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Author Topic: Some reflections on megapixels and things - there is a real world  (Read 3662 times)

ErikKaffehr

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Hi,

Just to say I shoot 2008 vintage MFD (P45+ on a V-series Hasselblad) and Sony A7rII. I normally print at 16"x23", that is the largest cut paper format. For larger prints I print on Durst Lambda at a lab. They have a very nice service where you send the image, tuned to taste and they print it automatically with no adjustments, perfect for me.

I am basically a tripod shooter, often shooting landscape and I am often striving for optimal quality. I recently felt challenged into looking into resolution stuff.

Recent shooting experience is:

  • Sony Alpha 99 24 MP
  • P45+ 39MP
  • Sony A7rII 42 MP
  • Sony A7rII + three way shift stitch, around 80 MP


Some recent experience:

A2 sizes Alpha 99 vs P45+, no significant difference, I would say
A1 sizes Alpha 99 vs P45+, P45+ advantage clearly shows

Recently I got some challenges, so I looked into some more:

1) Sony A7rII with Canon 16-35/4L vs. Distagon 40/4 CF FLE on the P45+ at A0 size (32" x 47")

This was an interesting comparison. The Canon 16-35/4L is a remarkably good lens, at least in my picture taking. The Distagon 40/4CF FLE has shown quite a few issues at pixel peeping, but it can still make stunning images.

The Sony A7rII has 42 MP and the P45+ has 39 MP, if we crop for the same picture height they are very close. On screen, the Distagon is good at the very center, but looses image quality fast when going off center. It actually looses a lot.

The Canon holds sharpness remarkably well over most of the field, the very extreme corners are crappy. Judged on screen it is very much better than the Distagon. How would it work out in print?

I cannot print larger than A2 (16"x23"). but cropping out half the image and printing in A2 is pretty perfect emulation of printing the image at A1. So I made A2 prints of 50% crops. What did I find?

Looking at the prints from 50 cm (20") the prints were very comparable to screen at actual pixels. At this distance the P45+ image a dead ringer for the Sony/Canon combo. Just a bit off center the Distagon lost sharpness, exactly as on screen. Looking at that distance image quality was not something I would be proud of. Canon was still great.

But…

Moving back a bit, like looking at 100 cm (40") the images were actually quite similar and the P45+ may even have a small advantage.

So, is there an explanation? Abosolutely! Many sources say that 180 PPI is needed for an excellent print. That happen to respond exactly to 20/20 vision at 50 cm. So 180 PPI matches human vision at 50 cm. A 40 MP image at A0 size is pretty close to 180 PPI. Moving back to 100 cm, the resolution of human vision reduces to something like 90 PPI.

I mentioned that the P45+ images may have a small advantage at 100 cm viewing distance. A possible explanation may be that the Zeiss/P45+ combo delivers a higher MTF (fine detail contrast) at low frequencies.

Next, I looked my Planar 100/3.5 shot with the P45+ and on he Sony A7rII. The Sony I often use with an adapter (HCam Master TSII) that offers 10 degree tilt and +/-15 mm of mechanical shift. The Planar 100/3.5 is extremely sharp, at least within Hasselblad V lens programme. So I ended up with a 39 MP image from the P45+ and a 80 MP image on the A7rII, using the same lens.

What did I see? The Sony A7rII produces an 80 MP image that is remarkably clean of artefacts. The Planar 100/3.5 outresolves the P45+ widely, and it causes a lot of aliasing artefacts. Looking closely at those 50% crops at A2 size it is quite clear that the Sony image is much more clean. But, backing of a bit, human vision masks those artefacts.

So, what is the outcome? The good news are that a 39 (or 36/42/50) MP sensor can deliver stunning results at A0 size. More megapixels and better lenses will yield a better image, but it may take some pixel peeping to take notice.

So, what is my take? It is simple, optimally, a sensor should outresolve the lens. That would yield the optimum detail with minimal artefacts. But, modern sensors are so good that they can deliver decent size prints with ignorable loss of quality.

So,


  • Do I say that 39MP is good enough for A0 size prints? Yes, I do
  • Would more MP yield better prints inA0 sizes? Yes, but we would be in diminishing returns.
  • What is the major befit of more MP? Cleaner rendition of fine detail with less artefacts.
  • Is there a disadvantage with more MP? Not really if pixel size is within the envelop of modern pixel design. Smaller pixels give more accurate rendition.
  • File sizes go up with smaller pixels
[li]A system with say a 44x30 mm sensor at 50 MP may produce the same quality image as 50 MP sensor of larger size. The deciding factor is the lens system.
[/li][/list]

A small reflection…

Hasselblad may be very smart in producing a small sensor (44x33 mm) system. They can optimise lens design for that sensor size, keeping lenses small. They can count on resolution going up, there are rumors of next generation Sony sensors going to 70-75 MP in 24x36. I am somewhat skeptical, but difficult to foresee the future is…

Best regards
Erik
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Erik Kaffehr
 

luxborealis

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Re: Some reflections on megapixels and things - there is a real world
« Reply #1 on: July 25, 2016, 05:05:26 pm »

Thanks, Erik. You are a "trusted source" so your conclusions are helpful.
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ErikKaffehr

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Re: Some reflections on megapixels and things - there is a real world
« Reply #2 on: July 25, 2016, 05:09:54 pm »

Thanks Terry!

