New member - New DCS 720x!

Discuss older Nikon-based Kodak digital SLRs, including DCS 100, DCS 200, NC2000, DCS 400/600/700-series, etc. Ask questions, post general comments, anecdotes, reviews and user tips.
Post Reply
ondebanks
Posts: 10
Joined: Fri Jul 15, 2011 8:48 pm
antispam: No

New member - New DCS 720x!

Post by ondebanks » Tue Aug 16, 2011 5:24 pm

Hi folks!

Just got my registration activated at last (thanks Jarle!). This is my first post. I've read a lot here already.

I think a quick personal photographic history is in order, by way of introducing myself. The first "real" camera I ever picked up and used was my older brother's Nikon F301 in 1986 - I was just 15. I got the photo bug and instantly wanted to employ it for my even older passion, astronomy. Ever since, astrophotography has been the perfect blend of the two fields I love. But god has a sense of humour, so he ensured I was born in the cloudiest country on earth (Ireland). :(

I built up my own Minolta manual focus system from 1988 on (X300, added an SRT101, then traded the X300 up to an X700). It was great, but I traded it all in for a Mamiya 645 medium format kit in 1992. I intended to never use "small format" cameras again, but found myself missing photo opportunities for lack of a small pocketable camera, so I got an old Rollei XF35 in 1995. Then a new Canon EOS 500n in 1998, which was just convenient for travelling abroad with my girlfriend. By the early 2000s, we'd settled down, bought a house and our careers were going well, so I started to get those things I'd put off through my 9 years of graduate studies and mobile contract postdoc jobs. Telescopes and heavy duty equatorial mounts, more medium format gear. I went through a Kiev/Pentacon/CZJ 6x6 phase from 2003-06; a Praktica VLC/M42 phase in 2005-06; resumed steadily adding to my Mamiya 645 system from 2006 on; added a Mamiya Universal Press 6x9/Polaroid phase from 2007-10 and even dabbled with Toyo 4x5 stuff and adapting other leaf-shutter lenses; and finally "went digital" with a Kodak DCS 645M back and Mamiya 645AFD in March 2010. Apart from our 2005 Canon Powershot A630 and camera-phones, I'd never owned a serious digital camera before 2010 - many people find that hard to believe!

Anything I buy, I research to death beforehand. When I finally made my move on ebay for the Kodak DCS 645M back, I knew more about medium format backs and their sensors than many dealers of such backs! Coming late to the game, I took to it with gusto and am now quite passionate about sensor characterisation etc. You should see my spreadsheets... :wink:

Now of course, one cannot join the Kodak DCS family without becoming aware of all its members. Those converted Nikon F5s looked mighty purty. So while the 16.7 megapixels, 36.7 x 36.7 mm DCS 645M is my beloved good-light-high-quality digital system, I had an itch for something else to complement it: instantly responsive, high ISO, quick AF, rapid shooting of my kids etc. Even better if it would also be a great astro-camera. And of course take my 645 lenses on an adapter. So the high sensitivity 2MP Kodaks looked interesting. I also crave interchangeable viewfinders (pretty standard in medium format SLRs), drop-in focus screens, and traditional mechanics like real mirror lock-up, so the modularity of the Nikon F5 body is great. It didn't take me long to see that the DCS 720x, the last of the line, was the one for me.

So I put some ebay sales proceeds into starting a DCS 720x system. First, an ebay auction bagged me a DCS 720x body with prism, IR filter, caps and straps, yay! €210, not bad, although the charger cost me €115 more (if I'd waited another week I could have got one for around €50 with a beat-up DCS 620 - several were listed by an Austrian ebayer). Then for small change, I bought a brace of cheap batteries; a couple of PCMCIA-CF adapters for my CF cards; and a Nikon T-ring to use my M645 lenses on my Zoerk M645-T adapter. All the pieces had arrived by Monday of last week and I started testing it. My plan is to see how it performs, with my M645 lenses for starters. If I like it (and so far I am liking it a lot!), and if it passes my sensor tests, I'll get a used Nikon 50/1.4 D lens for the fast AF and superfast aperture. And an F5 6x magnifying vertical viewfinder for astrophotography. AFAIK there isn't, and hasn't been, any other DSLR which can do that.

