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Thread: Phase One P45+ Life

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    Senior Member Albino_BlacMan's Avatar
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    Phase One P45+ Life

    What's the expected life (shutter actuation wise) for a Phase One P45+.

    Also what is the best way to check shutter actuations?

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    Re: Phase One P45+ Life

    The P45+ as a digital back, like all Phase One backs have very little in the way of mechanical things that could go wrong; there the locking to the body, the card door and release. The rest as far as I know are all electrical. That said, there's little from my understanding to actually wear out. But crap happens.

    As far as telling how many image files have been captured you need to turn the back on and go to the menu. Look for the screen that shows the firmware and you'll see how many files have been processed.

    Hope that helps.

    Don
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    Senior Member Albino_BlacMan's Avatar
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    Re: Phase One P45+ Life

    So I guess my question is when would one start being concerned that the back is wearing out? I know 50k is barely breaking in a DSLR but my understanding is that MF backs aren't made for that kind of use? Or is that incorrect?

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    Senior Member kdphotography's Avatar
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    Re: Phase One P45+ Life

    I think you've got it backwards. The medium format camera and its lenses are more similar to the DSLR in that they are subject to wear and tear with use. A MFDB has very few moving parts. I recall reading that the Phase One MFDBs or sensors are engineered more towards a million captures. No one will ever know, because here in Dante's Forum it's always customary to trade in our MFDBs and upgrade as soon as our wallets have recovered from the first time round.

    Of course those same old MFDBs are still working, and you'd be surprised how many MFDBs are simply moving around back and forth exchanging ownership amongst the GetDPI family.

    I'd place my money on a MFDB far outlasting any DSLR in use. Wear and tear on a medium format camera body is a different story.

    ken

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    Super Duper
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    Re: Phase One P45+ Life

    Two totally separate things, a (any) DSLR vs. a (any) digital back. The camera body's weakest part is the shutter. There's also all types of mechanical things going on every time the shutter button is pressed. No so with a digital back where electrons are working to save the file (very simplistic point of view). Bottom line as far as I know and understand it a camera body will wear out much sooner than a digital back.

    That said, if buying a used back it would be best to have it first checked out with a trusted dealer to insure everything is okay.

    I'm now on my 4th digital back, and no none of them ever wore out. My first one was a P30+ I bought new then later traded/upgraded to a used P45+ which was later traded/upgraded to a used P65+ which was later traded/upgraded to a used IQ160. My current back will soon be traded/upgraded again to a used IQ180. While things certainly can go wrong the one thing I've never been concerned with is my digital back wearing out.
    Don Libby
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    Re: Phase One P45+ Life

    Ken responded will I was typing. I remember reading the same 1 million figure but didn't want to share it as I thought I had mis-remembered the figure.

    You've now heard from 2-photographers. Hopefully Doug or Steve or someone how actually sells and has a company that offers customer service will chime in.

    I was once invited to visit Phase One but I didn't go because I was told I'd be escorted the entire time by armed people and that I had to keep my hands in my pockets and a body search was to be made at the end. Took all the fun out of it.

    All kidding aside digital backs (at least Phase One from personal experience) are like the engerizer bunny. They just keep going...

    Don
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    Re: Phase One P45+ Life

