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Author Topic: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know  (Read 106988 times)

torger

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #140 on: March 11, 2013, 10:27:55 am »

In my experience the difficulty of ground glass focusing is more-than-expected difficult as you step up in resolution. Ground glass focusing a 22mp back vs. an 80mp back is a very different experience.

I also agree aperture matters: a Roddy f/4 lens is a good bit easier to focus than a Schneider f/5.6 lens.

The hardest part is to focus on a flat surface with a largish shooting aperture, say a painting on a wall at f/8 or even f/5.6. Then focusing errors is noted the most. At f/11 for 3D subjects it becomes drastically easier, simply because it is less visible exactly where the focus plane sits. It still is some element of skill to it though, one has to concentrate to make the best out of it and one gets better with training.

If one needs absolute safety one cannot beat high precision focusing rings with laser distance metering though. For indoor architecture the poor light + flat surface challenge arises often enough to make pancake camera with HPF desirable, but for landscape I would not have any trouble to do 80 megapixels with my Techno (Joe Cornish is one example of a pro photographer that actually does it).
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BJL

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resolution limits of the secondary image scattered off the ground glass
« Reply #141 on: March 11, 2013, 10:57:00 am »

The ground glass has got more bashing on this forum than it deserves. All it takes is a strong loupe and some confidence ;).
A loupe does not completely overcome the fact that the secondary image that one sees scattered off the ground glass has distinctly less resolution than lenses delivers or sensors can record. From what I have read, the image coming from the "ground glass" (frosted plastic?) of a 35mm format SLR has resolution comparable to only about a 2MP sensor.  Presumably the OVF resolution is several times better for medium format, especially if the VF designs are still more oriented to manual focusing than modern 35mm format SLR viewfinders are, but I doubt than any OVF or view camera ground glass comes close to matching 60MP+ sensors.
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torger

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #142 on: March 11, 2013, 11:43:31 am »

A loupe does not completely overcome the fact that the secondary image that one sees scattered off the ground glass has distinctly less resolution than lenses delivers or sensors can record. From what I have read, the image coming from the "ground glass" (frosted plastic?) of a 35mm format SLR has resolution comparable to only about a 2MP sensor.  Presumably the OVF resolution is several times better for medium format, especially if the VF designs are still more oriented to manual focusing than modern 35mm format SLR viewfinders are, but I doubt than any OVF or view camera ground glass comes close to matching 60MP+ sensors.

I've actually measured this on my Techno, and visible detail on the ground glass under magnification corresponds to about what you would see in an ~18 megapixel image in the 48x36mm area. So how is this enough for an 80 megapixel sensor? Since you work with small shooting apertures the DoF/diffraction masks the exact position of the focus plane so the focusing errors you do is masked, and in many types of scenes the exact position is actually not that important.

If you would pixel peep 80 megapixel f/2.8 portrait images focused on the eyeball manual focus on the ground glass would be near hopeless of course, but the view camera application is generally not that. If you actually do need the best precision in focus plane placement for a technical camera then high precision focusing ring is the answer (assuming you don't tilt). For MFD SLRs there's phase-detect autofocus.

Shooting style shifts a bit depending on what the camera is good at. I use tilt a lot (which for many scenes makes focusing more forgiving by the way), many pancake camera users use focus stacking a lot but rarely tilt.

At some point it becomes a problem though. When you get very high resolution, say 200+ megapixels and don't want to kill detail with diffraction, image making for the type of landscape subjects I like to shoot becomes unpractical. I don't like focusing stacking, I want to capture it all in one shot. I think f/11 is a good shooting aperture for landscape and MFD, and for that ground glass can certainly be adequate. But if we would like to focus stack several f/5.6 images to make the final image the ground glass is indeed obsolete (live view is not good for that either, again the high precision focusing ring is the answer).
« Last Edit: March 11, 2013, 11:56:49 am by torger »
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FredBGG

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #143 on: March 11, 2013, 01:59:15 pm »

I've actually measured this on my Techno, and visible detail on the ground glass under magnification corresponds to about what you would see in an ~18 megapixel image in the 48x36mm area. So how is this enough for an 80 megapixel sensor? Since you work with small shooting apertures the DoF/diffraction masks the exact position of the focus plane so the focusing errors you do is masked, and in many types of scenes the exact position is actually not that important.

Are you claiming that a ground glass focusing screen can resolve  9 or 10 microns...... ?