Ray

Webmaster
Site Admin
Posts: 1005
Joined: Fri May 20, 2005 4:12 pm
antispam: No
Location: Norway
Contact:

Re: New member - New DCS 720x!

Post by Webmaster » Wed Aug 17, 2011 11:49 am

Welcome to the forum. Not sure I would use the 720x for any serious astrophotography, but if it works, it works! Hard to believe you have more clouds in Ireland than we do here in Norway, but I guess anything is possible :-)

Personally, I use a small Orion SkyView Pro 127 Maksutov-Cassegrain attached to various Nikon bodies, as seen here: http://www.nikonweb.com/svp127. Great telescope, but obviously not suitable for deep sky and other dim objects.

Jarle

ondebanks
Posts: 10
Joined: Fri Jul 15, 2011 8:48 pm
antispam: No

Re: New member - New DCS 720x!

Post by ondebanks » Wed Aug 17, 2011 2:23 pm

Jarle, where in Norway are you? In the south of Scandinavia you tend to get at least some continental high-pressure systems, which keep the clouds at bay. In Ireland we are too far removed from the continent to get these. Have a look at http://home.cc.umanitoba.ca/~jander/clo ... louds.html - the cloud stats are grim here on the west coast of Ireland!

You've got some lovely photos with the 127 Mak-Cass! Lunar resolution is excellent with the afocal shots.

> Not sure I would use the 720x for any serious astrophotography, but if it works, it works!

Despite my moaning about clouds, last night was actually 80% clear - very rare in this poor summer of 2011. So I got out and took some test shots. The very bright moonlight didn't help but I was allowing for that in my assessments.

- Turns out that the 720x has disappointingly high dark current. I was never expecting Canon CMOS performance here, but even for a CCD it's high; Kodak's KAF-2002CE datasheet claims "low dark current" but that "low" is a function of both the usage context and the design era (October 2000). With dark-frame subtraction enabled, 10 seconds was fine, but things got nasty beyond 20 seconds. 1 minute exposures are unusable. What's happening is that the sensor is heating up further while it's taking the dark frame, so although the time is equal, the dark current is not (the datasheet says it doubles with every 6.3 degrees C rise in temperature), and it over-subtracts.
- A side effect of the high dark current is that the camera also seems to be over-estimating the "bias level" of the CCD in longer exposures - it uses additional masked off pixels outside the light-sensitive area to measure this level, but those pixels also have dark current, so their mean level rises in long exposures too. I've also seen this effect in my DCS645M, but to a lesser extent. I wish that Kodak's firmware for all these cameras didn't subtract the bias level from the RAW frames, and did it instead in PhotoDesk. Kodak are emulating Nikon here, and unfortunately not emulating Canon. If RAW was truly RAW with no offsets subtracted, then dark frames could be taken separately and subtracted from the images later, choosing from a range of temperatures and exposure times.
- The firmware abruptly terminates CCD capture in exposures beyond 1 minute. (The shutter stays open for the commanded duration, but the screen displays "Capture Error! Image was not saved"). I get exactly the same thing on my DCS645M, on the stroke of 60 seconds, so I use a timer-release set to 59 seconds. I never knew whether it was the Mamiya body or the Kodak back which was to blame, but now I know it's the back, since another Kodak DCS product behaves identically. Now this is pretty moot, given that the dark current makes going longer than 1 minute pointless anyway. But it's another slap on the wrist for Kodak's firmware. It's very nice that they allowed the F5 Custom Functions to be described in human language and set in their menu system, but why bother with the Custom Function which enables exposure times out to 30 minutes, when your own firmware kills it at 1 minute?

BTW my current camera firmware = 3.2.8, the final version, and I've also tried the penultimate version still on Kodak's website, and it behaves the same.
Does anyone have a copy of older DCS 7** firmware?? Please let me know!

