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Author Topic: So, how much difference does 50MP really make with prints...  (Read 28531 times)

Bart_van_der_Wolf

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Re: So, how much difference does 50MP really make with prints...
« Reply #40 on: August 01, 2015, 01:56:33 pm »

That was a great review.  I was very impressed by the comments made by average people who didn't really notice the difference with all those extra pixels, that content and interest appears to be more important.

Hi Alan,

Do note that the prints IIRC were made at 300 PPI, and maybe output sharpening was (therefore) not as good as is possible when one does have that extra, 4x as much, detail at 600 PPI to sharpen with. Of course relatively casual viewers will look more at the image itself than the technical quality of it. They will subconsciously 'experience' a difference but will not be able to put that into words.

It's a burden I happily carry with me all my life, but technical image quality is important to me because, besides showing attention for detail in preparing the image (and thus taking the viewer serious by not holding back),  it does work on the subconscious observation. Material texture adds 'life' to the subjects we image, and if done well, it's not readily noticeable but it's present, as if subjects become more tactile, but not harsh.

I remember when I did my exams for my Photographers license (was mandatory for settling as a professional photographer many moons ago), and one of the examiners who had to judge my assignments looked at my assignment 'glass'. I had shot many different subjects with glass as the main motif, but finally settled for one beautiful stained glass window. The examiner looked at the large print that I had submitted and asked me with which view camera I had taken the image. He then turned over the printed image with my negative attached to the back in a sleeve, looked at the tiny 35mm negative, and said: "Okay, next assignment ...".

Cheers,
Bart
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wmchauncey

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Re: So, how much difference does 50MP really make with prints...
« Reply #41 on: August 03, 2015, 07:02:45 pm »

https://luminous-landscape.com/canon...t-performance/
 I still haven't yet pulled the trigger on that new body...I found that treatise interesting as he
 compared it with the same body that I've used for years.

 That fact that the "normal" client, for the most part, couldn't discern a difference in printed
 images...he could and, IMHO, that matters!

 I have made a habit of photomerging images, simply to create those large images which could
 be routinely coughed out by that 5Ds.

 My questions are...would my large, merged images, equal the print IQ as might be obtained
 by that high MP body, assuming my skills were up to the task and equal pixel/dpi numbers?
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disneytoy

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Re: So, how much difference does 50MP really make with prints...
« Reply #42 on: August 03, 2015, 08:03:32 pm »

I'd say a stitched image would be sharper. The percentage of enlargement of the optical image will be far less. But you are limited to stationary objects, and occasionally, I've messed up and missed a corner.  I like both techniques.

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Georgecp

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Re: So, how much difference does 50MP really make with prints...
« Reply #43 on: August 05, 2015, 12:10:11 am »

Hello All,

I recently pulled the trigger on a 5Ds; I can say clearly that the difference in prints as small as 8.5X11 is noticeable; the difference at a print size of 11X17 is visible, and larger is more clearly visible.  At the 8.5X11 size, the difference is subtle, but real.  The print has more realism..like a contact print from chemical days of yore.  At 11x17, the images is "touchable" compared to a similar image taken with a 5D3 or 20ishmpx camera.  These are my observations...very happy with the camera.  I have had more than a few images that were handheld, 1/100 of a second, 30 or 50mm (the 24-70LII) and the IQ was outstanding.

The handling is very refined - everything works and works together...EOS concept at a high level.

For those of us who still print and enjoy the printed image, it is a real treat in a small package...

Regards,
George
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ErikKaffehr

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Re: So, how much difference does 50MP really make with prints...
« Reply #44 on: August 05, 2015, 12:46:25 am »

Hi,

What I think Keith has noted is that the higher resolution images actually have more detail, clearly observable with a loupe or using a macro lens. On the other hand it seems that the extra detail doesn't matter to viewers. On the other hand viewers can pick up thinks like differences in global contrast and small differences in composition.

This is pretty much what I have seen comparing prints in A2 size from my 24 MP and 39 MP cameras. More detail in print but little perceived difference.

My guess is that we see is that the human vision is most sensitive to medium frequency detail. The eye can resolve fine detail but medium frequencies will dominate perception, see linked figure from Wikipedia. So if we discuss detail visible at 360PPI at 25 cm, the contrast sensivity of vision is several magnitudes below maximum. To me that indicates that we should focus our sharpening efforts more on medium frequencies than actual pixel detail.


What I have observed that 12 MP was pretty good enough for A2 size prints. At my recent exhibition I had a mix of 12 MP and 24 MP images, reflecting the state of shooting irons in my possession at that time. On most images 12 or 24 MP mattered little. Could be that 24 MP or higher would make a noticable difference.

But, on one images there were a lot "dust specs". I realised that those were birds and not dust, but 12 MP was not enough to resolve them. Now, 24 MP may not have been able to resolve them either, that is just a 41% increase in resolution.

The impression I got was that the visitors placed that image #2 of all pictures at the exhibition.



This was #1:


Best regards
Erik
Hi Alan,

Do note that the prints IIRC were made at 300 PPI, and maybe output sharpening was (therefore) not as good as is possible when one does have that extra, 4x as much, detail at 600 PPI to sharpen with. Of course relatively casual viewers will look more at the image itself than the technical quality of it. They will subconsciously 'experience' a difference but will not be able to put that into words.