I can see peach fuzz in an 11 MP photo and heave never been able to see peach fuzz through and ground glass screen even with a Leica or Fuji loup.
Even on an 4x5 or 8x10 shooting with HMIs even with special focusing screens. Accute Matte or whatever. Not to mention that with a loup anywhere away from
the very center of the lens becomes way less clear unless using a very long lens.
« Last Edit: March 11, 2013, 02:05:42 pm by FredBGG »
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FredBGG

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #144 on: March 11, 2013, 02:23:29 pm »

At some point it becomes a problem though. When you get very high resolution, say 200+ megapixels and don't want to kill detail with diffraction, image making for the type of landscape subjects I like to shoot becomes unpractical. I don't like focusing stacking, I want to capture it all in one shot. I think f/11 is a good shooting aperture for landscape and MFD, and for that ground glass can certainly be adequate. But if we would like to focus stack several f/5.6 images to make the final image the ground glass is indeed obsolete (live view is not good for that either, again the high precision focusing ring is the answer).

How can a ground glass be just fine for an 80MP sensor and no good for a 200MP sensor that is a multi shot from a 50 MP sensor. The 80MP sensor actually only
has 36.81 % less resolution than a 200 MP MS and that is only if the lens still out resolves the 200MP capture.

(percentage difference going from 16,352 to 10,328)

I really don't see how the ground glass could be just fine for 80PM and obsolete for a 200MP image.

Also when it comes to focus stacking you only have to select a range of focusing. After that nothing is better than
remote control of focusing. Even a precision focusing ring means you have to touch the camera. You would need one hell of a camera stand to avoid moving
the sensor at a micron level.
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Enda Cavanagh

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #145 on: March 11, 2013, 02:25:24 pm »

Bear in mind the base ISO of the long exposure is now ISO140 rather than ISO50 (as it was with the P45+). So if the P45+ required an hour for a given scene the IQ260 will only require 20 minutes, followed by a 20 minute dark frame - 20 minutes LESS than the hour the P45+ required just to do the capture (let along the dark frame).

Now if your goal is specifically to do time lapse or star trails, in which you only care about doing multiple exposures in a row with minimal gap (rather than getting enough light from a given scene for a good exposure) then the dark frame sucks. There are some work arounds for some situations; others it's a simple no-go.

Of the backs that don't require a dark frame the longest exposure specification is 256 seconds at ISO100. So for anyone who wants more than that in a digital back this is the best solution out there. You have to give them some credit for getting much more in the way of long exposure out of each sensor than anyone else has. If it doesn't work for your needs I totally understand, but that doesn't make it a "waste of time" for everyone; others will have other needs which this fits extremely well.

Now, why the dark frame can't be turned off for shorter exposures (e.g. 15 seconds) where it's conceivable that you could maybe get good quality without it - that does irk me a bit. I'll be speaking with R+D about the technology behind the IQ260 long exposure soon and will ask about this.

Hi Doug.
The argument that because the base exposure is greater doesn't do it for me I'm afraid. If I had to wait 1 hr I'd be pissed off. If I had to wait 20 minutes I'd be pissed off. If I had to wait 256 seconds I'd be pissed off.  :) For a lot of people who earn from photography it would be a waste of time. Grand if you are a hobbyist who has the luxury of doubling you're shoot time but I'm not paid to stand around. Obviously I'd have more time shooting my landscapes but in the first or last light of the day when a minute or 2 can make a difference in the type of light, I would go ballistic if I had to wait after each exposure. I mean why do they advertise the frame rate of the back when it is completely dependent on the exposure time on the view camera.

I love the look of the camera but this is the main reason why (and the issues with Schneider lenses) I wouldn't change to a Phase One System at the moment. When I read the 1hr exposure limit I almost had a hear attack. It would be ideal for a project I want to develop. Aw well

Doug Peterson

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #146 on: March 11, 2013, 03:33:14 pm »

How can a ground glass be just fine for an 80MP sensor and no good for a 200MP sensor that is a multi shot from a 50 MP sensor. The 80MP sensor actually only
has 36.81 % less resolution than a 200 MP MS and that is only if the lens still out resolves the 200MP capture.

I don't think Torger was specifically referencing the H4D-200. I think he was using "200mp" as an abstract reference to "even higher resolution".

