How Big Is Too Big?

[BJL]

WHY DO THE OLYMPUS 8MP 4/3RDS CAMERAS NOT SHOW THIS GREATER ACCUTANCE WHICH ONE WOULD EXPECT FROM THE SUPERIOR ZUIKO LENSES?
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What evidence of accutance comparisons are you looking at? The only resolution comparisons I have seen are at the opposite extreme from accutance/contrast, being comparisons of "extinction resolution". What is more, these are based on comparisons of standard JPEG output from different cameras. This means that sensor performance, low pass [AA] filter performance, Bayer interpolation algorithms, and JPEG conversion algorithms are all affecting the results, obfuscating attempts at pure lens to lens comparisons. (Comparing image quality with results from different cameras, one far older and/or cheaper than the other, would be a rather unscientific way of comparing lens performance.)

[Lin Evans]

That sounds interesting, can you tell us more about this software?

By the way, I stitch shots all the time with a Phase One P25 on a large format camera, there's several manufacturers now making "sliding carriage" backs for large format cameras. You basically attach the digital back to the carriage and shuffle it around inside the image circle, you don't need software to bring the frames together, the sliding carriage handles it all with pixel accuracy.

I use it for architectural work where it's a breeze. Even if there's people or cars in the shot unless they're actually straddling the dividing line it doesn't matter, even then you can Photoshop them out. The only really tricky problem is when photographing a building across water, then stitching becomes a marathon Photoshop exercise in blending in waves and ripples. But for a 20" x 30" print this delivers the goods with sumptious, "nose to the print" quality.
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Hi Gary,

The software was originally designed for photomicroscopy and there are several versions available from extremely expensive to free. The one's I'm familiar with are listed below with links. Of these three I use Helicon Focus (moderately priced) and Combine Z (freeware - donations accepted).

First, the very expensive but very powerful Auto Montage by Synchroscopy. This software does it all, but is out of the range for most except for the university academic or scientist who has a large budget for equipment and software.

[a href=\"http://www.syncroscopy.com/syncroscopy/am.asp]http://www.syncroscopy.com/syncroscopy/am.asp[/url]

Next is Helicon Focus - very powerful, almost as powerful as Auto Montage if you buy the "Pro" version. It even allows for a dust map to automatically remove (clone out) sensor dust. I use this one most....

http://heliconfilter.com/pages/index.php?id=509

Finally CombineZ which is also quite powerful but a little more difficult to use.

http://www.hadleyweb.pwp.blueyonder.co.uk/CZ5/combinez5.htm

Any of these products will do the job of combining same frame with differential focus points into an "infinite" focus single image. The differences are in how well they can handle "registration" (the slight shift in size of the image when choosing differential focus points). There are a few "caveats" you need to keep in mind when using these for hyperfocal landscapes - things like not having a huge tree six inches from the lens with mountain wildflowers three feet in front - etc. You will quickly get a feel for the possible, probable and impossible when doing this. If you are interested I think I still have a sample somewhere which I posted a year or so ago showing a digicam on a tripod about a foot from the lens with focus continuous from this spot to mountains several miles distant. Let me know and I'll dig it up. It shows the pitfalls and promise of this technique.

addendum:

Actually I just looked and found a link where I posted this test on the Helicon Focus forum. Here's the link if you want to see the original and combined frame.

http://helicon.com.ua/forum/viewtopic.php?t=121

Stitching:

Yes, stitching is definitely the poor man's BetterLight scanning camera. It offers a way to dramatically increase resolution while maintaining perspectives which are impossible to get with the same system and any wide angle lens. It's always great to see a stitched wide angle or panorama without nearby trees leaning in at an obtuse angle which would be the result of using a normal wide angle lens on a 35mm platform. I often look at excellent landscapes such as those done by the late Galen Rowell where this issue detracts from an otherwise incredible image. I suspect if Galen and Barbara were still alive today they would be shooting with a Canon 5D (he always loved lightweight camera bodies) or even a Nikon D2X and stitching to get some of those fantastic images he used to get with the little Nikon 35mm film bodies.

Best regards,

Lin

[Ray]

What evidence of accutance comparisons are you looking at?

BJL,
I'm looking at the standard studio shots at dpreview here

You'll notice in these shots of 'real' items, the Olympus E-500 has a slight advantage because the wider-aspect-ratio EOS 350D has been matched with respect to picture height. Despite this slight disadvantage of the 350D, it manages to deliver 'crisper' images than the E-500.

Both these cameras have the same pixel count (approx). The Olympus has the advantage of a better lens as well as the advantage of slightly more pixels in the vertical dimension, yet the 350D produces slightly better images with apparently greater accutance. This is particularly noticeable in the blow-up of the Leica lens featured in the studio shot.

What is more, these are based on comparisons of standard JPEG output from different cameras.

