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 Replies: 47 / Views: 6,576 |
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Pillar of the Community
 United States
4038 Posts |
They will tell you the same thing, though Rik likes to push things a little further than I do. If you read his comparison very carefully, he does show that the onset of "diffraction limitation", which is the first point at which you start to see degradation, coincides with the DLA calculated by the Rayleigh Criterion, ie it is the point at which the first null of the Airy disk falls in the center of next adjacent pixels. All is still good here, but once the main lobes of Airy disks start to overlap, diffraction blur begins to show up.
There are probably four reasons you don't see any issues:
1) You're shooting at a magnification that is low enough to not see the problem until perhaps f5.6 (nominal aperture) on your camera. What aperture do you shoot at?
2) Your 24MP Nikon, while it has no AA filter, does not have EFSC. Thus at pixel level you may be limited by shutter shake causing enough blur to obscure diffraction effects until a smaller aperture than would be required due to diffraction alone.
3) You may not be looking at 100% crops
4) You may not know what to look for
I'd really like to see some 100% crops from your D7100 that show you don't have any diffraction problems. Only way to show it is to do the aperture sweep SD suggests. Also, if shutter shake is limiting you, you will need to either do flash or delayed continuous lighting shots to eliminate the problem.
Please, let's see the shots as I would like to come to agreement on this.
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Moderator
United States
23522 Posts |
Ray has already proven that the lack of EFSC introduces shutter shake prominent enough to obscure diffraction; it was the process which led to us settling on Canon because of EFSC. The difference was that stark.
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Pillar of the Community
United States
627 Posts |
Unless you're printing coin images the size of the side of a building, 50MP starting size is worthless...and for images that require stacking of even 2-3 images, all of the software has to just "hump" that many pixels and work that much slower to get a final product. More MP is great for marketing -- not so great for actual final quality at sizes that normal people need.
How about a global electronic shutter with no moving shutter parts? Heck even a completely electronic rolling shutter is fine for macro work as my subjects aren't moving. That would be useful...particularly on a mirror-less camera (heck, maybe it already exists on some model of camera and I'm just out of the know).
I think more interesting than increasing pixel density are the advances being made in plenoptic cameras. If I understand the technology correctly, you are able to take images and then "focus" them afterwards, which for macro photography has huge ramifications in that you can take one image, and then create a perfectly focused "stack" from the many-lens impressions. Of course behind the scenes, plenoptic cameras function like a fly's eye sort of, and give you multiple focus planes in one "shot" -- but really, it's an array of multiple smaller images focused on your sensor, and then pasted together by software post-hoc.
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Pillar of the Community
United States
4132 Posts |
When shooting at roughly 1:1, my images get softer if I stop down further than f/5.6. It's an 18 megapixel APS-C camera. I don't open any wider because I already don't have the whole coin quite in focus at that aperture (which shows up as color shifts in low/high parts of the coin due to long-CA) and I don't want to focus stack for everyday whole-coin images. I would love to say that diffraction wasn't limiting the resolution of my images, because that would mean I could maybe step down to f/8 or something and benefit from greater depth of field.
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Pillar of the Community
United States
4038 Posts |
To help with understanding of what diffraction looks like and the effect on the image, I did an aperture sweep with the 105mm Printing-Nikkor at 1:1 magnification. Here are the shots: f/2.8, effective f/5.6  f/3.3, effective f/6.6. This is right at the DLA of the 18MP sensor, and is the optimum aperture for the 105PN. This is the reference for comparing with the smaller apertures.  f/4.0, effective f/8. Just beyond the DLA, and you can start to see color changes indicating merging of pixels.  f/4.7, effective f/9.4. More color changes.  f/5.6, effective f/11.2. More color changes and starting to see sharpness degrade.  f/7.1, effective f/14.2. Fine color details nearly gone and sharpness degrading further  As you can see, the effects are subtle, and you need to know what you're looking for. First thing to go is color. Basically, the contrast between pixels is reduced such that a red pixel next to a blue pixel start to merge into two red-blue pixels. By f/7.1 the subtle color details are gone, and green channels have merged so much that inter-pixel contrast is reduced, resulting in what we all know as "diffraction blur". By f/7.1 (effective f/14.2) the camera has been reduced to nearly 4.5MP, ie the blurring is severe enough that we could capture nearly the same image with a 4.5MP sensor. Edited by rmpsrpms
02/04/2015 1:51 pm
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Pillar of the Community
 2087 Posts |
I don't have a Nikon APSC I have a sony A65 with Anti Aliasing filter but with EFCS. With the A 65 I shoot at 5.6 With that camera I use a Sigma 105mm 2.8 and for close ups the Schneider Kreuznach Iris Makro 50mm 2.8. The Sk is a recent purchase and on the A65 it performs brilliantly at 5.6. My issues with the A65 is the AA Filter and the beam splitter. The beam splitter is heaps better than a moveable mirror but it drops the effective lens speed( from memory its a 30/70 design but I could be wrong).
On the sony A 7r the SK works extremely well at F8. But to use the Sigma I am using an an adapter that incorporates that beam splitter. I am waiting for the reviews on Sonys new FE 90mm F2.8 mm G macro. If it gets bad press I would resort to either the Nikor printing 105mm or the SK Makro Iris APO 90mm. The SK is the more modern and cheaper than the nikor.