It's a burden I happily carry with me all my life, but technical image quality is important to me because, besides showing attention for detail in preparing the image (and thus taking the viewer serious by not holding back),  it does work on the subconscious observation. Material texture adds 'life' to the subjects we image, and if done well, it's not readily noticeable but it's present, as if subjects become more tactile, but not harsh.

I remember when I did my exams for my Photographers license (was mandatory for settling as a professional photographer many moons ago), and one of the examiners who had to judge my assignments looked at my assignment 'glass'. I had shot many different subjects with glass as the main motif, but finally settled for one beautiful stained glass window. The examiner looked at the large print that I had submitted and asked me with which view camera I had taken the image. He then turned over the printed image with my negative attached to the back in a sleeve, looked at the tiny 35mm negative, and said: "Okay, next assignment ...".

Cheers,
Bart
« Last Edit: August 05, 2015, 12:52:55 am by ErikKaffehr »
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Bart_van_der_Wolf

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Re: So, how much difference does 50MP really make with prints...
« Reply #45 on: August 05, 2015, 04:23:25 am »

My guess is that we see is that the human vision is most sensitive to medium frequency detail.

Hi Erik,

That's correct, but it is very much connected to things like output sharpening and printing at 600 or 720 PPI.

Quote
The eye can resolve fine detail but medium frequencies will dominate perception, see linked figure from Wikipedia. So if we discuss detail visible at 360PPI at 25 cm, the contrast sensivity of vision is several magnitudes below maximum.

Yes, unless we boost the contrast of the lowest spatial frequencies of the output image!!! Then we do not only see a bit more micro detail, but also the spatial frequencies from medium frequencies to those highest spatial frequencies will receive more signal/contrast. That would partly compensate for the dropping sensitivity of human vision, and the combined (boosted) input signal x CSF = output signal drop will be slower. The image subjects will look more 'tactile' as a result. Having the additional pixels at 600 or  720 PPI, helps in boosting the signal even more, without creating artifacts that would be more likely to become visible with only 1/4th of the pixels to calculate with.

That is separate from all the other cognitive processes involved in 'vision', but in a double blind test when specifically scoring on perceived detail, it should make a difference.

Quote
To me that indicates that we should focus our sharpening efforts more on medium frequencies than actual pixel detail.

The problem with that is, that we usually cannot control the viewing distance from the output. So what may be medium spatial frequencies at a proper viewing distance that allows us to take in the entire image/composition without turning our heads too much, will become low frequency detail, and high frequency will become medium frequency detail, when we get closer. That's why we need to also sharpen the higher spatial frequencies, and that will automatically also start boosting the medium frequencies. So that makes the image quality less sensitive to different viewing distances. It's like boosting the MTF curve near the Nyquist frequency, it will lift all spatial frequencies below it as well, but in a controlled gradual/monotonic way.

Figure 24 at this site shows that the contrast sensitivity for the spatial frequencies also depends on the average luminance level or viewing conditions. Spatial frequencies of 60 cycles/degree (= average 20/20 vision, younger people can do better than that) would be around 300 PPI at reading distances, and are worthwhile to boost if we want to exploit that. We can do it better and with fewer artifacts when we boost the levels with even finer detail, say 600 or 720 PPI, and the lower frequencies will smoothly follow as well.

BTW, as cited in the link above, the receptor array in the human visual system can resolve in the order of 6/1 (20/3) or ~150 cycles/degree, which one might add would roughly match the 600-720 PPI at reading distance range. However, the rest of the eye's structure (a.o. lens) will reduce that to closer to the earlier mentioned 60 cycles/degree.

Quote
The impression I got was that the visitors placed that image #2 of all pictures at the exhibition.

That may well be because they loved the scene (as they should), more than they scored it on perceived resolution, crispness, 'tactile' quality. But those qualities do help to enhance the immersive quality of being there, if done well.

At the risk of repeating myself too much, Topaz Detail does just that, extremely well (although it gets slower with all the calculations needed as sizes increase), and it not only allows to control the small details but also those 'medium' detail frequencies separately for even more control. Detail can even be locally brushed in (or out) with edge aware masking, to avoid sharpening the noise in e.g. smooth sky gradients. Every enhancement smoothly transitions between different spatial frequencies, and can be finely controlled for overall tonality, and/or additionally for shadows and/or highlights.

Cheers,
Bart

P.S. In the book, A System Engineering Approach to Imaging, By Norman S. Kopeika, there is a chapter on the "Threshold Contrast Curve". I've attached a chart from that chapter. It basically shows, translated to our print resolution challenge, that we need to boost the contrast of the highest spatial frequencies of the input signal (towards an MTF=100%) more, to offset the loss of contrast sensitivity of the human visual system's MTF . It basically peters out at 60 cycles/degree, but Nyquist taught us that we need more than twice that sampling frequency to reliably resolve (and edit) those frequencies.
« Last Edit: August 06, 2015, 04:20:34 am by BartvanderWolf »
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