July 30, 2014, 03:51:24 AM

Author Topic: More Sensor Technology Talk [CR1]  (Read 11175 times)

scyrene

  • EOS M2
  • ****
  • Posts: 170
    • View Profile
    • My Flickr feed
Re: More Sensor Technology Talk [CR1]
« Reply #60 on: May 03, 2014, 07:06:48 PM »
The more you post, jrista, the more I respect you.
5D mark III, 50D, 300D, EOS-M; Samyang 14mm f/2.8, 24-105L, MP-E, 85L II, 100L macro, 500L IS II, EF-M 18-55; 1.4xIII, 2x III + 2xII extenders; 600EX-RT; EF-M--EF adaptor.
Former lenses include: 70-200L f/4 non-IS, 200L 2.8, 400L 5.6

canon rumors FORUM

Re: More Sensor Technology Talk [CR1]
« Reply #60 on: May 03, 2014, 07:06:48 PM »

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #61 on: May 03, 2014, 08:17:50 PM »
Lol, well I know you like the higher spatial resolution...but that only works if the lens is up to the task (at least for "spatial" resolution of the image itself...not for comparing final or effective resolution of the larger sensor to a smaller denser one at the same lens focal length, etc...obviously ultimate image quality is less of a factor in that case).  Not many lenses are up to the task.  Also I'm not saying the 600 ii is not able to pull it off, obviously of course it is.  For astro imaging, would you not still need to do a similar multi shot NR process, even for a 6D, 5D3, or 1DX sensor?  How about for the 24MP or 36MP Exmors?  Wouldn't the A7r be an interesting option (since it can be adapted for EF lenses)?  Or is the closer flange distance enough to discourage trying that, due to the higher ghosting?  I assume in that process, you are not using (and would not want to try to use) ISO settings above 1000 or so (meaning the Exmors would have clear advantage). 

If you are talking about astrophotography (honestly not really sure what your trying to get at here), then the answer would really be "none of the above". I use my 7D for AP only because it's what I have right now. As far as the best sensors for AP, one doesn't use a camera built for normal photography. Every normal photography camera "cooks" the images. Even Canon's, even though they cook them less than the competitors, are always modifying the raw signal in some ways, but more than enough that it can make it difficult to properly calibrate and integrate a stack of images to produce a low noise, easily stretched astro image.

Astro CCD imagers tend to be vastly superior to any CMOS image sensor from normal photography cameras. They are usually monochrome, therefor their spatial resolution, particularly for color filtered frames, is higher despite the fact that they often have slightly larger pixels.  They use higher grade silicon and fabrication processes, and usually have higher Q.E. (55-65% is common for low end CCDs, 70-96% is what you get for higher end CCDs). They also usually have considerably higher dynamic range. About the best DR for a modern CMOS imaging sensor for a normal photography camera is around 40-43 dB. Even a lower end astro CCD gets about 55dB, and the midrange and higher end CCD can get anywhere from 70-105dB of dynamic range. About every 3dB is a one-stop improvement. Most of the nice high end astro CCDs that use the Kodak KAF-16803 full frame (36x24mm) sensor with 9µm pixels (or similar variants, some use a 36.7x36.7 4096x4096 pixel square Kodak KAF sensor, but it's specs are generally the same) get between 79 and 91 dB of dynamic range (depends on the actual grade). FWC is around 100,000e-, read noise is about 9-11e-, and dark current (when fully cooled) is around 0.02e-/s or less. Factoring in read noise, that's anywhere from 24-29 stops of dynamic range...which utterly TROUNCES the D800 and any other Sony Exmor based imager on the market.