Unfortunately, it is a bit difficult to share prints on the net.

Best regards
Erik
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Erik Kaffehr
 

Sean H

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Re: Some reflections on megapixels and things - there is a real world
« Reply #3 on: July 25, 2016, 10:01:27 pm »

Thank you for the detailed post. We trust your eyes Erik!

Thanks Terry!

Unfortunately, it is a bit difficult to share prints on the net.

Best regards
Erik
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Joe Towner

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Re: Some reflections on megapixels and things - there is a real world
« Reply #4 on: July 26, 2016, 12:44:40 am »

Why is this topic in a MF/LF forum?

If Sony 35mm gear does it for you, great, but please post in the appropriate forum.
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ErikKaffehr

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Re: Some reflections on megapixels and things - there is a real world
« Reply #5 on: July 26, 2016, 01:32:47 am »

Hi Joe,

Your response is a bit ignorant, sorry to say… Here is why:

To begin with most folks being interested in large size printing discuss things on the MFD threads. So discussing large prints is appropriate on the MFD forums. Also the images here are technically MFD. The image size used are 49x37 mm and 48x36 mm. An old but very good Hasselblad lens was used for test. The 80 MP image was made as composite of three shifted images on a Sony sensor using sensor shift.  That sensor is very similar to the one used in the IQ3-100. So it is a perfectly good emulation the IQ3-100 MP cropped to P45+ size.

The 39 MP of the P45+ I have used are very close to the Leica S2/S at 37.5 MP. It has been said that 37.5 MP is enough. Don't you think it is worthwhile to find out if twice the resolution has visible benefits.

I would rather used a Leica S (typ 007), a Phase One IQ3-100MP and say my P45+ in this comparison, but I don't have three different systems to test. If you are not interested in a thread you can always jut ignore it.

Best regards
Erik
Best regards
Erik

Why is this topic in a MF/LF forum?

If Sony 35mm gear does it for you, great, but please post in the appropriate forum.
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landscapephoto

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Re: Some reflections on megapixels and things - there is a real world
« Reply #6 on: July 26, 2016, 01:41:21 am »

Why is this topic in a MF/LF forum?

Because of the P45+ on a V-series Hasselblad used for some of the tests?
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ErikKaffehr

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Hi Sean,

Thanks, but you should not trust my eyes…

Getting back to the prints, I looked again in different light. I made two prints from the 45+ with slightly different focus, very much visible on screen, not very visible in print.

What I have found is that the 80 MP image (that was made by the Sony) has more detail, but the P45+ images have a bit more snap. I tried to process the images identically. I used colour profiles generated by DCamProf, so the difference is not a profile thing. I sort of judged the images by shifting them around until I didn't know which was which, compared two of the for a certain detail, removed the looser and compared the winner with the third image.

The 80MP Sony image was the winner on the flower in the window while the P45+ images were the winners for the foreground crop.

I cannot share images over the web, but I enclose a pair of crops. These crops are made from a file resized for a 80x120 cm print at 180PPI. Viewing the crops on a 100 PPI pitch screen at say 80 cm distance should give a good indication of print quality.

The images are from left P45+ (focus on Window), Sony shift Pano (focus on flowers?), P45 (focus on flowers).

From what I have seen here, I would say that 39 MP is good enough for a very decent quality A0-size print.

Looking at the window frame, the left side P45+ image shows some colour artefacts on the window frame, the Sony image is much cleaner. The difference is visible in print, but only when looking close.

Best regards
Erik



 





Thank you for the detailed post. We trust your eyes Erik!
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ErikKaffehr

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Re: Some reflections on megapixels and things - there is a real world
« Reply #8 on: July 26, 2016, 02:37:25 am »

Hi,

Because it is about large prints and comparing 39 MP with 80MP images. The Sony sensor in the A7rII is pretty close in pixel dimensions to the IQ3-100 and the image size used is around 36x48 mm (on the Sony) and 37x49 mm (on the P45+). A Hasselblad 100/3.5 CF lens is used, one of the sharpest lenses for the V-series 'Blad'.

Best regards
Erik



Because of the P45+ on a V-series Hasselblad used for some of the tests?
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torger

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Re: Some reflections on megapixels and things - there is a real world
« Reply #9 on: July 26, 2016, 03:48:31 am »

I also feel that going past the 50MP I have today would mostly be about reducing aliasing artifacts, not really to make larger prints with more detail. My work is sort of diffraction limited anyway, and my subjects don't really need more details than I've already got.

