The P45+ back, what's so special?

[Shashin]

However, is it true that hour long exposure hits up the sensor and eventually might damage the digital sensor?

Sounds like an urban legend to me, probably started by a film astrophotographer.

 

[Shashin]

Not sure what Pentax is doing to allow longer times/less noise as I have never shot the P645, however I have worked with a few night shooters who have and their results were very impressive. From my understanding, the Pentax and P45+ ue the same Kodak chip.

Paul

Could simply be the difference in signal processing. Folks like to talk about chips like film having inherent qualities. And to a point they are right. But there is a lot of other things that happen. So the Pentax could be getting better images than the P45+ simply because of signal processing.

 

[dougpeterson]

I'm surprised this thread only brings up one differentiator.

Obviously I'm very biased, but from my point of view there is really only one thing shared between an H3D-39 and a P45+: the sensor.

That's like discussing a Nikon and Sony that use the same sensor and assuming that they are nearly identical except for a few brand-specific features.

You'll want to get some H3d-39 pros from a Hassy expert/user/dealer, but here are a few pros of the P45+:
- as mentioned many times above, great long exposures
- extremely simple four-button user interface, fast to learn
- easy to use with gloves on
- built in battery allows user on tech/view camera without any additional external accessories or power source
- extremely rugged chassis with proven performance in a huge range of environments (very cold, very humid, very hot)
- raw files can be processed in Capture One which has an enormous range of tools and is, in fact, the preferred raw processor of many Nikon and Canon users.
- extremely consistent capture speed for either CF or tethered capture
- tethering is supported in Capture One side-by-side with Canon/Nikon etc
- support/training from Value Added dealers such as ourselves and other reputable dealers (assuming you buy from a dealer)

There is also the whole issue of open vs. closed platform. Depending on your needs this may be a non-issue or a big deal. Any P45+H back can be used on any H2 or H4X, so a backup/loaner of either the body or back can be had from any major rental house anywhere in the world, and a replacement can be purchased second hand from eBay, a dealer, etc and be used right away at no additional cost or time. An H3D-39 back (aka digital magazine) are electronically paired and if you want to replace, upgrade, borrow, or bring a backup then you must either acquire a matched paid (back+body), or have the component paired by Hasselblad.

Phase One also offers a platform swap where you switch your back to another platform (unless covered by your warranty this is $3k). That means if in the future you decide you need/want a different body (e.g. Contax, Phase One DF, future Phase One body, Hassy V, etc) the majority of your investment is held, and you won't have to learn new software/back.

Also, it's not true that there are no warrantied used P45+ units anymore. Certainly most end-users' systems will have no warranty left, but we, Digital Transitions, (and presumably other dealers) do have P45+ units with warranty remaining.

Also, lens corrections for most Hasselblad H lenses are included in Capture One, and from my experience the chromatic aberration removal and purple fringing removal are better in Capture One for a P1 back than they are for any other camera+software system, including when using a P1 back on a H body.

As I said, I'm biased (my employer, Digital Transitions) and the H3D-39 is a good tool, so ideally you'll want to get your hands on both. Many dealers such as us offer evaluation rentals whereby you get 100% of the rental counted towards a purchase.

My main point was that the thread seems to have gotten stuck on a very specific advantage, and ignored that the two backs are really quite different. Each has some notable advantages/disadvantages and for-sure the price difference provided by supply-demand on the used market is not 100% explained by long exposures alone. Similar price discrepancies can be found for other similarly competitive backs: look up pricing for the Mamiya ZD, Aptus 22, Sinar 54M, Hasselblad H2D-22, and P25 - they are all 22mp and the price spread on the used market can be quite dramatic.

 

[dougpeterson]

From my understanding, the Pentax and P45+ use the same Kodak chip.

This is not correct. The Pentax uses a KAF-40000 sensor. The P45+ uses a KAF-39000 sensor.