    I have owned many digital backs (Leaf DDB I then II, Phase One H5, H10, H25, P25, P45+,P40+, P65+, Leaf Aptus 12, Phase One IQ180). I also spent 7 years as a senior manager in an organisation in Australia that owned and operated more than 30 backs in studios across the country that were deployed in shooting most of the retail catalogues for the big retailers in Australia. These backs were shooting hundreds of frames each day, in the case of some clients by multiple shifts working 2 and occasionally 3 eight -hour shifts a day. In the last ten years, my personal backs have been dragged through Arabian deserts in high summer, SE Asian jungles during the monsoon and high in the snow country in the Swiss Alps. What I can say is that I have NEVER seen a back become unreliable due to overuse. Mechanical parts sometimes fail. These include memory card doors, a couple of Leaf cooling fans (a miracle considering summer temps in Oz and the backs almost continual use) and once, a mount lock. All other repairs we had were due to being dropped or carelessness causing scratches to sensor protectors. The electronics/sensors seem to be pretty much bulletproof.
    If your question relates to a potential purchase of a used P45+, the the primary concern I would have would be to satisfy myself that the back has not been physically abused. Usually, if a back has been banged and bashed around, the case will tell you pretty clearly. The P series cases are tough as nails (my P25+ was dropped on concrete floors and on rocks more times than I care to admit, though happily, none of my subsequent backs have bounced). The black paint can show some wear on corners and sharp corners but this is not so worrisome. On the other hand if there were any dings in metalwork, or gauges in paintwork that was clearly not ordinary wear on exposed edges, then I'd treat the back as if it had ebola.
    Bottom line is, in my view, unless the back has a huge amount of exposures on it (for me, that grey area approaches in the 300-400k exposure zone, but you have to form your own view. My view is based on my own observations), I would consider buying it if it appears in good physical condition. A few test shots in various conditions should reveal any calibration issues, though these should have been mostly identified by first owners and sorted under warranty.
    Best of luck.
    Siebel
    "In the end, it's all about the pictures"
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    Senior Member Albino_BlacMan's Avatar
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    Re: Phase One P45+ Life

    Thanks for all the great advice!

    The next question is how much is a P45+ in V mount worth?

    Chris

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    Re: Phase One P45+ Life

    seen from an technical standpoint, way less than any camera with the 36mp sony sensor.
    - better dynamic range
    - better iso performance
    - better, smaller, more universal bodys
    - can be lighter and more compact than any MF system

    but there are reasons to buy such an digi back of course, for some people.
    - updating an existing system
    - they believe in the cmos color, or look, what ever that means... voodoo imo
    - same as the above, but replace the cmos with lenses... voodoo imo

    if you want an nice P45+, be prepared to pay about 4-5 times as much as an A7R goes for.
    Last edited by mbn; 31st October 2014 at 09:23.

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    Senior Member kdphotography's Avatar
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    Re: Phase One P45+ Life

    Shoot the Sony A7r and a MFDB system side by side, especially a nice compact technical camera.

    Keep what gives you the most kicks, grins, and giggles.

    Better yet, get both. I didn't like the A7r---felt like a fancy P&S. It sings as an IR camera though!

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    Re: Phase One P45+ Life

    I'm currently using an IQ160 on both a DF and WRS and also have a Sony A7r converted to shoot full spectrum. To me and what I want and am looking for; the IQ beats the image files from the 7r. I have always preferred the files from any medium format back to any 35mm (and I've shot with the Ds, Ds II and Ds III) the nearest I've come was when I also shot with a Leica M9 while still using a P45+. But you use the tool that fits the location and hope for the best.

    I'll be going to Moab and the South Rim in December and will in all likelihood take everything with me. If the conditions are perfect I have a hike planned that will require several hours and a lot of elevation change and since I'm getting lazy I plan on taking the 7r. I also have a few spots in mind that require just a little effort and will take the WRS. I also have another location where I'll in all likelihood take the DF. In the end I also have a close to 15 mile hike that I haven't been on before and since I'm uncertain what I'll be running into plan on going light in camera gear so I can take more water and plan to taking the 7r with a new (I should get it by then) 16-35.

    In a perfect word where I had someone carrying my gear for me I'd never take anything other than medium format. In other words let the situation detect the equipment; not what other people feel is best.

    don
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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: Phase One P45+ Life

    I'd worry less about actuations and more about flight time in aeroplanes. Cosmic rays and other high energy particles will gradually kill off pixels etc over enough time. Seriously.
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

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    Re: Phase One P45+ Life

    Quote Originally Posted by GrahamWelland View Post
    I'd worry less about actuations and more about flight time in aeroplanes. Cosmic rays and other high energy particles will gradually kill off pixels etc over enough time. Seriously.
    Really?!!! How much is "over enough time" and where has this info come from? My IQ180 has hundreds of hours logged with no sign of any shift whatsoever. There are also lots of backs doing massive amounts of airtime on military and civvy aerial photography platforms. I would have thought we'd have heard about this before.
    If it wasn't for the use of the word seriously I'd have thought you were trolling, but that's not a game I've ever seen you play Graham.
    Siebel
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    Re: Phase One P45+ Life

    I know it sounds fanciful but air travel and exposure to high energy particles such as gamma rays fries lcd, ccd, and memory chips over time. No, I'm not making this up. It's a cause for dropped pixels and memory bits.

