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To Megapixel or not to Megapixel, that is the question....


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#1 Alan7140

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Posted 07 July 2012 - 03:25

A bit long, but bear with me:

In an earlier post of photos taken with a Fuji X100, the megapixel question came up, and as this is something I've been spending a lot of time contemplating recently, I thought maybe a discussion thread was worth opening up on the subject, principally concerning the D800 and alternative approaches, or indeed needs.

As some might know, owing to the improbably large files I've been generating over the past few years with multi-row stitched and focus-stacked panoramas, at the end of last year I bought a latest upspec PC, (12 cores @ 4.3GHz through 64GB RAM & SSD) which just, and I emphasize just, made working these panos taken with a D3s (i.e. 12MP files) practical. The biggest pano involved 240ºx160º field of view and comprised some 625 individual photographs, some focus stacked with up to 11 steps. It was the image that prodded me into upgrading the computer, because processing on my previous 8-core 2.66 GHz 12GB RAM machine had been impossibly slow.
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But the D3s has some drawbacks: it is heavy to carry, and on the Nodal Ninja Ultimate panoramic head it is imperative to use the mirror up function with at least a slow 2-count pause before releasing the shutter. There is no room in one of these sequences for even one vibration-affected frame. In a photo with moving objects and less than still air, the slowness of operation thus caused can become a real problem (this shot took 29 minutes to take, moving as quickly as I could).

Of course with a slow taking sequence things like a sunrise (or sunset) become something that must be planned and prejudged exactly to even work, as the earth's rotation cannot be put on pause. I think there were close to 300 shots in this sunrise, and that it worked at all still leaves me slack-jawed (took about 12 minutes to expose moving top left to bottom right, along with a three hour return hike the evening before to work everything out so the pre-dawn setup wouldn't be guesswork):
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Now enter Nikon's release of the D800E. On the face of it the extra resolution & modified anti-alias filtering was oh-so appealing (though I'm not sure why, as the human eye doesn't have a 100% function), along with the draw card of its 14+ stop dynamic range. I was on the cusp of ordering one, but delayed to allow production to bed in, and this delay let the misgivings I had filed into the "do not think about" basket bubble to the surface. My supplier's attempt to interest me in a wide-angle attachment for my Fuji X100 led me on to investigate the new Fuji Pro X1, sweetened by Fuji's promise of a Leica M mount adapter, along with a plethora of 3rd party adapters for umpteen other lens mounts.

So I took more interest in my X100 and tried to envision how a mirrorless rangefinder camera with a hybrid viewfinder might fit into the scheme of my "serious" photographic work.

Yesterday I set up the X100 on the Nodal Ninja pano head in the backyard and did a really rough 360º spherical set of exposures (74 all-up). Focus stacking is not an option with this camera given that any "manual" focusing involves turning a focusing ring which in turn has the AF motor moving the lens, which is jerky and after-thought style stupid. However a manual focus legacy lens will not have this drawback on a Pro X1.

Getting to the point of all this now was that taking the pano was simply lightning fast compared with the mirror-up~...wait~....release of the D3s. Triggered with a good old-fashioned screw-in type cable release, the only problem was not vibration (zero) but rather knowing that the camera had taken the exposure at all, the shutter being so quiet. The X1 will be louder, and this is not a bad thing in this instance. Or alternatively the sonic fake shutter sound could be set in the menu, of course. All 74 shots were completed in 5 minutes flat, including a couple of pregnant pauses where I wondered whether the shutter had gone off at all, and also fiddling with the pano head to adjust for the vertical rows. The desire for the D800E was teetering...

So to image assembly - the X100 takes 12.2MP size files. The computer had no problem with this, but the end file size was still a tad over 2GB. So the 16MP Pro X1 using a similar focal length will have one of these spherical panos using a 23mm lens in at around 2.75GB, and for a D800E we're looking at around 6.6GB by simple multiplication - but probably not all that much larger if a 23mm lens was used as the sensor covers more real estate with each shot. However this is getting ridiculous for something to be printed out at a maximum of 24" high @ 288ppi, or worse, made into a quicktime pano tour web-size movie of around 1MB. Even a 44" high print would probably be over-serviced. Have you ever tried to sell a 44"x 8' print? Very small market for this. Tiny, even. As small as the print is large.