When it comes to core technology, a lot of the technology that matters for normal photography really doesn't matter a wit for astrophotography. Spatial resolution is an important factor for normal photography. Not the single most important (you should know me well enough by now that I don't believe in the concept of a single most important feature for IQ :P). When it comes to astrophotography, it's a very keen balancing act, between getting enough resolution, but not so much that your dramatically oversampling your subject. You have a number of factors that go into producing a "spot size", the size of a diffraction-limited star at the sensor. When you factor in seeing (atmospheric turbulence), most of the time it's difficult for amateur astrophotographers to find seeing good enough that stars are less than 2-3" (arcseconds) in diameter. For nebula, galaxies, clusters, basically anything non-planetary, you want your sensor resolution to be fairly close to your spot size, not oversampling them too much, but also not undersampling them. For the most part, a pixel size around 5-6µm is pretty ideal for this purpose, but most astro CCDs allow pixel binning, so you can make your effective pixels larger or smaller as necessary when adding barlows or focal reducers in order to match your pixel size to your seeing/spot size. Astrophotography is also dependent on having sensitivity to wavelengths of light that are either utterly unimportant for normal photography, or which may even have a negative impact on color accuracy (i.e. deep reds and near IR and near UV), while concurrently being averse to other wavelengths that are often very important to normal photography (i.e. the various bandwidths within which sodium and mercury vapor lighting emit...yellows, greens, and violets, which contributes to light pollution in cities, is often filtered out with light pollution reduction filters.)

What I need for astrophotography is very different than what I need for stills photography. There is nothing wrong with more spatial resolution for normal photography, more of it certainly doesn't hurt. Total sensor area is also important for normal photography for VERY different reasons that it is important for astrophotography. Total sensor area leads to higher real sensitivity with normal photography. Larger sensor will always trump smaller sensor when it comes to high ISO performance.

With astrophotography, most of what your imaging are point light sources. This makes full well capacity, quantum efficiency, and having a low gain setting far more important than high ISO performance, as the higher you crank gain (or ISO), the faster your stars saturate and "bloom" (clip, then begin to spill over into neighboring pixels, which also eventually clip). Physical aperture size vastly more important than relative aperture in astrophotography, as it doesn't matter so much how fast you image as how much light you get from each and every definable point of the sky that you are resolving.  Physical aperture is also the primary factor in determining limiting magnitude, so a larger physical aperture, even if the telescope is effectively only f/8 or f/10, is important if your goal is to resolve very small details of very distant objects, or very small, dim stars.

It's generally illogical to compare normal photography needs with astrophotography needs. They are very different. What I argue for here on CR is very different than what I may argue for in the astrophotography threads here, or on astrophotography forums. Conflating what I've said about CMOS image sensors for normal photography with what I may have said about astrophotography is generally pointless, as there is no real correlation between those two types of photography.

Have you seen Sigma's internal balance sheets and accounting?  You claim you know where their money goes.  I admit obviously their foveon sensor is still very much in infancy, which is a shame.  However, they did buy the rights to the design from the American company.  And, they are the only ones producing a sensor like it (so far).  They even have a new one (which you were quick to trash, without ever having tried it). 

Your kind of missing the point of what I was saying. It doesn't matter how much money is involved. My point is that if they dumped their Foveon advertising budget into Foveon R&D, the money would be better spent. Regardless of how much they actually spend. A truly competitive Foveon (one that has BOTH the color fidelity advantage as well as competitive spatial resolution) would speak for itself, in images and by a much larger community and word of mouth.

I see nothing wrong with giving Sigma credit for trying, for being different...it seems like it works for the segment of the market they have laid claim to. 

I've never faulted Foveon for trying. Ever. I've only faulted them for lying or being misleading and creating this mistaken notion that somehow, Foveon's layered pixels somehow give them the magical ability of creating more resolution out of nothing. Sigma has a misleading, fallacious advertising agenda for Foveon. They seem to think they NEED to falsely trump up Foveon's resolution capabilities in comparison to bayer sensors, when they really don't. That's my beef with them. If they were truthful and sold Foveon on it's REAL strengths, I'd have nothing to call Sigma out for, and we wouldn't be having this discussion.

Primarily they make lenses, after all.  The cameras are a very small niche.  Why would you expect them to be able to spend the funds necessary for the R&D to develop the sensor to your liking, when Canon and Sony have (as yet) not been able to do it?  Canon is trying to do it, and they are the largest camera company in the world.  Yet it's still not even for sale.

