Microstepping....what is it?

[Brian Hirschfeld]

Sorry if this is a very newbie question, or it has been asked already, but I can't find anything on the site or online. Simply, What is Microstepping? It seems most people who talk about it talk about Imacon/Hasselblad backs, is this just another name for multi-shot (or inversely, is multi-shot another name for micro stepping). I owned a Hasselblad H3Dii-39ms and never used the MS so I don't have an experience with this, especially since most of my work is with people, and moving objects which wouldn't lend themselves to the process. I, personally would much appreciate an explanation, especially to say, what it is, what backs (if limited to a few) it can be done with, and some basic information.......thanks....

[ErikKaffehr]

Hi,

Microstepping may mean that the sensor is moved half a pixel between exposures. This would open two opportunities.

1) If fill factor is significantly less than 1 resolution may be improved, as the back would take more point samples.

2) The microstepping may work as an AA-filter, without increasing resolution.

It seems that MFDBs gain about one EV in ISO capability with microlenses, this really indicate that their fill factor is not above 0.5.

Best regards
Erik

Sorry if this is a very newbie question, or it has been asked already, but I can't find anything on the site or online. Simply, What is Microstepping? It seems most people who talk about it talk about Imacon/Hasselblad backs, is this just another name for multi-shot (or inversely, is multi-shot another name for micro stepping). I owned a Hasselblad H3Dii-39ms and never used the MS so I don't have an experience with this, especially since most of my work is with people, and moving objects which wouldn't lend themselves to the process. I, personally would much appreciate an explanation, especially to say, what it is, what backs (if limited to a few) it can be done with, and some basic information.......thanks....

[EricWHiss]

As a way of explanation, first let me say there is both multishot, and microstep.  Multishot is where the back moves the sensor such that true red green and blue information is gathered for each pixel.  The sensor is moving a pixel width to get the red filtered sensel over where the green was and then moving again such that blue filtered sensel is over the same spot.  Green is done twice.  This means that instead of using a mathematical calculation to estimate the color at that pixel, a true color value is known.   It's worth noting that having true color values for each physical location means that moire is dramatically reduced and also since there are 4 data points for each physical location some types of noise can be reduced.     That's multishot, and microstep is very similar.  Some of the older backs with 9um pixels can do a half step.  This enables a back to record effectively double the resolution in true color.  The 528CF back that I have takes something like 19 frames to build a microstep image, but the results are simply amazing 88mp in true color.   The really nice thing about microstep is that the back is still capturing images with the 9um pixel and is not limited by diffraction as early as would a single shot 80mp sensor.    IMHO - A true color file appears to have much more detail than a single shot file, and probably will have better dynamic range as well.  

[ondebanks]

1) If fill factor is significantly less than 1 resolution may be improved, as the back would take more point samples.

Even if the fill factor is 100%, resolution of sub-pixel microstepped data can still be improved, with an algorithm such as "drizzle", originally developed by Hook & Fruchter for Hubble's undersampled WFPC2 camera. Astronomers call the imaging strategy "sub-pixel dithering" in this case, and call the processing "drizzling".

Here's a research paper where I used HST/WFPC2 drizzling, prior to MEM deconvolution.

Ray

[Brian Hirschfeld]

So is this something I could do with my back? Is it simply a way of shooting and then combining in software later? or is it more?

[ondebanks]

So is this something I could do with my back? Is it simply a way of shooting and then combining in software later? or is it more?

You mean drizzling? To do it oneself can be done, shooting lots of ordinary frames - the stepping doesn't need to be precisely half-pixels at all, just some random pattern of small shifts in both x and y (e.g. 4.6 pixels and 23.6 pixels are the same 0.6 pixel shift at the sub-pixel level; the integer part is corrected for first). But all the algorithm implementations I am aware of (IRAF, DeepSkyStacker, and I think IRIS) are for images with lots of point-sources (stars) on which to anchor the registration.

What I meant really, is that it is doable in principle for everyday shots taken with a multi-shot back. But that depends entirely on whether the back's manufacturer has encoded drizzling into its software (or firmware, if the combined image is produced in camera?), and I'm sure none of them have even heard of it!

Ray

[Dustbak]

So is this something I could do with my back? Is it simply a way of shooting and then combining in software later? or is it more?

Theoretically, maybe yes. Practically I have never heard or seen anyone do that. The mentioned software in the post above mine is mostly meant for astrophotography I believe. A microstepped 88MP image is something you have to see to believe it.. .

The Sinar/Jenoptik/Imacon/Hasselblad backs are the only ones capable of doing 16-shot (microstep), moving the sensor halve a pixel is done within the back. Calculations are done in the PC by the capturing software.

I would say, if your back isn't a multishot back with microstep capability You are not able to do microstep (or multishot).

[ErikKaffehr]

Hi,

I have seen a software called PhotoAcute that is supposed to use "superresolution" by merging multiple shots of the same image. I have not tested it.


http://www.photoacute.com/

Best regards
Erik

So is this something I could do with my back? Is it simply a way of shooting and then combining in software later? or is it more?

[TH_Alpa]

Dear Brian,

The most important about micro-step has been said, but you can also have a look at this thread in which some more detailed explanation is given, and to Bart's little animation making it easy to understand, here:

animated explanation

Best regards
Thierry

[fotometria gr]

So is this something I could do with my back? Is it simply a way of shooting and then combining in software later? or is it more?

No you can't Brian, the microstep and multishot image is one of "true color", color is not a Beyer pattern related issue anymore, each pixel is shot with all R,G&B "filters". This improves color, moire, sharpness and DR, by A LOT. If one thing is to be said Brian, is that if you shoot a still with your IQ180 and you do the same shot with my Imacon 528c in 16X microstep, do ....prepare for new eyes with the later.    It's too bad this kind of an image isn't possible in single shot! In fact, if you would have used your ex-39MS in multishot 4x, you would have been very impressed. Regards, Theodoros. www.fotometria.gr