It's true that having only jpeg images to compare tends to obscure the results somewhat, if one wishes to put a really fine point on the matter. However, I've never heard the argument that a reason for shooting in RAW mode rather than jpeg is that all one's fine prime lenses will be rendered as mediocre zooms in jpeg mode.

Of course, it could well be the case that the finest quality jpegs the E-500 can produce simply do not do justice to the camera and that Canon have simply done a better job with regard to the 'fine quality' jpeg output of the 350D. If this is indeed the case, then point me to the evidence.

I can draw conclusions only from the evidence in front of me.

[Gary Ferguson]

Lin, I've ordered the Helicon product, thanks for the tip.

[Dr. Gary]

Eric, I'm afraid we're going to have to agree to disagree on this point. In the earlier days of digital we were mainly limited by the number of pixels at our disposal. So it made sense to measure enlargement capabilities just in terms of pixels, using the 240-360 dpi measure that you referenced. However, we're now getting to the stage IMO where we have to temper that simple linear relationship with some other factors.

Let me give you one example, depth of field. The DOF engravings on manual focus lenses were established in the 1930's, apart from the ASA/ISO standards for film it's one of the few examples where the photographic industry has ever agreed on anything! Rather than have different lens and camera manufacturers competing on who's products gave the greatest depth of field they agreed on a convention that said the image recorded on 35mm film would be considered as "in focus" if an infinitesimal spot in the subject was rendered in the negative as a "blur circle", or "circle of confusion" no more than about 0.030mm in diameter. There was in fact some departure from this standard, Leica engraved their lenses to a slightly more rigorous depth of field standard of about 0.025mm. But basically the convention has held for the last 70 years.

And if you enlarge a 35mm negative say x4, to get the common 4"x6" print, then it's a pretty good guide. That will render the point in the subject as a little blur circle about 0.1mm in diameter. Not quite up to the standard you spoke about but pretty good. And in the good old days of silver darkrooms 35mm enthusiasts like myself regularly achieved really sharp and satisfying 10"x8" prints, and on rare occasions with a really lucky negative we could even go a bit larger.

[/But suddenly with 11MP, 12MP, and 17MP DSLR's we seem to think that we can enlarge to x12 or x15 with impunity. Well, that takes the blur circle on the print up to about half a millimetre, and even to my middle aged eyes that just looks plain soft! Let alone guaged against the stern standards you've advanced for the limits of resolution].

Let me give you a practical example. Here's a 100% crop from a P25 back with a Hasselblad 100mm lens, it's precisely focused at a distance of 10 metres at an aperture of f11, no sharpening, no nothing.

In the second shot I've shifted the focus by turning the 10m focus mark around the lens, not to the f11 position that Zeiss/Hasselblad say is acceptable, but just a little way to the f5.6 position. So two full stops more restrictive than the recommended DOF limits. To my eye it looks like rubbish!

This is why I say that we've now moved beyond pixel limited enlargement barriers, and we're basically back to the same physical and optical constraints that have capped our photographic ambitions for the last seventy years.
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All I know is that I have a 24x36 enlargement of a Ukrainian hotel I took at night with my 1DS Mk II , using a Canon 135 f/2and can see a tie on a person standing in the window of the hotel 3/8 of a mile away. I have some enlargements made with my 50 1.4 that blow me away.

drgary

[Ray]

...with my 1DS Mk II , using a Canon 135 f/2and can see a tie on a person standing in the window of the hotel 3/8 of a mile away.
drgary
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It's a pity you didn't have a 5D with you at the time. I'd love to see how that tie would look in a 5D shot   .

[BJL]

BJL,
I'm looking at the standard studio shots at dpreview
...
I can draw conclusions only from the evidence in front of me.
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With that evidence from in-camera JPEGs at default settings, you can draw no conclusions at all: famously, different approaches to level of in-camera sharpening, AA filters and such make these images useless for comparing the resolution of lenses, or even or of sensors, at least when the results are vaguely close.

For example, my E-1 is permanently set at +3 sharpening (in a range of -3 to +5) for JPEG output; the default is quite soft.


I, as the 4/3 defence, feel no need to point you to the evidence; the "prosecution" has offered fataly flawed evidence and so not made its case. Why are you so determined to talk down a system and lenses you have never used?

[st326]

"Do some relatively large, sharp photos reveal more detail than a person would discern when looking at the actual scene?"

No question about it. I've recently started using a 4x5 view camera (Cambo Legend) with a Better Light Super 6k scan back, mostly at 8000x6000 resolution. I took some pictures from my bedroom window when setting it up for the first time, and something that looks like a 2 pixel white splodge when looking full frame is actually a completely readable road sign at 100%, and definitely not readable by the naked eye (and I have extremely good eyesight due to laser eye surgery). So yes.

What I do find though is that at sensible print sizes, the Better Light images have more resolution than my eyes can resolve in the print, too. This has considerable visual impact with some images. (understatement!)