 

[dougpeterson]

Could simply be the difference in signal processing. Folks like to talk about chips like film having inherent qualities. And to a point they are right. But there is a lot of other things that happen. So the Pentax could be getting better images than the P45+ simply because of signal processing.

Who said Pentax is getting better images than a P45+? Or are you talking here specifically about higher ISOs? In which case there is no argument - the P45+ is not (and was never advertised as) a high-ISO back.

At low ISOs I've never seen any compelling example of a Pentax file which exceeded a P45+ file. Do you have such an example to share?

 

[JorisV]

Also, lens corrections for most Hasselblad H lenses are included in Capture One

6 out of 11 lenses are covered, it would be more accurate to say that the most common H lenses are covered...

 

[yaya]

I've been looking at 39mp backs for the H series and what constantly surprises me is the price of the P45+

Why is it so high relative to an entire H3DII 39 system? Especially as they are the same sensor. Based on used prices the H3DII is 30% less. Has lens corrections and enhancements via Phocus etc?

One product is still available new with warranty in different mounts, the other one is discontinued

 

[Shashin]

Who said Pentax is getting better images than a P45+? Or are you talking here specifically about higher ISOs? In which case there is no argument - the P45+ is not (and was never advertised as) a high-ISO back.

At low ISOs I've never seen any compelling example of a Pentax file which exceeded a P45+ file. Do you have such an example to share?

Doug, before you jump down my throat, perhaps you want to reread my post which was simply a comment on Paul's comment on the sensors. If you read carefully, you would see that I just suggested the Pentax files "could" be better because of signal processing. I did not say it was better. The point of my comment was that there is more to a final image than the sensor.

Man, you need to take a break on the weekends and get out of the office.

 

[dougpeterson]

Doug, before you jump down my throat, perhaps you want to reread my post which was simply a comment on Paul's comment on the sensors. If you read carefully, you would see that I just suggested the Pentax files "could" be better because of signal processing. I did not say it was better. The point of my comment was that there is more to a final image than the sensor.

My apologies. I simply misread what part of the sentence "could" applied to when you wrote:
"So the Pentax could be getting better images than the P45+ simply because of signal processing."

You meant "if there is a difference it could be because of signal processing".

I read "the difference could be because of signal processing"

 

[Uaiomex]

I need to revive this thread since I'm seriously thinking on acquiring a used P45+.
I'm concerned about this particular post in which some P45+ backs were manufactured without the capability of one hour long exposures due to a different controller card.
Not that I'm saying that this is not true. It's just that I haven't heard a confirmation word from the people that sell this equipment.

Eduardo

The move from the P45+ to the 160 for me was at first a tough call. I had spent 6 months getting my P45+ up to spec, (mine had the controller card that would not go to 1 hour, BTW a little known about issue). If you are looking for a use p45+ make sure you test it as I am sure there are more out there like mine. Since all warranties are off of the used backs now, it will be harder to get Phase to correct the problem.

For me, it's just the opposite. I used the P45+ for almost 4 years, used it hard. I quickly learned, expose for the highlights, and make sure you don't blow one as it's gone. Thus even at ISO 50, working with the P45+ was a mulit-shot show, most times 3. File size was not that big a deal so that was the way I went at it. I also noticed a big improvement in the 400 and 800 iso after Phase returned my back (new controller card that allowed me to run the most current firmware). But I still saw and still see when I work old files, what I call muddy blacks, and digital weirdness in the shadows. It's like the back was not able to figure out what to record in these parts of the image. Still when the exposure was good the results were top notch.

After a few demo's with Capture Integration with the P65+, I decided to trade the P45+ and upgrade. I also had read Don Libby's and Jack's posts on the P65+ and these helped a lot. Net, the DR of the P65+/160 is a huge step up from the P45+. It's there in the Dxomark scores, but I didn't really know how big it would be. You have so much more room between the shadows and highlights and now I often find it's just like a D800 file. Shoot for the middle you can recover a good bit of the highlights and the details in the shadows are just amazing. At first I wished I had done the P65+ a year earlier, but since I knew I also wanted a tech camera, I waited for the 160. Previous comments on the 2" LCD screen of the P45+ and P65+ are very true. It's a worthless screen and more times than not, when the screen showed me in focus, I would be out.