If I were trying to enlarge a single frame to 34"x24" perhaps the D800E would make sense, but fact is that I rarely do this, and even when I have the D3s files have posed no real problems getting there. Sure, they might not hold up as well under inspection-glass scrutiny, but at a viewing distance of a couple of feet or more, no problems whatsoever. Even though using the same focal length might result in fewer photos needed overall with the D800E, if focus stacking each shot was part of the equation there would be the need to process these full-size D800E files, so a stack of 12 would involve churning around roughly 2.4GB of info in the form of Tiff files. A pano involving stacks from 1" to infinity would be a nightmare, but this is something I'm working on at the moment. Even though there'll be more individual stacks involved, the ~100MB Tiffs from a 16MP camera will be a lot more machine friendly than doing this with 36MP files. Same goes for HDR stacks.

The backyard shot below started out at 27771 pixels wide, hammered down to 1389px if expanded by clicking on the forum thumbnail further hammered down to that shown here, so forget about judging image detail & sharpness, just take my word that both are here in spades on the original (the DR is, however, very evident, and yes, I'll paint the shed one day, after I repaint the roof and everything else that a 132 year old house needs in ongoing maintenance :wink: ):
Posted Image
I had made a lo-res *.mov "tour" file of this but the website refused to upload it (format incompatible?) so the smudge bottom & top won't make sense, but the tripod is what's stretched along the bottom, and I didn't bother with either "nodal" shots to cover the tripod over or the zenith circle either.

Edit: I'll also add this 100% section (click on it to see at it's 1000px width) to back what I said about resolution and to give perhaps a better idea of just how big this image is at its native resolution, the dam & post gives the position of this away with regard to the rest of the picture (remember, this is from a 12.2MP camera):
Posted Image

Now the Pro X1 has allegedly got the best sensor ever seen in an APS-C format, and given the way that the X100 handled this rough & ready 360º shot covering deep shadow to straight into the sun (no planning at all, only the most cursory exposure reading & setting), I'd have no fear that the Pro X1 will be more than capable of even better. So I'll probably order one next week. :rolleyes:

Also the 23mm lens on the X100 is too wide for panos with minimal distortion (crop factors are meaningless here outside of the number of shots required, 23mm is 23mm which causes almost unacceptable anamorphic distortion in panos - or horizontal compression, to put it another way) - 35mm is my preferred focal length as a balance between anamorphic distortion and sheer numbers of photos required to cover the real estate, and thus also the end file size. So in fact we're talking even bigger unsampled end file sizes anyway... the first photograph at the top was taken with a 50mm lens to completely wipe out anamorphic distortion, which helps account for the huge number of shots required (aside from the stacking involved). Of course the smaller APS-C sensor on the Pro X1 will require even more shots to cover the same real estate were I to use a 50mm lens, and were I to contemplate a 4/3rds camera, even moreso again.

So assuming a 35mm lens will be the best compromise, I have a 35/1.4 AI-s which I bought brand new at end 2010 and will fit a Pro X1 via adapter, and I possibly will nevertheless also contemplate the Fuji's "standard" 35/1.4 as well for those AF-type shots away from the pano head. Whatever, the D800E would appear to be off my shopping list now as being less practical for this sort of thing.

Swings and roundabouts, nothing's ever simple, is it?

This post has been promoted to an article

Edited by Fred Nirque, 09 July 2012 - 02:13 .

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#2 azrockitman

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Posted 07 July 2012 - 04:08

Thanks for taking the time to write and post this. Very worthwhile read and I especially love the blue cast mountains in the far distance of your sunset photo. The sun is almost "blinding", as a sun should be I suppose! :good:
Tim

#3 Bart Willems

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Posted 07 July 2012 - 04:13

(...) because processing on my previous 8-core 2.66 GHz 12GB RAM machine had been impossibly slow. (...)