Based on the earliest patents from Canon for similar technology, they haven't been at it for even half as long as Sigma (or the prior owner of the technology). Hence my quip about Sigma better spending their money on R&D...it shouldn't take so long for such an intriguing sensor technology to go...almost nowhere. It was at 4-5mp for years, then it had a jump in the last couple of years to higher resolution, but it still lags behind bayer sensors. Foveon still suffers from noise problems, so it's never been as viable at high ISO (which immediately makes it a non-viable option for a LOT of photographers). Some of the technology in Canon's patents already surpasses Sigma's technology that is already in Foveon.

I sincerely hope that as more cash flows into Sigma from their lens division, they will be able to better prioritize more funds for Foveon R&D. I do like the core concept. I just don't believe that Sigma has done Foveon justice (so far). Things could change, and if/when they do, I'll applaud Sigma for the change...but to date, the snail is still losing the race.

(And let's face it, if Sigma spent $1 billion to develop it, it would still be a failure in your opinion, no matter how good it ultimately was...how is that fair or unbiased?)

Now your just assuming things. If you actually learned anything about me over my time on these forums, you would understand how ludicrous that assumption is. :P

I could care less, really, about how much money Sigma spends. What matters more to me is whether they money they spend results in progress that produces real value, and whether they HONESTLY sell the thing or whether they resort to misleading factoids and spurious claims. If Sigma could make the Foveon a truly competitive sensor TECHNOLOGICALLY (and it certainly has the potential, nothing wrong with the technology itself), it wouldn't matter if it cost $1,000,000 or $1,000,000,000...so long as in the end they turned enough of a profit to continue investing in the technology and keep it competitive. If they end up failing in the end, well it still wouldn't matter if they spent a hundred grand or a hundred billion, it would all be a waste in the end.

It will be both interesting and amusing, to see your criticism of Canon's new camera (assuming it even uses this technique...for all we know the next full frame model may not even use it after all.  It's just rumors...)

Again, your disgust with Sigma for simply existing, is juvenile, misplaced, and unnecessary.  As is your harsh view of those who use, or have used their products.  If we state our opinion of the images we got from using the camera, who are you to say we don't have a right to state it?

And were back to the personal insults. You and I do indeed have a mutual loathing of each other, and I have no interest in being friends with you...but I'm really trying to keep it off the public forum. No one else wants to see us fight, so I respectfully ask that if you want to insult me, please use PMs. Then you can get as nasty and hateful as you want.
« Last Edit: May 03, 2014, 08:19:55 PM by jrista »
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

dilbert

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 2688
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #62 on: May 04, 2014, 12:05:57 AM »
...
This doesn't prove anything. For one, the reviewer is highly biased.

If you want to stick your head in the sand, then don't let me stop you.

The reviewer raves about the camera; but in the "what's wrong" section states:
    poor image quality above ISO 400

Seriously? A camera released in 2012 that has poor image quality above ISO 400 - if that's not a biased review I don't know what is.

Ok, so are you saying that because the camera doesn't take good photos above ISO 400, it must therefore suck and everything else about it is of no consequence? Or are you saying something else?

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #63 on: May 04, 2014, 12:30:20 AM »
...
Sigma wastes far too much time, money, and effort trying to trick potential customers into thinking they will get more resolution with a Foveon than a bayer, which is just a blatant, outright lie. I don't appreciate that, and yes, I fault Sigma for it. If Sigma would take a big chunk of their false advertising budget and inject it into their R&D department instead, I think they could make Foveon viable both on the color fidelity and spatial resolution fronts, and actually have a real competitor on their hands. But sadly, they keep pushing their missleading advertising.

If Canon come out and say that their 15MP layered sensor is in fact 45MP, how are you going to
respond? 15 is just an example, maybe it will be 20, maybe some other number. But the challenge will be how to market it as being superior to a 36MP Nikon or a 36MP Sony.

If Canon comes out and makes spurrious claims about how their 15mp layered sensor is really a 45mp sensor, I'll be the first to call them out for using the same missleading tactics as Sigma. I almost hope they do, and if they do, I really hope your still around, because I would love to prove to you that I stick to the facts and the physics, regardless of brand.

