January 29, 2015, 09:31:06 AM

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Messages - epsiloneri

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1
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.

2
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.

3
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.

4
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.

5
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.

6
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!
 

7
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.

8
Post Processing / Re: Backup to Blu-ray
« on: January 04, 2015, 05:05:20 AM »
Wow, that is deep, I nodded off a third of the way down, dropped my blooming ipad.
:) I hope your ipad wasn't harmed in any way. An interesting thing about the internet is that no matter how fringe your query, there is bound to be a small group somewhere that makes it their life's mission to delve into that topic with excruciating detail. Archiving is such a topic.

I won't go into the endless details of RAID here but I will say that unless you are ready to face a steep learning curve and a lot of stress and expense, don't implement a RAID array for yourself any more complicated than a RAID 1 mirror.  It's just not worth it IMHO.  Not only do you need to understand the technology, you need to understand the hardware and how to operate it.  And once you venture past a simple RAID 1 mirror array, the hardware is critical for performance, acceptable reliability and even the possibility of recovery.
I agree with your points about RAID 5 being inadequate for the big disks of today, and that RAID 6 has slow performance. But RAID 10 is very expensive if you don't need the performance (for 5 or more disks, say) and RAID 6 should be good enough for on-line back-up solutions. Any non-enterprise user should stay with software RAID, so understanding hardware quirks shouldn't be necessary. I thus think that RAID 6 is more often the better option for the usage pattern expected for those readers of this thread with massive backup needs. Better still would be RAID Z2, using the ZFS filesystem that protects the data against corruption through bit rot, but that is more for technically inclined.

It seems like as drive capacity/density has increased over the last few years, so has the failure rate (or at least the likelihood of data loss).
I know there is the perception that this is true, but is it indeed factually true? Hard drive failures have always been an issue, with some notable examples, e.g. the IBM deskstar 75GXP (aka the "deathstar"), and more recently the Seagate 1.5TB Barracuda.

In the end, I think this about the drive quality is a bit of a red herring. Yes, you should avoid obvious duds (such as the drives mentioned above), and yes, enterprise disks have more stringent quality control. But in the long run, all drives, without exception, will fail. The trick is to plan for it, and take appropriate measures.

BUT - we are digressing.  This thread is about BACKUP.
While backup is indeed in the title of the thread, I think this thread is actually about data archiving:
The key difference between backup vs. archiving is that data backups are designed for the rapid recovery of operational data, while data archiving stores data that's no longer in day-to-day use but must still be retained.

I stated my thoughts above and I'll repeat that if you put your faith in writable dye based media, you better test it every year or two because there is a definite history of this type of media failing after a few years.
Yes, that is why regular non-LTH blu ray discs are a much better option. Or the (more expensive) m-disc DVDs. They are not based on organic dye, so do not decay on short time scales. LTH BDs use organic dye like regular writable CDs/DVDs, so don't use them for archiving.

9
Post Processing / Re: Backup to Blu-ray
« on: January 02, 2015, 05:30:26 PM »
There appears to be some confusion in this thread. Since long-term archiving of digital data is essential for me (and no doubt for many of you), I have investigated this in some detail:

Hard drives. Great for short-term storage, backups, but not for long-term archives. Biggest problem is not de-magnetisation of the disks (half-life is typically ~70 yr) but aging of lubricants etc, resulting in mechanical failure after 3-5 yr. The problem is actually exacerbated by storing the drives powered off, off-line. Best strategy is to store multiple copies and re-write the data every 2 yr or so. On-line discs are ok for backup, but too volatile for archive.

SSD/flash drives lose their charge over time and typically last 5-10 yr unless re-written.

Cloud storage requires high bandwidth connection, useful for smaller amounts of shorter-term backup, but not for archives. Do you trust the cloud storage provider to still keep your data safe 20 yr from now? Will the company still be around?

Optical media - considered to be the ultimate digital archival solution, adopted by libraries etc. Note that there is a huge difference between pressed media and write-able discs. Write-able CDs and DVDs tend to use organic dye that deteriorate in time - could be as bad as in a few years only. There are some exceptions, m-disc being a notable one which uses inorganic dye (in the form of "rock powder"!), but requires specially designed writers with extra powerful lasers. Regular blue ray discs also use inorganic dyes, so should be fine. There is also an m-disc BD version, but it is not clear if there is any longevity advantage yet (although they are marketed as 1000-yr solutions). Stay clear from the BD LTH discs, however, which are developed to use the same manufacturing processes as CDs/DVDs with organic dye, to significantly reduce the manufacturing costs. They have similar lifetimes as the regular write-able CDs/DVDs. Note that pressed media are different and should have lifetimes on the order of 100's of years. They are typically not useful for archival purposes, though, since you need a very big series before it becomes economically feasible to press discs.