    Now should you wrap your camera in lead? No, don't bother.
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

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    Senior Member ondebanks's Avatar
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    Re: Phase One P45+ Life

    Quote Originally Posted by siebel View Post
    Really?!!! How much is "over enough time" and where has this info come from? My IQ180 has hundreds of hours logged with no sign of any shift whatsoever. There are also lots of backs doing massive amounts of airtime on military and civvy aerial photography platforms. I would have thought we'd have heard about this before.
    If it wasn't for the use of the word seriously I'd have thought you were trolling, but that's not a game I've ever seen you play Graham.
    No, Graham is correct that environmental radiation damage occurs to sensors and their associated electronics. The main impact is in elevated dark ("thermal") noise, which may be very noticeable at individual pixels - this is why there is a slow but inexorable rise in "hot" pixels over time, that have to be re-mapped out.

    But perhaps he is overstating its severity - consider that cameras on the Hubble Space Telescope have operated for up to a dozen years each before replacement, and that is in the much harsher radiation environment of space. I've worked with HST exposures that are so peppered with cosmic ray hits that it's hard to distinguish any of the real stars. This is one reason why very long exposures are subdivided into multiple shorter ones, and stacked with aggressive statistical thresholding.

    Ray
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    Re: Phase One P45+ Life

    Quote Originally Posted by GrahamWelland View Post
    Now should you wrap your camera in lead? No, don't bother.
    What about tin foil?
    Peter
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    Re: Phase One P45+ Life

    Quote Originally Posted by GrahamWelland View Post
    I know it sounds fanciful but air travel and exposure to high energy particles such as gamma rays fries lcd, ccd, and memory chips over time. No, I'm not making this up. It's a cause for dropped pixels and memory bits.

    Now should you wrap your camera in lead? No, don't bother.
    Well there ya go! Learnt something new today!
    Siebel
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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: Phase One P45+ Life

    Perhaps I should clarify my original post. I wouldn't be worried about the electrical effects of running a back with lots of actuations. I was actually being somewhat ironic about worrying more about cosmic rays as what I'd care about with a used back.

    I do agree however that a high shot count probably is associated with more physical wear and tear such as sensor cleans, mount/unmount on camera bodies, button wear plus any associated wear on the connectors if it's been used for tethered shooting with cables being shoved in & out of the various orifices on the back.

    The reality of sensor exposure to high altitude conditions is just that more pixels will end up being mapped out. You might even get dark/stuck pixels on the LCD too over time. Is it a serious reason to panic? Not in the slightest unless you're up in the space station.

    I fly 150k+ miles a year and so I'm somewhat conscious of the health impacts of sitting in an aluminum tube at 36,000 ft for hours on end (8hrs today for example). That includes being irradiated, although not as much as being stuck around other people, jet lag, DVT risk, being turned into a raging alcoholic in first class etc.
    Last edited by GrahamWelland; 1st November 2014 at 23:48.
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

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    Senior Member kdphotography's Avatar
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    Re: Phase One P45+ Life

    Quote Originally Posted by Pemihan View Post
    What about tin foil?
    Absolutely, Peter!

    Foil is the perfect protection for your head and stops all the voices too...


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    Re: Phase One P45+ Life

    But those voices are telling me to buy more equipment!

    Don Libby
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    Re: Phase One P45+ Life

    Quote Originally Posted by Don Libby View Post
    But those voices are telling me to buy more equipment!

    Then for Gods sake throw the tin foil in the trash and listen to the voices and repeat after me: buy more equipment, buy more equipment. buy more equipment...
    Peter
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    Re: Phase One P45+ Life

    I must obey...
    Don Libby
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    Senior Member ErikKaffehr's Avatar
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    Re: Phase One P45+ Life

    Ray,

    HST, that sounds like a really nice telephoto lens!

    Best regards
    Erik


    Quote Originally Posted by ondebanks View Post
    I've worked with HST exposures that are so peppered with cosmic ray hits that it's hard to distinguish any of the real stars. This is one reason why very long exposures are subdivided into multiple shorter ones, and stacked with aggressive statistical thresholding.