How many times have you heard me say the D800 has a superior sensor at low ISO, or in terms of resolution (hell, just a couple posts ago I stated that the D800 had twice the resolution as the 1D X)? I only dispute what's wrong. The Foveon, like Canon's DPAF, is not a magic bullet. It cannot give you more resolution than it actually has. Canon DPAF cannot give you more resolution, because DPAF isn't about resolution. The D800 cannot give you better high ISO performance because high ISO performance is physics-limited. I could care less about the brand...all I really care about are the facts, the engineering, and the physics when it comes to what a sensor or camera is capable of.

I would have thought my tiraid against the mistaken notions of Canon's DPAF also being a magic bullet for better IQ in the future would be an indication of how little I care about brand when debating the facts.

Quote
I spent over ten grand on a lens last year.

Why should we care about this?

Well, if your going to intentionally miss the point, you shouldn't.  :P
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

dilbert

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 2688
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #64 on: May 04, 2014, 12:43:24 AM »
And were back to the personal insults. You and I do indeed have a mutual loathing of each other, and I have no interest in being friends with you...but I'm really trying to keep it off the public forum. No one else wants to see us fight, so I respectfully ask that if you want to insult me, please use PMs. Then you can get as nasty and hateful as you want.

I have a feeling a lot of people prefer hurling insults when they have an audience ;)

It would seem that the list of those that enjoy hurling such insults grew by one during this thread :)

3kramd5

  • Canon 70D
  • ****
  • Posts: 315
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #65 on: May 04, 2014, 10:53:57 AM »
Actually I did read it, but I'm not wasting my time reading this new one.  Try to help some people out, and they bite your head off.  Irrational?  Indeed...and you're extremely guilty of outright insulting me and trolling me, many times over.  Again...I asked a simple question, how about a simple answer that is less than 100 words, with no insults and no whining?  What is the reason you would not buy an A7r, to try for astrophotography?  Is it the ghosting?  I could understand that, if that's what it is.  It can't be the cost, because we both know how upset you got when I suggested you would not "buy a $30k lens right this moment"...and you said you would, if you thought it would help your photography achieve new heights of greatness.  You could also use the A7r for static bird photography, something a $1995 CCD imager couldn't do.

Glancing at his gear wish list, it looks like he's more into action than astro. An A7R is 2500 less in the budget (camera + EF adapter). Personally I would love one for portrait and landscape work, but I can not justify the expense. I suspect I'd get more use from that tamron 150-600 and a new tripod.
5D3, 5D2, 40D; Various lenses

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #66 on: May 04, 2014, 11:56:42 AM »
Glancing at his gear wish list, it looks like he's more into action than astro. An A7R is 2500 less in the budget (camera + EF adapter). Personally I would love one for portrait and landscape work, but I can not justify the expense. I suspect I'd get more use from that tamron 150-600 and a new tripod.

I'm actually pretty into astrophotography. It splits my budgets now. The A7r, along with pretty much any Sony camera, Nikon camera (with the exception of a couple that use different sensors), and a lot of other cameras that use Sony sensors (i.e. Pentax) are all pretty poor choices for astrophotography. Those manufacturers all mess with the image signal pretty heavily.

They clip the black point, rather than using a bias offset (Canon uses a bias offset). That causes two problems for astrophotography: By clipping to the black point, you simply eliminate a lot of the dimmer background stars entirely, they are gone from the signal, unable to be retrieved; They make it difficult to use standard bias frame calibration techniques to remove any noise caused by sensor bias and recover those dim stars (which IS possible with Canon cameras.)

Sony/Nikon/Pentax/etc. also tend to apply noise reduction to the RAW signal in hardware...an unconfigurable noise reduction, that's just always applied. Having total control over noise is a pretty critical facet of astrophotography...the vast majority of images you create for astrophotography have image data only in the lowest echelons of the signal, stars are the only things that have levels throughout the signal. While you can do some pretty amazing things with the D800 at ISO 100 when it comes to lifting shadows, that's nothing compared to the kind of lifting you do in astrophotography. The D800 can be lifted about six stops. In astrophotography, your often lifting by a lot more than that...to really pull out dust lane detail and dark nebula detail and things like that, it's common to lift things by an equivalent of 10-15 stops! Not even the great D800 or any other Exmor DSLR camera can handle that, in part because of the black point clipping, which is throwing away a couple/few stops of potentially recoverable information in the first place.