Also, I don't really want to get involved in a discussion of resolvable feature size on ground glass. I almost always fall back on the "try it yourself" argument but I think that especially applies to ground glass focusing. That said, I do want to point out that you don't actually need to have a resolveable feature size that matches the pixel size of the back you're using. When focusing most camera systems (of any kind/make/model) there is some range of focus travel in which the subject remains equally sharp in appearance. For some camera systems this range is quite miniscule (a Canon 5D3 with a 24-70m1 in my experience is like this) on other systems with more precise (read: higher barrel travel vs. lens movement) focus systems the range is quite large (e.g. and Arca Swiss R series with it's very large focus bayonet and fine-gearing). Whatever that range is, a very high-confidence estimation can be made that the perfect point of focus is half way through that looks-the-same focus range.

Doug Peterson

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #147 on: March 11, 2013, 03:39:02 pm »

The argument that because the base exposure is greater doesn't do it for me I'm afraid. If I had to wait 1 hr I'd be pissed off. If I had to wait 20 minutes I'd be pissed off. If I had to wait 256 seconds I'd be pissed off.  :) For a lot of people who earn from photography it would be a waste of time. Grand if you are a hobbyist who has the luxury of doubling you're shoot time but I'm not paid to stand around. Obviously I'd have more time shooting my landscapes but in the first or last light of the day when a minute or 2 can make a difference in the type of light, I would go ballistic if I had to wait after each exposure.

Well... ok. But no matter what you have to wait some period of time (e.g. a 2 minute exposure without a dark frame still requires you to stand around for 2 minutes doing nothing).

If you can take the shot in 2 minutes with Camera A, which only requires the main exposure time and you can take the same shot in 1.5 minutes with Camera B, does it really matter if Camera B was doing a dark frame during part of that time?

Enda Cavanagh

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #148 on: March 11, 2013, 03:49:55 pm »

Well... ok. But no matter what you have to wait some period of time (e.g. a 2 minute exposure without a dark frame still requires you to stand around for 2 minutes doing nothing).

If you can take the shot in 2 minutes with Camera A, which only requires the main exposure time and you can take the same shot in 1.5 minutes with Camera B, does it really matter if Camera B was doing a dark frame during part of that time?

Ah If I was taking a photo for example a panoramic photo consisting of 2 sets of images, that would have a huge difference. For example the light may change, clouds will have moved significantly many things may have changed. Ditto for a single view with under normal and over exposed exposures. Not everywhere in the world has nice blue skies for the entire day. For panoramic the light and clouds (if present must run smoothly from one side of the panoramic to the other)

chrismuc

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #149 on: March 12, 2013, 01:40:06 am »

Doug, a question regarding the iPad resolution.

From my understanding, only the partial image which is actually viewed on the iPad will be converted in the IQ2 backs from raw to jpg and transmitted via Wifi to the iPad app. For an iPad mini and the older iPads that would be a partial image of 1024x768 pixel size. Is for an iPad retina an image of four times that pixel count = 2048x1536 pixel calculated and transmitted? If yes, does this cause a relevant delay compared to the 1024 iPads?

Thx Christoph
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FredBGG

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #150 on: March 12, 2013, 01:58:36 am »

The argument that because the base exposure is greater doesn't do it for me I'm afraid. If I had to wait 1 hr I'd be pissed off. If I had to wait 20 minutes I'd be pissed off. 

The whole dark frame thing is a pain. One should also consider the reliability of the dark frame being effective.

When a dark frame is made there is the assumption that it will record the same noise that was recorded during the photo exposure.
However is this going to be the case. The fact that a dark frame has to be recorded right after taking the photo shot means that it will be an attempt at recording the same noise pattern.
Changes in temperature and other things that produce noise could alter the recorded noise.
If that were not the case then one should be able to simply use a previously saved dark shot file.
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bcooter

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #151 on: March 12, 2013, 02:23:14 am »

The whole dark frame thing is a pain.


Fred.

Is this  theory or something you discovered in practice?

The only dark frames I've shot with seriousness are background plates with my M-8 Leica and they worked very well.

This image is a work in progress, soon to be a cinematic.



The Background was with the M8, the inserted photo my p30+ back.



Do you have any long exposure frames YOU shot with your Phase One back?

Do you have any compelling images you can show that you shot with any digital camera?



IMO

BC
« Last Edit: March 12, 2013, 02:46:25 am by bcooter »
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torger

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #152 on: March 12, 2013, 02:41:35 am »

Are you claiming that a ground glass focusing screen can resolve  9 or 10 microns...... ?