    Ray

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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: Phase One P45+ Life

    Quote Originally Posted by siebel View Post
    Well there ya go! Learnt something new today!
    Any day that I learn something new is a good day in my book.
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"
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    Senior Member ondebanks's Avatar
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    Re: Phase One P45+ Life

    Quote Originally Posted by ErikKaffehr View Post
    Ray,

    HST, that sounds like a really nice telephoto lens!

    Best regards
    Erik
    HI Erik,

    Yes, it's amazing what you can do with a 57600 mm focal length telephoto!

    Here's something I made with it many years ago...supernova remnant CTB80, an RGB tricolour composite with R = ionised Sulphur, G = ionised Hydrogen, and B = Stromgren y continuum band. The white circle marks the location of a radio pulsar that we were trying to locate in visible light.



    I get a kick out of the fact that the Hubble has a native focal ratio of f/24, and many of its instrument modes increase that number, to as high as f/288. You can already picture a few photography "gurus" throwing up their hands in horror - "You mustn't shoot at such small f-stops - you'll get terrible diffraction softness!" - or even better - "Of course, the reason they use such slow f-ratios is to increase the depth of field"

    Ray

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    Re: Phase One P45+ Life

    I think the diffraction police just died.
    My little corner on the internet.
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    Re: Phase One P45+ Life

    Quote Originally Posted by ondebanks View Post
    HI Erik,

    Yes, it's amazing what you can do with a 57600 mm focal length telephoto!

    Here's something I made with it many years ago...supernova remnant CTB80, an RGB tricolour composite with R = ionised Sulphur, G = ionised Hydrogen, and B = Stromgren y continuum band. The white circle marks the location of a radio pulsar that we were trying to locate in visible light.



    I get a kick out of the fact that the Hubble has a native focal ratio of f/24, and many of its instrument modes increase that number, to as high as f/288. You can already picture a few photography "gurus" throwing up their hands in horror - "You mustn't shoot at such small f-stops - you'll get terrible diffraction softness!" - or even better - "Of course, the reason they use such slow f-ratios is to increase the depth of field"

    Ray
    Is it not diffraction that is clearly visible in that shot though? After all, every single one of those stars is a point source of light, no?

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    Re: Phase One P45+ Life

    Quote Originally Posted by gerald.d View Post
    Is it not diffraction that is clearly visible in that shot though? After all, every single one of those stars is a point source of light, no?
    Yes, indeed. Every star is a point source, so every star imaged through an optical system is itself a point-spread function (PSF). The x-shaped spikes you see through the stars are caused by diffraction at the support vanes for the secondary mirror. And although not visible at this scale, the core of each star image (PSF) is essentially an Airy diffraction pattern, the holy grail of any optical design.

    My point is that
    (1) being diffraction limited is good - it cannot be improved upon; and
    (2) what's more important than obsessing about a specific f/stop number is what your sampling of the PSF is. With chunky pixels, it's entirely appropriate to use f/[big number].

    Ray

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    Re: Phase One P45+ Life

    Quote Originally Posted by ondebanks View Post
    Yes, indeed. Every star is a point source, so every star imaged through an optical system is itself a point-spread function (PSF). The x-shaped spikes you see through the stars are caused by diffraction at the support vanes for the secondary mirror. And although not visible at this scale, the core of each star image (PSF) is essentially an Airy diffraction pattern, the holy grail of any optical design.

    My point is that
    (1) being diffraction limited is good - it cannot be improved upon; and
    (2) what's more important than obsessing about a specific f/stop number is what your sampling of the PSF is. With chunky pixels, it's entirely appropriate to use f/[big number].

    Ray
    Ok, you've lost me a bit here on the context of the discussion (not on the context of the science - I have a physics degree.)

    You seemed to be inferring earlier with your sarcastic "mustn't shoot at such small f-stops" comment that those who consider such things are somehow missing the bigger picture.

    Regardless of "chunky pixels", there is no arguing whatsoever about the simple fact that because that image you are sharing was shot at such a small aperture, you are losing a huge quantity of information because of diffraction problems.

    I'm not referring to the cross here - I'm referring to the fact that you have point sources of light that, due to diffraction issues that are exacerbated by the size of the chosen aperture, are masking data in the image.