A proper astro CCD camera has at least 18-19 stops of dynamic range, and usually well over 20 stops. They are thermally regulated (anywhere from -40°C to -80°C Delta-T from ambient), which nearly eliminates dark current noise, generally have relatively low read noise, usually have much higher Q.E., and usually have larger pixels (smaller astro CCD sensors usually have around 5-6µm pixels, larger astro CCD sensors usually have 9-24µm pixels; FF DSLRs tend to have pixels in the 6-7µm range, and APS-C DSLRs are now around 3.5-4.5µm). Since astro CCD sensors are also most often monochrome, and you usually image in LRGB (luminance + RGB), you can produce images with much stronger signals than you can with bayer-filtered DSLRs.

So, while I'd like an A7r for my landscape photography, it is actually one of the worst possible choices for astrophotography. I do landscapes sometimes, wildlife and birds most of the time, and astrophotography every time there is a clear night. Since Canon cameras don't mess with the image signal nearly to the degree that other manufacturers to (they do some response curve tweaks at certain higher ISO settings, but I usually image at ISO 400, which Canon pretty much leaves alone), and since the 5D III can be used for landscapes (it has a very respectable pixel count and frame size for that), wildlife and birds (it meets my minimum expectations for rate at 6fps), AND can be used for astrophotography, it's a far better investment in the interim (especially with prices hitting $2700 pretty regularly now.) It may not have the DR of the A7r, but it is a vastly more versatile device.

If it wasn't for the astrophotography, I'd get a 1D X. By getting a 5D III, that leaves me plenty of cash to invest in a proper astro CCD, a filter wheel and filter system, and a few other accessories.

So...given how versatile Canon's DSLRs already are...do they really need to become a Sony clone with their new sensors?  ;D :P
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

canon rumors FORUM

Re: More Sensor Technology Talk [CR1]
« Reply #66 on: May 04, 2014, 11:56:42 AM »

3kramd5

  • Canon 70D
  • ****
  • Posts: 315
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #67 on: May 04, 2014, 11:59:49 AM »
Are you using telescopes for astro or the 600?
5D3, 5D2, 40D; Various lenses

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #68 on: May 04, 2014, 12:38:26 PM »
Are you using telescopes for astro or the 600?

Currently using the 600, however this baby is at the top of my list:

Astro-Tech 10" f/8 truss tube Ritchey-Chrétien optical tube

Telescopes are kind of like lenses, though. You usually need a few. The 600 is ideal for wider field work. I think the 200mm f/2 L would be an excellent one for very wide field work, but I think when I get the 300/2.8 L II that will be the last Canon supertele for a long while. The 300 is still excellent for wide field work. The 10" RC is a longer focal length, which is better for galaxies and clusters, and for close-up work of parts of nebula.

« Last Edit: May 04, 2014, 12:40:43 PM by jrista »
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

3kramd5

  • Canon 70D
  • ****
  • Posts: 315
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #69 on: May 04, 2014, 11:28:59 PM »
Nice. That's quite an apparatus. My only experience (about 7 years of engineering design work) with telescopes is with a rather different variety, unless you're into IR.

5D3, 5D2, 40D; Various lenses

GaryJ

  • PowerShot G1 X II
  • ***
  • Posts: 63
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #70 on: May 05, 2014, 03:30:59 AM »
The more you post, jrista, the more I respect you.
+1
7D,6D,100mmL IS f2.8 Macro,70-300mm L,MPE-65, 24-105 f4 L,50mm f1.8,70-200mm L f4,Siggy 150mmf2.8 Macro, Tokina 11-16mm Kenko Extenders and 1.4 TC [for 70-300]

Stu_bert

  • EOS M2
  • ****
  • Posts: 204
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #71 on: May 05, 2014, 06:06:42 AM »
Glancing at his gear wish list, it looks like he's more into action than astro. An A7R is 2500 less in the budget (camera + EF adapter). Personally I would love one for portrait and landscape work, but I can not justify the expense. I suspect I'd get more use from that tamron 150-600 and a new tripod.