Here's an actual photo:http://www.ludd.ltu.se/~torger/photography/img/dwcf-fs.png it's of the ground glass and the resulting 33 megapixel image. It's grainy, but you actually see the individual dashes on the mm-scale of the folding rule. The 18 megapixel estimation is no scientific measurement, and probably a little bit exaggerated, the point is that you see detail through the grain, just as with film.
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ErikKaffehr

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #153 on: March 12, 2013, 02:45:02 am »

Hi BC,

Dark frame exposures are a pain weather you shoot Phase One or Sony. You wait for an extra exposure that is used to reduce thermal noise. If you are concerned about writes times on the Pentax you would also be concerned about dark frame exposures.

Now, dark frame exposures are for a reason. On some cameras you can disable, it is possible on Sony I don't know on Phase.

So, I'm with Fred on this one but I don't see it as matter of Phase vs. something else. It's PIA of digital.  With film we had reprocity failure, that was PIA of film.

Best regards
Erik


Fred.

Is this  theory or something you discovered in practice?

Do you have any long exposure frames YOU shot with your Phase One back?

Do you have any compelling images you can show that you shot with any digital camera?

IMO

BC
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torger

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Re: resolution limits of the secondary image scattered off the ground glass
« Reply #154 on: March 12, 2013, 02:48:50 am »

How can a ground glass be just fine for an 80MP sensor and no good for a 200MP sensor that is a multi shot from a 50 MP sensor.

With higher resolution you tend to want to shoot with larger apertures to avoid killing resolution with diffraction. With larger apertures and higher resolution the exact position of the focal plane becomes more clear when you pixel peep, i e you require higher precision. However, if you still choose to shoot at f/11 with you 200 megapixel back as you would with a 40-60 megapixel back, it will be okay. When/if pixels become cheap it can be a good idea actually, outresolving diffraction to minimize aliasing issues.

I think ground glass is good to f/11. If you want to shoot f/8 or f/5.6 it is too high risk to miss. If you do it only occasionally and shoot tethered it's okay anyway since you can see any miss on the computer and compensate, but if it is part of the main work I'd choose an Arca-Swiss RM3Di or Alpa and a laser distance meter.
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bcooter

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #155 on: March 12, 2013, 02:48:54 am »

Hi BC,

Dark frame exposures are a pain weather you shoot Phase One or Sony. You wait for an extra exposure that is used to reduce thermal noise. If you are concerned about writes times on the Pentax you would also be concerned about dark frame exposures.

Now, dark frame exposures are for a reason. On some cameras you can disable, it is possible on Sony I don't know on Phase.

So, I'm with Fred on this one but I don't see it as matter of Phase vs. something else. It's PIA of digital.  With film we had reprocity failure, that was PIA of film.

Best regards
Erik


I understand, I've only done 8 seconds on the Leica and for backgrounds haven't found it too much problem, though I rarely stitch.

My point is the theory of the dark frame possibly not working was mentioned by someone that never shows images they shot in those situations.

Thx.

BC
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Doug Peterson

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #156 on: March 12, 2013, 10:17:02 am »

Doug, a question regarding the iPad resolution.

From my understanding, only the partial image which is actually viewed on the iPad will be converted in the IQ2 backs from raw to jpg and transmitted via Wifi to the iPad app. For an iPad mini and the older iPads that would be a partial image of 1024x768 pixel size. Is for an iPad retina an image of four times that pixel count = 2048x1536 pixel calculated and transmitted? If yes, does this cause a relevant delay compared to the 1024 iPads?

That is correct.

However, Phase One is considering a button in Capture Pilot to push to drop the Retina iPad down to non-retina resolution. This would have two benefits:
- speed will increase by around a factor of 4
- when viewing at 100% the pixels will be easier to see (at Retina resolutions you may wish to slide to 200% to carefully evaluate the pixel-level detail/sharpness depending on your eye sight)

I'm anticipating the iPad Mini being the ideal balance of resolution, portability, and size. However, everyone's needs will vary.

Paul2660

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #157 on: March 12, 2013, 10:40:32 am »

I have worked with Nikon, Canon and Phase all with long exposures, some totaling up to 55mm. 

Nikon and Canon on their higher end cameras offer a dark frame, both will allow you to turn it off.  When you stack, it's imperative to turn it off as the resulting dark frame will create a gap.  Gaps can be closed in software, but it's an added step that sometimes has trouble depending on the camera lens combination. 