    Look at any of the "bright" stars in that image. Due to diffraction, they are destroying data that would (theoretically) otherwise be available.

    Isn't that the reason why photography "gurus" take diffraction into consideration?

    Kind regards,


    Gerald.

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    Senior Member ErikKaffehr's Avatar
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    Re: Phase One P45+ Life

    Hi,

    The case is that NASA is not stopping down, they use a barlow lens (tele extender) to increase the focal length. So f-stop is going down as it is diameter of the mirror divided the focal length.

    To achieve a good spatial resolution on large pixels they need to have a large image. The angular resolution of the telescope is limited by the diameter of the lens (mirror), but an extended focal length is needed to utilise that angular resolution with fat pixel sensors. I guess that those pixels are large (200 microns?)

    Now, why do they have that large pixels? Well my guess is that they try to catch photons from far away which are not very abundant. Increasing the area of a pixel increases the probability of detection.

    Now let's assume that pixel size is something like 200 micron. That is 29 times the size of a P45+ pixel, but area would be 29x29 = 841 times larger. So if a p45+ pixel would collect 10 photons the 200 micron sensor would yield 8410 counts. Now, the P45+ has a readout noise of about 10 electron charge, so SNR would be 1, that is a barely usable signal. The sensor on Hubble may have much lower readout noise as it is in a very cold environment like 78K.

    Best regards
    Erik


    Quote Originally Posted by gerald.d View Post
    Ok, you've lost me a bit here on the context of the discussion (not on the context of the science - I have a physics degree.)

    You seemed to be inferring earlier with your sarcastic "mustn't shoot at such small f-stops" comment that those who consider such things are somehow missing the bigger picture.

    Regardless of "chunky pixels", there is no arguing whatsoever about the simple fact that because that image you are sharing was shot at such a small aperture, you are losing a huge quantity of information because of diffraction problems.

    I'm not referring to the cross here - I'm referring to the fact that you have point sources of light that, due to diffraction issues that are exacerbated by the size of the chosen aperture, are masking data in the image.

    Look at any of the "bright" stars in that image. Due to diffraction, they are destroying data that would (theoretically) otherwise be available.

    Isn't that the reason why photography "gurus" take diffraction into consideration?

    Kind regards,


    Gerald.
    Last edited by ErikKaffehr; 5th November 2014 at 13:24.

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    Re: Phase One P45+ Life

    Quote Originally Posted by gerald.d View Post
    Ok, you've lost me a bit here on the context of the discussion (not on the context of the science - I have a physics degree.)
    Sure, we're way OT, but we got here by the usual organic thread drift:
    - OP asked about P45+ lifetime
    - Graham commented on lifetime effects of sensor and LCD aging by radiation exposure
    - I agreed with Graham, but added that HST sensors last well despite intense radiation bombardment
    - Erik commented that HST must be a great long telephoto
    - I agreed, and showed an example from my own HST work...which reminded me of a time when someone who should have known better criticized NASA for using such large f/numbers, on the basis of the spectre of diffraction.
    - and so here we are, talking about space telescope point-spread functions and diffraction, when we should be talking about the lifetime of a particular digital back.

    Quote Originally Posted by gerald.d View Post
    You seemed to be inferring earlier with your sarcastic "mustn't shoot at such small f-stops" comment that those who consider such things are somehow missing the bigger picture.
    No, I was just joking about the tendency among some "experts" to decry anything slower than about f/16 as a no-go area because of diffraction - Synn put it well, "the diffraction police". As I said, I was involved in a discussion, long time ago, where the HST's large f-numbers needlessly raised eyebrows. They weren't missing the bigger picture - they were missing the context that detail, angular resolution, is determined by physical aperture and not by focal ratio, and that there are two ways to arrive at a slower focal ratio: take a fast lens and stop it down; or take a fast lens and optically amplify its focal length. The first way decreases the resolution that the system is capable of, and that's the only way they were thinking of; but the second way preserves the angular resolution (and the photon collecting area), and that's what happens with telescopes.