So, while I'd like an A7r for my landscape photography, it is actually one of the worst possible choices for astrophotography. I do landscapes sometimes, wildlife and birds most of the time, and astrophotography every time there is a clear night.


I was looking at the A7R with adapter for landscapes, but then I read on Thom Hogan's site that Sony uses lossy compression on their RAWs (unless I misread him), and you can't switch it off!

Why would they do that?   :( :(

On that basis, it may have amazing DR but then it surely will just smudge out some of the detail for err, actually I'm not sure for what benefit...

Had a look at that astro link - it's a whole new language there  :) If I understood correctly, then it's a 2000mm lens? And optically is it better than your 600mm lens with a 1.4x and 2.x attached? Just curious as to the benefits. Thanks.
If life is all about what you do in the time that you have, then photography is about the pictures you take not the kit that took it. Still it's fun to talk about the kit, present or future :)

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #72 on: May 05, 2014, 11:32:36 AM »
Glancing at his gear wish list, it looks like he's more into action than astro. An A7R is 2500 less in the budget (camera + EF adapter). Personally I would love one for portrait and landscape work, but I can not justify the expense. I suspect I'd get more use from that tamron 150-600 and a new tripod.

So, while I'd like an A7r for my landscape photography, it is actually one of the worst possible choices for astrophotography. I do landscapes sometimes, wildlife and birds most of the time, and astrophotography every time there is a clear night.


I was looking at the A7R with adapter for landscapes, but then I read on Thom Hogan's site that Sony uses lossy compression on their RAWs (unless I misread him), and you can't switch it off!

Why would they do that?   :( :(

On that basis, it may have amazing DR but then it surely will just smudge out some of the detail for err, actually I'm not sure for what benefit...

Hmm, I hadn't heard of that. If they do, it's foolish, and you really no longer have a RAW image. I am a bit skeptical of that...it doesn't seem logical, but who knows.

Had a look at that astro link - it's a whole new language there  :) If I understood correctly, then it's a 2000mm lens? And optically is it better than your 600mm lens with a 1.4x and 2.x attached? Just curious as to the benefits. Thanks.

Reflecting light tends to produce superior spots at the sensor plane in comparison to refracting light. Reflecting light can warp star diffraction spots due to coma and astigmatism, but that's about it. Refracting light, on the other hand, suffers from all forms of optical aberrations...which also includes chromatic aberrations, spherical aberration, etc. The RC, or Ritchey-Chretien, telescope design is one of the more superior designs. It's the same design used in all the major earth-bound telescopes...the huge ones, up to 10 meters in size. It tends to produce superior results, although it does suffer from some coma and astigmatism in the corners.

There is a better telescope design than even the RC, called a CDK or Corrected Dall-Kirkham. The CDK uses a mirror and built in corrector to get one of the best spot shapes, center to corner, of any telescope design I've ever seen. PlaneWave makes CDK scopes, but they are pretty pricey. From what I've read and seen, a CDK is about the best telescope design in the world today.

As good as my lens is, and it is very good with a very flat field corner to corner, it is no RC and certainly no CDK. If I throw on teleconverters, that gets me more focal length (which is not necessarily the best thing...a LOT of nebula are even larger than I can fit in my field with the 600mm, let alone a 2000mm scope), but  it also increases the optical aberrations. For galaxies, clusters, and getting close up on parts of nebula, a longer, better scope like the Astro-Tech 10" RC is better. The larger aperture, ten inches vs. six inches, also means I can resolve smaller magnitude stars, galaxies, and other details. Most scopes work with focal reducers, so while it is 2000mm natively, I can use a 0.63x reducer to make it an f/5 1260mm telescope. That is relatively fast with a moderately wide field. For planetary work, I can also throw on a 2x or 3x barlow lens, and get a 400mm f/16 or 6000mm f/24 scope, which is much better for planetary imaging (f-ratio doesn't usually matter for planetary, as you image planets by taking videos with thousands of frames for anywhere from a couple minutes to as long as a half hour...then filter, register, and stack the best frames of the video, which is basically performing a superresolution integration...that eliminates blurring from seeing, and effectively allows you to image well beyond the diffraction limit.)
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

canon rumors FORUM

Re: More Sensor Technology Talk [CR1]
« Reply #72 on: May 05, 2014, 11:32:36 AM »