I have two perfect cameras I want: An Sony A7r with an EFCS (Or any brand as long as it is mirrorless at least 36mp) or, and my wife would hit the roof If I got it;( who needs a house?), the ultimate "Mirrorless" camera, an Alpa FPS with a Phase one back( 80MP would be nice but 60MP would do and is a little more affordable). My Alpa fantasy would include, for Macro, the Mamimya 645 140mm macro with integral shutter: The Alpa FPS has multiple cable connectors ).
As an aside I am looking at mounting a shutter on my bellows to get around the lack of an EFCS.
Why Mirrorless..... because you can mount and use nearly any lens ever made without resorting to speed boosters
The 50MP sony or canon will probably do what I want at around F5.6 the pixel size is larger than my sony A65!
Edited by austrokiwi
02/05/2015 02:02 am
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Pillar of the Community
United States
4038 Posts |
Quote:
I have two perfect cameras I want: An Sony A7r with an EFCS (Or any brand as long as it is mirrorless at least 36mp) or, and my wife would hit the roof If I got it;( who needs a house?), the ultimate "Mirrorless" camera, an Alpa FPS with a Phase one back( 80MP would be nice but 60MP would do and is a little more affordable). My Alpa fantasy would include, for Macro, the Mamimya 645 140mm macro with integral shutter: The Alpa FPS has multiple cable connectors ). Yeah, yeah, dream on! For some reason I thought you had picked up a D7100. Which of your cameras is 24MP? You can get around the lack of EFCS/EFSC by using flash. It's not so convenient for coins but it does work, and helps in other areas as well such as reducing stand vibration problems. How are you dealing with the long working distance of that SK? You'd have a similar problem with that Mamiya. Plus, large format lenses are not known for their sharpness. They don't really need to be as sharp when used for their intended purpose. What is the pixel pitch on the 80MP and 60MP Alpas? I know very little about the large format world, as it has always been beyond my reach. BTW, let me know if you decide to pick up a 105mm Printing-Nikkor. I have an extra one... |
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Moderator
United States
23522 Posts |
Pixel pitch on the 80MP is 5.4 and for the 50MP it's 6.0. It'd buy a little aperture or magnification, but a 50MP image from a Medium back is going to be the same size on your screen as a 50MP FF image so the expense is unjustifiable. No use for a Medium unless it's well over 100MP, providing the extra pixels which the extra size ought to.
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Pillar of the Community
2087 Posts |
Quote:
Which of your cameras is 24MP sony A 65 is 24mp: I would nickname it plastic fantastic when I have been using the A7r for a while going back to the A65 is weird the camera is too large and too light in weight all at the same time( I have small hands) Quote:
How are you dealing with the long working distance of that SK? You may be confusing the 50mm with the 210 Large format SK enlarger lens I tried out. The 210 is, in practical terms, unusable for coins as the working distance is way too long. Its going to get a work out in the spring with insects. The SK 50mm F2.8 Macro Iris has a very close in working distance about 10 cm max at lowest magnification. Its shape is such that a couple of Janco's can illuminate coins at 4 X magnification( working distance is down to 5cm) easily. It is a phenomenal lens for resolving tiny detail. As it is designed for assembly line imaging of micro circuits etc thats exactly what you expect. Edited by austrokiwi
02/05/2015 11:04 am
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Pillar of the Community
United States
4038 Posts |
On top of needing lenses with very large coverage, you also need even higher magnification! Does it result in diminishing returns?
Assuming same pixel size...
Let's say you're at 1:1 on APS-C at f/4, effective f/8. You are just over the edge of the DLA.
Going to FF you need to be at 1.5:1 to get same frame coverage. Your effective aperture is now f/10 and diffraction is setting in.
Taking it to MF, you need to be at 2.7:1 magnification, and effective aperture is f/14.8. You just reduced your pixel count by a factor of 4!!
Contact me for photographic equipment or visit my home page at: http://macrocoins.com |
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Pillar of the Community
2087 Posts |
Yep its not surprising I get frustrated at times with the equipment I try different methods...Medium format, for me is just a fantasy when a decent digital back costs €48,000. But you have to love that Alpa 12 FPS ( only a mere US$8000,00 without a lens or back lol)
When I am using magnification levels of 4-5 times I am dealing with only parts of the coin( mint mark, mint signature or engravers tooling marks etc) so I am stacking of course....When I am imaging a whole coin, most often thalers, I am using 1-2 (may be just a little more)
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Pillar of the Community
2087 Posts |
Well the announcement is out on the canon 5DS and 5DR: It has me scratching my head. The "R" actually has a AA filter...just that its been modified to not work( simplifies manufacturing process) The big fail no EFCS...the Nikon D810 seems to be still on top ( from my point of view)
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Moderator
United States
23522 Posts |
They sound like two very tightly-focused (snerk) instruments, designed for jobs other than ours.
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Pillar of the Community
United States
4038 Posts |
Contact me for photographic equipment or visit my home page at: http://macrocoins.comEdited by rmpsrpms
02/06/2015 11:43 am
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Pillar of the Community
United States
4132 Posts |
Apparently the 5DS *does* have EFCS (I've now heard this from multiple sources, and folks at Canon seem to be confirming it): http://diglloyd.com/blog/2015/20150...shutter.htmlLack of low-pass filter and EFCS makes this a bit more interesting, but I guess the 5D MKIV is going to be a separate model, so I'd like to see what that has in store. |
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Posted 02/04/2015 09:44 am