    Quote Originally Posted by gerald.d View Post
    Regardless of "chunky pixels", there is no arguing whatsoever about the simple fact that because that image you are sharing was shot at such a small aperture, you are losing a huge quantity of information because of diffraction problems.
    When you say "that image you are sharing was shot at such a small aperture", you are falling into the same misconception as the folks I was describing above - thinking with the photographer part of your brain rather than the physicist part. It wasn't shot at a small aperture - not unless you regard 2.4 metres as small. It was shot at a slow f/ratio, but that's a different thing. They could have designed the HST as a much faster optical system, while maintaining the 2.4m entrance pupil aperture constraint...it would resolve neither more nor less detail; it would just require smaller pixels to maintain reasonable PSF sampling, and smaller pixels would be quicker to saturate and generally have proportionally higher readout noise. So, they made it slow, and used large-pixel (15 micron) CCDs.

    Quote Originally Posted by gerald.d View Post
    I'm not referring to the cross here - I'm referring to the fact that you have point sources of light that, due to diffraction issues that are exacerbated by the size of the chosen aperture, are masking data in the image.

    Look at any of the "bright" stars in that image. Due to diffraction, they are destroying data that would (theoretically) otherwise be available.
    You are absolutely correct that there is theoretically more data/resolution to be had. But it would take a larger diameter telescope to obtain it - and if you were to say, increase the aperture 2x, then the optical surface areas to be meticulously figured increase 4x, the mass and volume increase 8x, the launcher capacity and payload requirements increase by a similar amount, the construction and testing budgets increase probably 10x, and everything takes longer, so launch is delayed by years...and then at the end of it all, you find that even when you jump up and down on it, it doesn't fit in the Space Shuttle's payload bay This makes the phrase "exacerbated by the size of the chosen aperture" inappropriate in this context - it implies that there was an easy choice available to use a larger aperture.

    Quote Originally Posted by gerald.d View Post
    Isn't that the reason why photography "gurus" take diffraction into consideration?
    It is the reason, but I hope I've shown why it's wrong to apply photographic diffraction considerations to all imaging contexts.

    Cheers,
    Ray

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    Re: Phase One P45+ Life

    Quote Originally Posted by ErikKaffehr View Post
    Hi,

    The case is that NASA is not stopping down, they use a barlow lens (tele extender) to increase the focal length. So f-stop is going down as it is diameter of the mirror divided the focal length.

    To achieve a good spatial resolution on large pixels they need to have a large image. The angular resolution of the telescope is limited by the diameter of the lens (mirror), but an extended focal length is needed to utilise that angular resolution with fat pixel sensors. I guess that those pixels are large (200 microns?)

    Now, why do they have that large pixels? Well my guess is that they try to catch photons from far away which are not very abundant. Increasing the area of a pixel increases the probability of detection.

    Now let's assume that pixel size is something like 200 micron. That is 29 times the size of a P45+ pixel, but area would be 29x29 = 841 times larger. So if a p45+ pixel would collect 10 photons the 200 micron sensor would yield 8410 counts. Now, the P45+ has a readout noise of about 10 electron charge, so SNR would be 1, that is a barely usable signal. The sensor on Hubble may have much lower readout noise as it is in a very cold environment like 78K.

    Best regards
    Erik
    Thanks for chipping in, Erik. You are correct on most points. The pixel size is not as big as you thought, and the primary factor deciding pixel size is the PSF sampling rather than flux collection probability (after all, if an incoming photon misses one small pixel, it will hit the one beside it). But you are right that readout noise is lower than in MFD CCDs (5 electrons/pixel for the original workhorse WFPC2 camera, which is impressive for something made in the early 1990s).

    Cheers,
    Ray

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    Senior Member ErikKaffehr's Avatar
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    Re: Phase One P45+ Life

    Hi,


    What is the pixel size?

    I was also a bit surprised to read that original sensor have been cooled by nitrogen, as it is quite cold out there. But than I realised that with near vacuum conditions there would not be any cooling by convection.

    Nice picture, by the way! Surprised to see it in colour, though!

    Best regards
    Erik


    Quote Originally Posted by ondebanks View Post
    Thanks for chipping in, Erik. You are correct on most points. The pixel size is not as big as you thought, and the primary factor deciding pixel size is the PSF sampling rather than flux collection probability (after all, if an incoming photon misses one small pixel, it will hit the one beside it). But you are right that readout noise is lower than in MFD CCDs (5 electrons/pixel for the original workhorse WFPC2 camera, which is impressive for something made in the early 1990s).