NancyP

  • EOS M2
  • ****
  • Posts: 197
    • View Profile
Re: More Sensor Technology Talk [CR1]
« Reply #73 on: May 05, 2014, 01:03:53 PM »
Very dangerous, jrista, very dangerous. Astrophotography is like boating - you start out with a $300.00 (slow) toy kayak, you end up wanting an America Cup yacht. I am at the toy kayak stage, and likely to stay there. A combination of living in the center of a "white" zone (central city to the rest of you), having a day job, no longer having the ability to easily adapt to swing schedules, and living in an often cloudy location (St. Louis MO) make serious application to astrophotography difficult. I can learn a bit at our local astronomy park, 45 minutes away in an "orange-soon-to-be-red" zone. High quality darkness is about 2.5 to 3 hours away at minimum.

Hats off to you for taking on PixInsight.

I am still drinking the Sigma DP#M koolaid because the color subtlety is very suitable for landscape, and the camera weighs ~300 grams including an aluminum L bracket/grip and can be well supported by a 1600 gram tripod/head/QR kit. Pop some extra batteries, filters, and "nodal" slide in my pocket, and I have a great fast-hiking compatible landscape kit.

jrista

  • Canon EF 300mm f/2.8L IS II
  • *******
  • Posts: 3746
  • POTATO
    • View Profile
    • Nature Photography
Re: More Sensor Technology Talk [CR1]
« Reply #74 on: May 05, 2014, 01:20:46 PM »
Very dangerous, jrista, very dangerous. Astrophotography is like boating - you start out with a $300.00 (slow) toy kayak, you end up wanting an America Cup yacht. I am at the toy kayak stage, and likely to stay there. A combination of living in the center of a "white" zone (central city to the rest of you), having a day job, no longer having the ability to easily adapt to swing schedules, and living in an often cloudy location (St. Louis MO) make serious application to astrophotography difficult. I can learn a bit at our local astronomy park, 45 minutes away in an "orange-soon-to-be-red" zone. High quality darkness is about 2.5 to 3 hours away at minimum.

I know a lot of imagers who shoot under red and white zones. Have you ever looked into a Light Pollution Reduction/Suppression filter? There are a number of them. I'm in a yellow zone myself, but I still use the Astronomik CLS filter myself (I prefer shooting nebula, if you shoot galaxies, lp filters are a mixed bag). You could also look into doing Narrow Band imaging...with NB, you block out a ton of light except the one (or three) very narrow bands your interested in. You need longer exposures, but NB works extremely well under red and white zones, and I've seen some stellar work from people in some of the most heavily populated places in the eastern half of America.

Hats off to you for taking on PixInsight.

PI isn't so bad once you get used to it. It has a funky way of doing things until you learn why...then you realize how incredibly awesome it is. ;) I also recommend it if you image under light polluted skies. It's DBE or Dynamic Background Extraction script can help you extract light pollution from your background skies and flatten it, and can do so if you use LPR filters or not.

I am still drinking the Sigma DP#M koolaid because the color subtlety is very suitable for landscape, and the camera weighs ~300 grams including an aluminum L bracket/grip and can be well supported by a 1600 gram tripod/head/QR kit. Pop some extra batteries, filters, and "nodal" slide in my pocket, and I have a great fast-hiking compatible landscape kit.

For those who understand what Sigma Foveon cameras offer, I say more power to 'em! There is no question the color fidelity is extremely high with Foveon sensors. The light weight is also pretty nice for when you gotta hike to your vistas. That's one of the reasons I like the idea of an A7r for landscape photography...but the camera overall is just...not general purpose enough to justify the cost.
My Photography
Current Gear: Canon 7D | Canon EF 600mm f/4 L IS II | EF 100-400mm f/4.5-5.6 L IS | EF 16-35mm f/2.8 L | EF 100mm f/2.8 Macro | 50mm f/1.4
New Gear List: Canon 5D III/7D II | Canon EF 300mm f/2.8 L II

canon rumors FORUM

Re: More Sensor Technology Talk [CR1]
« Reply #74 on: May 05, 2014, 01:20:46 PM »