Magnetic tape - the most economical archival solution for huge data sets is to use magnetic tapes, such as LTO. There are archival WORM tapes ("write once, read many") that are certified for 40 yr storage, and you can get a 2.5 TB tape for less than $60. These tapes are typically used by huge data centers. A problem is of course that the tape drives are typically > $1500. Perhaps they are rentable.

A good practice to protect from bit errors is to save redundancy information together with the data, in the form of error correcting codes (ECC). Popular software to generate these are ICE ECC, MultiPar, and dvdisaster (the last optimised for ECC on optical media).

Some general, disorganised rants about archiving that I nevertheless found useful.

In summary, hard drives are good for short term backups, (non-LTH) BDs for long-term storage of limited data generation rates (less than ~ TB/yr), magnetic tapes for large data rates (several TB/yr).

10
Technical Support / Re: Grand Canyon panoramas
« on: December 30, 2014, 01:17:46 PM »
Longer focal lengths are generally easier to stitch due to reduced projection effects.
Whilst that comment is just plain silly
Why do you think it's silly? Have you compared stitching photos from ultra-wide lenses to photos from long tele-photo lenses? Rectilinear lenses approximate the field of view by gnomonic projection on a flat surface, thereby converting a solid angle into a flat area. It is the same problem experienced when producing flat maps of the spheroidal Earth - the smaller the area covered, the smaller the distortions in the projection. That's why flat city maps look OK, while maps of the whole globe tend to look distorted.

Now, for a photo using a rectilinear lens, this distortion is a 1/cos(angle) function of the angle to the direction you are pointing the camera. With a long focal length, the difference between the centre and the edge will be much smaller than for a wide angle lens, so the image scale will be more uniform and the distortion smaller. That means that to stitch photos from wider-angle lenses, more geometric correction has to be applied in order to get adjacent images to match seamlessly. More required post-processing correction = more difficult to match well and loss of IQ.

11
Technical Support / Re: Grand Canyon panoramas
« on: December 29, 2014, 05:43:52 AM »
It doesn't matter what lens you use.
Longer focal lengths are generally easier to stitch due to reduced projection effects. Depending on the field of view intended to be captured, it might not be practical to have lenses of very long focal lengths as the number of required individual shots for the stitch may become too many. E.g., on full frame a 100mm lens needs 2*pi/(0.7*36/100) = 25 shots for full 360 degree panorama in landscape mode (with 30% overlap), 38 in portrait mode. If you also want more vertical coverage, the number of shots grow accordingly.

12
EOS Bodies / Re: High Megapixel Camera Coming in 2015 [CR3]
« on: December 17, 2014, 12:52:34 PM »
The 5DIII will be 3 years old in March next year. A move to 50MP will pretty much follow Moor´s law.
Camera resolution has historically increased way slower than Moore's law. Canon 10D had 6.3 MP in 2003. Following Moore's law, we should have GP-cameras by now. This is the reason I find complaints about too many MPs due to limited computer resources exaggerated. Relatively speaking, we have more than  50x more computer performance (memory, storage, GFLOPS...) per MP than we had in 2003.

13
Canon General / Re: Canon USA Addresses the Gray Market
« on: December 17, 2014, 02:57:36 AM »
And from another perspective, Canon USA products are popular gray market here in Europe. Obvious caveats are a shorter one-year US-only warranty, American-style power cords, and noticeable import duty. Documentation in our native languages is available online from Canon, so that's not a problem. For lenses, focus distance units are given in both feet and meters, so that's no problem either  :P

14
Canon General / Re: Canon USA Addresses the Gray Market
« on: December 17, 2014, 02:44:23 AM »
That power cord must be made of pure gold to be worth £1199
Perhaps in the same class as this one, for $1999.99?

15
Lenses / Re: I *HATE* UPS.
« on: November 29, 2014, 08:31:24 AM »

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