Those are the negatives. The positives are that:
- With the IR filter removed, infinity focus on my M645 adapted lenses is exactly infinity focus for the camera. The User Guide hinted that this would be the case, but Kodak were coy about explicitly saying that the "natural" focus condition for the DCS 7** is without any internal filter, and using an IR/AA filter causes focus to shift. But having the filter ahead of the viewfinder and AF systems means that the focus shift is self-correcting.
- The spectral response is "perfect" for astronomy. As expected from the CCD datasheet, which reproduces the widely publicised spectral response plot featured in the Kodak press release when the DSC620x came out, H-alpha (the 656 nm light that makes nebulae glow red) is strong, far better than any stock unmodified DSLR. The cost of modifying a regular DSLR to get this better response is about what I paid for the DSC720x, but then you cannot re-sell a modified camera back into the regular photo market, as the mod is irreversible (or at least, undoing it costs as much again!). Should I ever sell my DSC720x, it will be as good and as saleable as the day I got it.
- Speaking of deep red sensitivity, one of the other things that drew me to this camera was the CMY instead of RGB Bayer array...I seem to be the first person to realise that 3 of the 4 pixels receive H-alpha light in a CYMY sensor, instead of just 1 of the 4 in an RGBG sensor. The standard CMY->RGB conversion probably doesn't fully exploit this fact, so I am going to play with the RAW file channels and also try red filtration, to see if I can do better.
- I've just run some Roger Clark-style sensor tests on the one I got, and I'm getting readout noise of 16 e- (the Kodak KAF-2002CE datasheet indicates 15 e-) which is good for a fast-readout CCD...any recent CMOS camera is considerably better though. Still, I'm happy that the camera is hitting the CCD datasheet spec for readnoise, which is specced for nominal 4 MHz readout (this would be 2 frames/sec max with fast shutter speed) even though the camera is actually reading out at the CCD's maximum pixel shift rate of 10 MHz (the rate needed to support 5 fps max).

And the neither-positives-nor-negatives are:
- These tests also showed that gain and readnoise DO NOT change with ISO setting! So ISO seems to be just a tag on the RAW file for the benefit of the conversion software - like with some MFDBs. It is a little disappointing that the ADC is not optimized as ISO rises (or perhaps the ADC could not do any better, and the 15/16 e- represents the "noise floor" of the sensor itself), but OTOH it means that the full scene dynamic range is ALWAYS available in the RAW file, even at stupid high ISOs! When you set higher ISO on a regular DSLR, you are (usually) clipping highlight signal in a trade-off for lower readout noise in the shadows. When you set higher ISO on the DCS cameras you are just underexposing; the highlights are still there and in fact they are extended by as many stops are you are underexposing, and the readout noise is the same.

So, the next steps are
- See how it performs under a dark sky with no moon
- Investigate getting the maximum from that high H-alpha sensitivity
- Look into possible ways of cooling it, to reduce the dark noise.
Until I've done additional things like this, I'm keeping an open mind on it.

It might seem like I'm putting an awful lot of weight on its astro-suitability, despite the lack of clear sky opportunities to actually do astro-photography. I'll shoot a lot more photos of my family and friends than of celestial objects, so why the hang-up about the latter? That is a conundrum which has influenced every camera purchase I've made! I have two wishlists which can sometimes compete with each other - camera/system features that I enjoy and cherish, like fast lenses and interchangeable finders; and astro-suitable performance. In my film days it was easier - film choice primarily determined astro-suitability, and that was separate to camera choice. Now with DSLRs, the two are tied together, and compromises are necessary. I could get an extremely low noise CMOS DSLR modified for astrophotography, but I would never love it. Ah, how often the heart over-rules the head!

Ray

Stan Disbrow
Posts: 569
Joined: Fri May 20, 2005 7:33 pm
Location: Raleigh, NC USA

Re: New member - New DCS 720x!

Post by Stan Disbrow » Wed Aug 17, 2011 10:32 pm

Hi,

I use three DCS cameras. The 560 with Canon AF as well as Leica, Zeiss and Nikkor manual focus ones via adapters. The 760c for most things. And, the 720x for low-light, high-speed shooting - mainly night auto racing, but also indoor bowling without flash.