At first I missed the 1 hour reach. But in reality, for me, it was not that big a loss. Mainly since I shoot at night with the moon and thus I need to be able to stack, not leave the camera open for 1 hour, but instead take a long series of exposures and then combine them. You just get getter results this way. Here you can't use the P45+ as you end up with the dark frame each time, which ruins the sequence. Also in reality, if you are shooting say a 40min shot, it's pretty much one battery one shot as you still have to have enough battery to take the corresponding Dark frame. If your battery expired then the whole shot is gone.

As stated before the P45+ was a benchmark and a breakthrough. Phase was able to break new ground here. But after working with the newer Dalsa chips I am more than pleased to lose my 1 hour ability. Canon and Nikon fill that void very well.

Now with the reach of the D800, I have taken mine to 45 minutes just to see what I got, the 1 hour time of the P45+ is less important. Plus many are using the P645 Pentax at times of 1 hour or more and getting very good results. Not sure what Pentax is doing to allow longer times/less noise as I have never shot the P645, however I have worked with a few night shooters who have and their results were very impressive. From my understanding, the Pentax and P45+ ue the same Kodak chip.

Paul

 

[yaya]

Eduardo if you can find the serial number of the back you intend to buy then Phase One will be able to tell you the history and what kind of hardware revisions it's got in it. Easiest way to do that is via a certified dealer as they have direct contact with the service dept.

 

[dougpeterson]

Eduardo if you can find the serial number of the back you intend to buy then Phase One will be able to tell you the history and what kind of hardware revisions it's got in it.

Or of course you could purchase from a reputable dealer by which means you could avoid all the potential snags of scratched filters, dead ports, bad focus alignment, banged up chassis, missing accessories, "lemons". They would then also be there for you through all of your questions, issues, concerns. You can even get a warranty if it suits your needs/budget. (obvious self interest disclosed here).

 

[ondebanks]

But I have shot P25/45 non plus and P25 non plus is limited for the most part to about 40 seconds, while the P45 can go for at least several minutes. Don't know why this is,

Steve, I do know why this is. :toocool:

It's there in the Kodak datasheets for the KAF-22000 and KAF-39000.

You need one formula and four datasheet numbers to calculate the dark current at any temperature:
1) Dark-Doubling Temperature in ºC
2) Dark Reference Temp in ºC
3) Dark current at the Reference Temperature, in either mV/pix/s or pA/cm^2 [Kodak tend to use the former unit, Dalsa the latter]
4) One other parameter to convert mV/pix/s -> electrons/pix/s, or pA/cm^2 -> electrons/pix/s: either Gain in uV/electron for the former, or pixel size for the latter.

I've spreadsheeted-up all the MFD sensors I could get datasheets for.
(This might be an apt time to remind you that you more or less promised to source the IQ/Credo Dalsa CCD datasheets for me...hope I'm not :deadhorse

What this shows is that the KAF-39000 has 8.3x lower dark current than the KAF-22000 - at all temperatures. (This is because they have the same dark-doubling temperature. When comparing sensors with different dark-doubling temperatures, the dark current ratios vary with temperature).

That factor of 8 corresponds nicely to what you observed - 40 seconds vs. several minutes. Ta-da!

Ah, but if only the dark current behaviour of the Plus backs were as explicable as the non-Plus ones. Read on...

but it might explain the bias for P45+ and long exposure compared to those other models. It does indicate the possibility that the P45+ would provide a cleaner long exposure than the other Plus backs, given that the P45 non plus also did.