    Cheers,
    Ray

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    Re: Phase One P45+ Life

    Quote Originally Posted by ErikKaffehr View Post
    Hi,

    What is the pixel size?
    The pixel size is 15 microns for that camera.

    Quote Originally Posted by ErikKaffehr View Post
    I was also a bit surprised to read that original sensor have been cooled by nitrogen, as it is quite cold out there. But than I realised that with near vacuum conditions there would not be any cooling by convection.
    Forced cooling of the CCDs is still necessary in space, because HST spends half of each orbit in the full glare of unfiltered sunlight. Internal conduction and radiation would transmit some of the absorbed heat to the sensors.

    And even if the average sensor temperature was still very, very cold, any uncontrolled rise and fall in temperature, however small, is undesirable from the point of view of maintaining a stable instrument calibration during science programmes. In other words, just cooling isn't enough - it must be regulated cooling to a set point of temperature. So the WFPC2 was maintained at -88 Celcius.

    The visible light cameras (like the WFPC2, ACS, and WFC3) actually don't use cryogenic coolants like nitrogen or helium - they use thermoelectric coolers instead. This gives them an essentially unlimited lifetime. OTOH, infrared cameras (like the NICMOS) require deeper cooling - otherwise the camera detects its own thermal infrared signature as an interfering background! - and that means cryogenics. However, the Helium boils off over time, which sets a limit to the useable lifetime of the camera - unless a servicing mission flies in to replace the dewar.


    Quote Originally Posted by ErikKaffehr View Post
    Nice picture, by the way! Surprised to see it in colour, though!

    Best regards
    Erik
    Thanks! It's in colour because I made a tricolour composite of grey images through 3 different filters. An old technique that dates back to James Clerk Maxwell in 1861.

    (And BTW, Ctein's rant about this, while interesting, misses the point: tricolour techniques are not at all confined to literally use red, green and blue filtration - any three spectral bandpasses can be used, from gamma rays down to radio waves).

    Cheers,
    Ray

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    Re: Phase One P45+ Life

    Quote Originally Posted by ondebanks View Post
    Sure, we're way OT, but we got here by the usual organic thread drift:

    <snip>

    Cheers,
    Ray
    Thanks

    Kind regards,

    Gerald.

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    Re: Phase One P45+ Life

    Quote Originally Posted by ondebanks View Post
    The pixel size is 15 microns for that camera.

    Forced cooling of the CCDs is still necessary in space, because HST spends half of each orbit in the full glare of unfiltered sunlight. Internal conduction and radiation would transmit some of the absorbed heat to the sensors.

    And even if the average sensor temperature was still very, very cold, any uncontrolled rise and fall in temperature, however small, is undesirable from the point of view of maintaining a stable instrument calibration during science programmes. In other words, just cooling isn't enough - it must be regulated cooling to a set point of temperature. So the WFPC2 was maintained at -88 Celcius.

    The visible light cameras (like the WFPC2, ACS, and WFC3) actually don't use cryogenic coolants like nitrogen or helium - they use thermoelectric coolers instead. This gives them an essentially unlimited lifetime. OTOH, infrared cameras (like the NICMOS) require deeper cooling - otherwise the camera detects its own thermal infrared signature as an interfering background! - and that means cryogenics. However, the Helium boils off over time, which sets a limit to the useable lifetime of the camera - unless a servicing mission flies in to replace the dewar.
    I read about nitrogen cooling on the web, nice to have up to date info. Temperatures in near vacuum conditions is a quite interesting subject. :-)

    Nice to hear about "unlimited lifetime". I guess that the HST is one of the most valuable resources to astronomers.


    Thanks! It's in colour because I made a tricolour composite of grey images through 3 different filters. An old technique that dates back to James Clerk Maxwell in 1861.
    Well, my thinking was more like that HST time is pretty scarce, I guess. NASA publishes some images for sheer beauty, but I guess that many observations are monochrome. So I guess that if nice multispectral images needs to be shot, there needs to be a scientific need for that.


    BTW, It could be nice if you would elaborate a bit more on the PSF/diffraction and pixel size issue.

    Best regards
    Erik
    Last edited by ErikKaffehr; 6th November 2014 at 10:37.

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