The 720x is still the best option for what I use it for. I'm not sure it's the best choice for slow, long exposure work. It does have a lot of noise when used that way.

The thing has a tendency to yellow cast it's photos, and I find the Kodak's own PhotoDesk raw converter handles that best, still.

The CYM CFA is to remove one layer of dye over the photosites. An RGB CFA has two layers, of course. It was an odd thing to do at the time, and still is. It's where the yellow cast comes from, of course. Using yellow instead of green for the luminance channel. ;)

I have been thinking about a medium format with a Pro Back Plus for a while, and also about a Leica R9 and DMR. Both options are still fairly far down on the list of what I want t spend money on at this point. An MF system would probably come before a Leica one. Leica lenses are always costly!

Later!

Stan
Amateur Photographer
Professional Electronics Development Engineer

ondebanks
Posts: 10
Joined: Fri Jul 15, 2011 8:48 pm
antispam: No

Re: New member - New DCS 720x!

Post by ondebanks » Thu Aug 18, 2011 11:33 am

Stan,

Interesting that you use both a 560 and a 760c. I would have thought that they overlap to such an extent that only one would be needed.

You should, if you can, get a Pro Back. Very different beast to Leica digital, but unless you have that mysterious 6th sense that some people claim to have for the images delivered by Leica optics (to me, they look no different to any other great optics), you'll find it delivers just as good quality, at lower system cost, but higher system bulk.

I'm just wondering, why are you thinking of the Pro Back Plus, rather than the Pro Back 645? They both have the same sensor, but some things are better in the PB 645 and in the systems that it attaches to. Smaller crop factor, autofocus and manual focus confirmation, faster lens apertures, PASM modes, lens EXIF metadata, to name a few things you get with the PB 645 on a Mamiya 645AFD/Contax 645/Hasselblad H, and don't get with the PB Plus on a Mamiya RZ67/Bronica SQ/Hasselblad V. And if you really love the Hasselblad V Zeiss lenses, you can use them on the 645 bodies as well with adapters. You can even use the Bronica SQ lenses on the Mamiya 645AFD with an adapter.

None of these 645 systems is perfect - but you can find the best compromise within them. Mamiya, very annoyingly, "did a Nikon F6" and dropped the interchangeable VFs from the 645AF(D) design. But OTOH they have the largest, fastest, and most affordable range of MF, AF and adapted 3rd-party lenses of the lot, and that has always swung it for me. The Contax would be my 2nd choice: best ever medium format body for film, but not quite so well integrated with digital as the Mamiya or Hasselblad H. Kodak Camera Manager cannot drive the Contax from a computer, for example, but it can drive the Mamiya and Hasselblad.

The Kodak user interface and screen on the PB 645 are almost identical to the DCS 7**, by the way, so the transition would be rather easy for you. The only differences I can see are that the DCS720x has added Nikon's Custom Functions to the menu, while the PB 645 has another top menu "tab" called "Status" to call up the same sort of info (battery, shots remaining, ISO, PC connection...but oddly no White Balance) that the DCS720x has at all times on its separate lower LCD. Also, the only way to change ISO on the PB 645 is via the "Main Menu".

Cheers,
Ray

Stan Disbrow
Posts: 569
Joined: Fri May 20, 2005 7:33 pm
Location: Raleigh, NC USA

Re: New member - New DCS 720x!

Post by Stan Disbrow » Thu Aug 18, 2011 10:22 pm

Hi,

I used to have both Canon and Nikon systems. The Canon was AF for sports shooting and the Nikon was MF for other things. The way that came about, was I started with Nikon manual focus stuff in the 1970's and kept it around, not being interested in their auto focus with the shaft drives. Then, I found out that the Canon AF stuff mostly used in-lens servo-motors and got hooked. This was all film, of course.

When I went digital, it was originally with a Nikon E2, then a D1. It was odd then, as I wound up with a few Nikon AFS series lenses for the digital. The E2 worked with the Nikon MF glass, and the Canon stuff sat as it was all film. Until the 1D came out, then the 1Ds. Along the way, the Kodak 560 prices dropped such that I got one of those and liked the Kodachrome aspect of the dyes Kodak used in their CFAs. I actually sold my 1Ds for the 560 because I could do well enough with the Kodak's 6 MP.