Oh god yes, the horror...

(written by somebody who grew up with a 1MHz TRS-80 with 48kB of memory)
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#4 Eb Mueller

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Posted 07 July 2012 - 04:54

Makes sense to me - the right tool for the job. You want something light, convenient and resistant to shake. All the megapixels of the D800 are not useful for your projects, unless you are using an ultra-wide - but, with distortion unacceptable for stitching. I only know about the Pro X1 by reputation, but if it is rugged and sealed enough for your purposes, then I'd give it a go! I'm looking forward to Nikon coming up with similar, perhaps a large sensor version of the V1.
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#5 Alan7140

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Posted 07 July 2012 - 04:56

Thanks, Tim.
The blue cast is endemic to Australia's eucalyptus forested east coast mountains (in fact the chain of mountains, the north of which this was taken, are actually named the "Blue Mountains"). The blue is caused by light diffraction through the oil and water vapour from eucalyptus trees dispersed in the form of very fine droplets into the atmosphere. The air also smells nice as a consequence.

Hey Bart, quit bragging - I lusted after one of those TRS-80's but couldn't afford one. Especially the model 111. Sleek, all-in-one, Star Trek console thing, if I recall. Looking back I cannot think of what, as a photographer's assistant, I could possibly have done with it, either. It took another 15 years before I got an Apple IIci and made my first tentative steps into Photoshop 2.5

#6 Alan7140

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Posted 07 July 2012 - 05:05

Couldn't agree more, Eb, except that Nikon are going to have to lift their game in the field and stop treating mirrorless compacts as amateur-only tools. Fuji took a brave step with the X100 - and I admit I was an instant skeptic at the time, but having owned one after a nostalgic moment of Leica IIIc deja-vu when actually seeing it in the flesh for the first time and handing over the Visa card on the spot, and further after actually completing (almost) the incredibly convoluted learning curve that it presents, like so many others I am simply smitten with it and it goes everywhere with me.

#7 Dallas

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Posted 07 July 2012 - 05:55

Post of the year, imo.

Win a thinkTank Retrospective 30 camera bag just by making a post to Fotozones this week! 

 

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#8 Alan7140

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Posted 07 July 2012 - 07:36

Thanks Dallas! :)

I've added an image which qualifies my claim about resolution and sharpness in the scheme of that backyard shot.

#9 Tejpor

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Posted 07 July 2012 - 09:40

I now see why people still shoot 8x10" and even larger film...

#10 DougB

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Posted 07 July 2012 - 13:04

Fred
Thanks very much for sharing your thoughts. I am always amazed by your beautiful panos!
Regards
Doug

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D700, D300; D200; F2, Lumix FZ30; and a bunch of Nikon MF & AF glass (& a Rokinon 85mm f1.4)

#11 Bart Willems

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Posted 07 July 2012 - 15:05

Fred, me being a panorama dilletante who only occasionaly shoots pano's -- and just using a regular tripod is already a huge step for me in those :) -- I am vaguely aware of the gigantic image sizes one ends up with. As a digital hoarder you don't want to throw out all those pixels so quickly but your comment about the small market for 44"x8' prints made me wonder.

What would be the impact on the process if the images are resized before creating the panorama? Is there a downsize to that? (If you work with straight raw files then the answer is obvious, but if not...). If the intent not is to get a 20,000 pixel wide image, then maybe starting with smaller images is worth a consideration? I know this suggestion is pure heresy, but I'm wondering never the less.
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#12 Alan7140

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Posted 07 July 2012 - 21:16

Bart, there is a provision in both the pano programs I use currently (Auto Pano Giga & PTGUI) to output the pano at a preferred nominated size, although of course this must still involve discarding of information.

While I shoot RAW, both these programs apply their own conversion in order to process the panos, but only offer the most basic external controls in this process, so I always process in ACR first, save as uncompressed TIFF and then send to the pano program. I find the results are better that way, even if it does create another space-consuming step.

