncompressed and can be read/written at a bit rate of 160 MB/s - that's faster than single hard drives, and enough to saturate a gigabit network. Future revisions are planned to store increasingly high data densities, up to 48 TB with 1.1 GB/s for LTO-10 (granted some years into the future). Archival reliability for LTO cartridges is far better than hard drives, they are designed for long shelf life. You can easily convince yourself by googling around. Wikipedia gives some good background info on LTO.

A worry for archiving is naturally that there should be drives able to read the media in the future. Given the general (and increasing) usage of LTO and the backward compatibility of newer revisions, I think it is safe to assume that it will be possible to read tapes 30 yr from now without going to expensive extremes. The same goes for optical discs.

I'd appreciate reading more from those respondents who have experience with LTO-n tape drives and media. 
I don't have my own tape drive, but at work we use LTO tapes for backups. The only advice I can give is to verify your data once written to tape, and perhaps write two copies to be stored at independent locations. I'd also recommend using WORM tapes for archiving, to avoid mistakenly over-writing data later. Make sure the drive you purchase is compatible with your system. LTO-3 stores 400 GB, and its data rate at 80 MB/s is still much better than you get for BDs. Plus, less swapping of media.

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