I added the 720x when they still cost quite a bit, but wanted that lower-light capability for certain sports situations: night auto racing and no-flash-allowed indoor bowling. There was a point where all I had was the 560 and the 720x and some duplication in lenses because of the two systems.

Eventually, I picked up a 760c for $500 and so had the newer sensor over the 560 and could reduce my Canon lens collection that duplicated what I had in the Nikon. By then, I had a set of lenses with adapaters for use on the 560 that meant I might as well keep it around. :)

The Leica comes not from wanting so many of their lenses over the good old Nikkor manual ones I have, but for the fact that the DMR uses the 10MP 4th generation Kodak sensor. I think it's even one turn of the development crank beyond the latest of the Pro Back ones. The 10MP APS-H sensor was a full 16-bit dynamic range unit, and I'd really like to have the extra bits.

Anyone know if the sensor in the Pro Backs ever wound up with 16-bit DR?

I refer to the Pro Back Plus meaning the latest sensor design, but would go for a 645 medium format version of it. I never did figure out if I would want a Mamiya or a Contax 645, but your notes on the systems sound like you've been down that whole road. Mamiya sounds just fine to me.

In the end, I'd want what I have, plus an R9/DMR and a 645 with a Pro Back on it. Then, I'd have all sorts of options! It's a matter of the prices being right these days. I'm long out of the time when I'd drop several thousand bucks on the newest digital whatnot. I can do most everything with the three DSLR bodies I have, but there are times when I'd really like the high-res square image a 645 Pro Back would provide. :)
Amateur Photographer
Professional Electronics Development Engineer

ondebanks
Posts: 10
Joined: Fri Jul 15, 2011 8:48 pm
antispam: No

Re: New member - New DCS 720x!

Post by ondebanks » Thu Sep 01, 2011 3:44 pm

Stan,

Thanks for sharing your story.
Stan Disbrow wrote: The Leica comes not from wanting so many of their lenses over the good old Nikkor manual ones I have, but for the fact that the DMR uses the 10MP 4th generation Kodak sensor. I think it's even one turn of the development crank beyond the latest of the Pro Back ones. The 10MP APS-H sensor was a full 16-bit dynamic range unit, and I'd really like to have the extra bits.

Anyone know if the sensor in the Pro Backs ever wound up with 16-bit DR?
The Kodak backs were only ever 12-bit output (although one piece of Kodak literature I found says that the analog signal path is 16 bit, I guess implying that it only becomes 12 bit at the last step of writing the output to file).
However, the same Kodak sensor (KAF-16802CE) was used in other backs like the PhaseOne P20/H20, which are supposed to be 16-bit. But then you are getting into a different user interface, different software, higher prices (especially for repairs and parts), and non-removable IR/AA filters.

As a general guide, Kodak sensors were/are used in medium format backs/cameras by Kodak themselves, PhaseOne (up to the P45+), Imacon/Hasselblad, Leica and Pentax.
Dalsa sensors are/were used by Leaf, Sinar, Mamiya, and the latest PhaseOne backs (P40+, P65+, IQ range).
The ironic thing is that Kodak owned Leaf, but Leaf used Dalsa sensors, not Kodak ones! Go figure.
I don't really like the Dalsa sensors - for a given generation (pixel size), they have generally lower quantum efficiency, somewhat higher readout noise (although their latest ones are as good as Kodak), and much higher dark noise.

You're right - the 10MP Leica DMR and M8 do indeed use a later-generation sensor to the 9 micron Pro Backs; they are part of the 6.8 micron family from 2004. Their brethren include the 44x33 mm KAF-31600 with microlenses (used in the superb Phase One P30+, and Hasselblad H3D-31) and the 48x36 mm KAF-39000 without microlenses (used in the Phase One P45+, and Hasselblad H3D-39 and CFV-39).

Ray

Post Reply