As I might have mentioned elsewhere, my motives behind these panos are actually twofold - both to provide a salable print for income generation, but also to have a digital file which can be examined in closeup sections to identify plant & fungi types therein for future historical reference. For this purpose files nearing 30,000px wide are more than adequate, not needing any more resolution than that. It also keeps things manageable in compatibility terms, as despite there being some exceptions (with the list growing), there is still a problem with many applications once the 30,000px dimension or the 2GB file size are exceeded. From an archiving point of view, it is preferable to keep things as compatible as possible, of course.

As for resizing, while I've been a longtime user of Genuine Fractals (now Perfect Resize 7), the latest Photoshop image resize when simply left on bicubic automatic is better than Perfect Resize to my eye.

#13 Longhiker

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Posted 08 July 2012 - 02:52

The Pro X1 does sound intriguing with its new sensor design and the compactness. It will be interesting to see the results by someone who knows how to stand a system on its ear to extract the most from it.
There is nothing worse than a brilliant image of a fuzzy concept. - Ansel Adams

#14 jramskov

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Posted 09 July 2012 - 18:59

Very interesting post - thanks a lot!

And that sunrise pano is nothing short of stunning!
Joergen Ramskov
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#15 Alan7140

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Posted 09 July 2012 - 22:43

Thanks, Longhiker & Joergen. I guess I've been living on the ragged edge of the old saying "you can't take it with you" lately (not that I know the date or proximity of my demise, but it is sooner than it was last year... ;) ), however despite self-advice that it's time to pull the horns in at the moment, I'll nonetheless be ordering the Fuji and an F-mount adapter this morning. The purchasing power of the Australian dollar is simply irresistible at the moment (after years of being worth only around US$0.65 or €0.55, this morning it is US$1.02 & €0.83).

So whether my logic and thought processes in this are valid will soon become evident.

#16 crowecg

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Posted 10 July 2012 - 02:25

there is still a problem with many applications once the 30,000px dimension or the 2GB file size are exceeded.


Those numbers crop up quite regularly in computing - you might find that the 30,000px limit is actually nearer 32,767. If you're friendly with the software people, these limits can be overcome - next stop 2.147 billion pixels!

#17 afoton

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Posted 10 July 2012 - 11:19

The largest file I have is 45740px x 39013px. I didn't know that would be a problem with many applications. I'm glad it wasn't a problem with Gimp, as that was the application that did the most of the job for me.

#18 Jack

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Posted 10 July 2012 - 13:57

Seeing that dawn panorama as a 1400 px wide jpeg really hurts. I can only imagine what your prints must look like. (Or what it's like to be there to witness that).

Enjoy the new tools. Lots of people here will be looking forward to your results.

#19 Tejpor

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Posted 10 July 2012 - 14:34

An interesting article appeared at Luminous Landscape by Enrico Cinalli. His technique involves a 20-meter "tripod" and remote controlled panorama head/DSLR.

It appears to be a technical, down-on-the-earth article. It explains in detail the software scripting, sensor-DSLR, etc. choices.

http://www.luminous-...s/tuscany.shtml

Personally I think such very large panoramas cannot withstand close scrutiny - especially if foliage/wind, variable lighting, and other changing elements are present...

#20 Alan7140

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Posted 11 July 2012 - 06:38

Thanks, Jack - to help with imagining the full size print, here are some 1400px wide crops at 100% from the actual file I print from (click to enlarge).
Shot with a 105/2.5 AI-s lens @ f/11 @ 400 ISO, 378 shots altogether, some done twice.

Background:
Posted Image

Fore & Mid & Back ground Left:
Posted Image

Foreground Right
Posted Image

Short Middle Center
Posted Image

Quite a bit bigger here than in the 24"x48" print in which the image appears very smooth with no grain, I thought 100% might better show detail from foreground to background, covering from about 5 feet from the lens to 80km (50 miles) distance. There was some serious focus stacking involved.

HTH.
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