It's always been my understanding that the dark frame is more to reduce "stuck Pixels" rather than traditional noise.   Stuck pixels will increase over time of exposure and can ruin a frame.  Some cameras will show them red, blue other pure white.  Either way, they have to be removed before you can run a stacking solution or just from a single long shot.  Your DSLR's are all CMOS and thus tend to be a bit less noisy on longer exposures.  You still have to watch for heat (both in camera from longer run times and ambient outdoor temps and humidity).

When shooting Canon or Nikon I really don't notice any noise difference with Long Exposure noise reduction turned on.  On a short stack say 2 min to 4 min, I will start to see a few stuck pixels over the course of a nights shoot, but nowhere near as many as when I do a single long exposure.   It's very easy to test this by taking two single long exposures, say 20 minutes, one with Dark Frame on, one without.  The image without LEN on will more than likely will show considerable stuck pixels, the other should be clean.  In the old days, before this was available, you always had to shoot one shot with the lens cap on of the same length of exposure then reduce the stuck pixels manually.  Never worked as well for me.  Also the longer a camera runs, 1 hour, 2 hours, etc. the more stuck pixels tend to show up and most times they are not in the same place each time, thus the need for the internal software (in camera) to remove them.   

Since the 5D MKII, Canon has allowed you to run the long noise in the background i.e. buffer.  So you could take usually 3 30 to 40 min long exposures before the buffer locked you out.  Nikon works just like Phase One (except you can't turn phase off), shoot 1 frame and you are locked out of the camera until the dark frame is written.  Before I shot all stacks I preferred Canon over Nikon for this simple reason, i.e. you could get a lot more done in one night before the camera buffered out.

Some of the raw converters can remove some of the stuck pixels, like LR, but I have only found this to work if the image capture is raw.  With a jpg, then they are truly stuck.  Since most people seem to still shoot jpgs I think this one of the reasons the large camera companies added this feature.

Phase one, with at least the P45+ seemed to do a bit more than just remove the stuck pixels and the dark frame that camera ran IMO was more critical to the end result.  Doug or others closer to design by Phase would know more about this. This is CCD and the Dark frame may be more critical to the end result. 

Paul Caldwell
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Enda Cavanagh

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #158 on: March 12, 2013, 11:01:36 am »

Hi BC,

Dark frame exposures are a pain weather you shoot Phase One or Sony. You wait for an extra exposure that is used to reduce thermal noise. If you are concerned about writes times on the Pentax you would also be concerned about dark frame exposures.

Now, dark frame exposures are for a reason. On some cameras you can disable, it is possible on Sony I don't know on Phase.

So, I'm with Fred on this one but I don't see it as matter of Phase vs. something else. It's PIA of digital.  With film we had reprocity failure, that was PIA of film.

Best regards
Erik


Hi Erik
I shoot on a Hasselblad back with a Cambo. You don't need to shoot a dark frame. I can squeeze  about 90 seconds out of the exposures on the view camera (Don't ask me how because the official limit is 60 seconds :D) After that it times out. If the exposure is correct than noise is not an issue as are stuck pixels. ( Occasionally I get the odd one)

This was the reason I went with the Hasselblad. Doug made the argument that the limit on the new IQ260 is much longer and that is true but about 60% of my photos are between the 1 second and 90 second range. The rest are faster and obviously if I could shoot longer that would open some lovely new doors of opportunity. My point is the vast majority of the time I would be able to shoot images within the 90 second limit each time not having to double my waiting time for my exposures.

Doug made a very valid point that it would be a good idea if Phase were able to limit the use of the dark exposure after a certain exposure time, so that say it's not needed until after a minute or 2. That should be possible. If Hasselblad can do than I don't see why Phase One can't do it. That would move the goal posts for me ( I have to test the H5D 4D or H5D 60 yet to see if there is an issue with the Schneider lenes also and I'll post my findings. That is the other stumbling block  :))

MrSmith

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Re: Phase One IQ260, IQ280, and Achromatic - 11 Things to Know
« Reply #159 on: March 12, 2013, 12:33:34 pm »


Doug made a very valid point that it would be a good idea if Phase were able to limit the use of the dark exposure after a certain exposure time, so that say it's not needed until after a minute or 2. That should be possible. If Hasselblad can do than I don't see why Phase One can't do it.

they don't always do what the end user wants.
Hblad and the HY cameras both do focus stacking but the new phase backs/cameras/software do not. surely these kind of features would be seen as essential if all the competition have enabled it? 
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