The 8x lower dark current does indeed explain an advantage of the P45+ over (most of) the other Plus backs with Kodak sensors. The other 9-micron backs (P20+, P21+) have similar dark currents to the P25+. But three questions arise:

1) If the P45+ shoots cleanly for an hour, then the datasheet-based calculation says that the P20+, P21+ and P25+ should only match it for an 8.3x shorter exposure - 7 minutes in round numbers. But I gather that in reality they do much better than that. WHY?

This goes to the next question:

2) How exactly does Xpose+ work?? What's it doing in terms of limiting dark current? Does it actively keep the sensors cool? (But since they have the same dark-doubling temperatures, cooling wouldn't change the 8x ratio...so that can't be it). Does it run the CCDs in a mode which departs from the data-sheet dark current rate? Does it switch off some components (amps etc.) which are not needed mid-exposure, only at the readout stage?

3) Since the P45+ and P30+ have sensors with the SAME dark current parameters (to within a fixed and pretty negligible 10% difference), why doesn't the P30+ have the same reputation for long exposures as the P45+?

There's a lot of PhaseOne expertise on this board, so I'm expecting some answers to these questions!

Ray

 

[GrahamWelland]

Ray,

Good info. I'd also like to know the real answers to some of your questions.

I know that before I bought my original P25+ I had my dealer run long exposure tests for me at room temperature in basically a dark room (lit only by light sneaking under the door). At ISO 50 the P25+ was still very very clean at 15 minutes which was good enough for my needs. I never really ran mine for longer than that although the Phase One specs suggested similar performance for all of the XPose+ backs but I've never seen a published test to back it up, just the satisfied anecdotal feedback from P45+ owners.

When I get my new P25+ in the next couple of weeks I'll perhaps have to run some tests and share them (although without the benefit of a P45+ to test against).

 

[Audii-Dudii]

3) Since the P45+ and P30+ have sensors with the SAME dark current parameters (to within a fixed and pretty negligible 10% difference), why doesn't the P30+ have the same reputation for long exposures as the P45+?

As it happens, I own a P30+ and do a lot of night photography. For a few weeks, I also owned a P45+, but ultimately decided it wasn't worth the additional expense relative to my P30+ (which I bought used for an almost too-good-to-be-true price) and when I received an offer I couldn't refuse, I sold it.

In my (admittedly limited) experience, the two performed pretty much equally in terms of their long-exposure ability, so long as the P45+ was used at ISO100. When it was used at ISO50, then it was indeed capable of longer exposures. Of course, longer exposures were also necessary to gather the same amount of light, so I didn't find this to be a significant advantage, as I didn't find the image quality (for my night photography, at least) to be noticeably better at ISO50 than it was at ISO100.

I think a lot of people overlook this distinction and that's one of the reasons why the P45+ has the reputation it does. Of course, it also offers many other advantages, such as the larger sensor, lack of microlenses, etc., but apples-to-apples, I didn't find it to perform any better with the type of long exposures I typically do with my P30+ (i.e., 2-10 minutes). YMMV, of course...

P.S.: The P30+ also has a reputation for not being usable with movements, but I have found this isn't strictly true. If you're using lenses with a long register -- such as the modified Mamiya 50mm/F4 PC lens that I use on my Contax 645 body -- you can get away with some amount of shift before vignetting sets in ... say, 8-10mm. This may not sound like a lot, but it's 20% of the frame length and is generally sufficient for my purposes. Beyond there, though, lie dragons and by 12mm, the outer edges of the frame start to turn black ... not just dark, but black. As such, it won't work with a technical camera, but to say it can't be used with movements, period, is perhaps a little bit misleading...

 

[Zerimar]

P45+ definitely is the king of long exposures, as shown by this 1 hour 26 minute exposure.
1 hour 26 minutes, Peaks. by RickrPhoto, on Flickr

I am going to attempt a 3 hour one this evening to see my results.

 

[Uaiomex]

Thank you Rick. You are a great P45+ ambassador.
Eduardo