Still I'd love to have a few hundred megapixels so the optical system would clearly be the main limiter, but I won't go there until I can have it for a reasonable price and without sacrificing other aspects. Today lens movements is important to me, and small modern pixels have proven to be limited in that regard.

We're in a middle of a megapixel race of course. When 135 has 40-50MP, medium format wants more. I think this prestige race is steering the development towards higher resolutions just as much or even more than the actual needs.

Due to the overlaps of 135 and MFD in high resolution photography I don't think it makes sense to forbid 135 tests in the MFD forum, which really is not only about MFD but about high resolution photography in general (where 135 is capable), technical cameras (which now often is used together with 135 cameras), traditional MF SLRs used with film and legacy digital backs (often with low resolution), as well as the latest highest end MFD gear. I always thought of this as a user forum, not necessarily a MFD promotion forum, and as such it's always interesting to see tests how systems compare.
« Last Edit: July 26, 2016, 03:54:47 am by torger »
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ErikKaffehr

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Re: Some reflections on megapixels and things - there is a real world
« Reply #10 on: July 26, 2016, 12:41:04 pm »

Hi,

The reason I looked into that were claims like 37 MP is enough for any size of print. I cannot say that, but it certainly looks in my eyes like it was good enough for 80cm x 120cm. My findings also agree with the suggestion that 180 PPI is needed for an excellent print.

I do also agree that the main benefit with increased resolution is the reduction of aliasing artefacts, but it seems that most posters here are less sensitive to those than you or me. Also, I mostly shoot f/11 on my P45+ and that is a bit away from being diffraction limited.

I am not sure there is a megapixel race. To me it more seems that pixel sizes shrink as design rules are getting finer. Pixel designs have also been improved a lot. The only significant advantage of large pixels is a potential for increasing DR, but DR is soon pretty high on modern designs.

Interestingly, APS-C seems to be stuck around 24 MP, that would correspond to around 54 MP on full frame 135.

The trend to mirrorless, if such a trend does exist, may be a good thing for MFD, as it may lead to more beam angle tolerant sensors. DSLRs need room for mirror so  wide angles are retrofocus designs with small beam angles. Making a compact lens on a compact camera requires large beam angles. So mirrorless may lead to sensor designs more suitable for shifts.

Best regards
Erik

I also feel that going past the 50MP I have today would mostly be about reducing aliasing artifacts, not really to make larger prints with more detail. My work is sort of diffraction limited anyway, and my subjects don't really need more details than I've already got.

Still I'd love to have a few hundred megapixels so the optical system would clearly be the main limiter, but I won't go there until I can have it for a reasonable price and without sacrificing other aspects. Today lens movements is important to me, and small modern pixels have proven to be limited in that regard.

We're in a middle of a megapixel race of course. When 135 has 40-50MP, medium format wants more. I think this prestige race is steering the development towards higher resolutions just as much or even more than the actual needs.

Due to the overlaps of 135 and MFD in high resolution photography I don't think it makes sense to forbid 135 tests in the MFD forum, which really is not only about MFD but about high resolution photography in general (where 135 is capable), technical cameras (which now often is used together with 135 cameras), traditional MF SLRs used with film and legacy digital backs (often with low resolution), as well as the latest highest end MFD gear. I always thought of this as a user forum, not necessarily a MFD promotion forum, and as such it's always interesting to see tests how systems compare.
« Last Edit: July 26, 2016, 02:07:53 pm by ErikKaffehr »
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landscapephoto

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Re: Some reflections on megapixels and things - there is a real world
« Reply #11 on: July 26, 2016, 01:03:57 pm »

I have a slightly different approach to sharpness, megapixels and prints.

First, I don't always look for maximum sharpness. For example, I like to play with depth of field and the aspect of out of focus areas is important to me. I find that MF is generally better in that respect.

Second, I don't want sharpening artefacts but I want the in-focus parts of a print to appear sharp when examined close. In practice, that means that I will need about 24 megapixels for A2-A1 and then 50 megapixels for A1-A0. I am seriously considering an H6D-100c for bigger prints. Stitching is not always possible.

Then, because in my view print size is dictated by sensor resolution, I want to use the best lens possible to minimise lens artefacts. Generally speaking (there are some exceptions), I found out that MF lenses are better than 24x36 lenses, so I use that.
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ErikKaffehr

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Re: Some reflections on megapixels and things - there is a real world
« Reply #12 on: July 26, 2016, 02:57:32 pm »

Hi,

I would not argue on any of those points. The comparison here was made with a MF lens. The difference between the shots was that one was made with a 6.8 micron Kodak CCD covering 37x49 mm and the other combined three shots with a 4.5 micron Sony sensor covering 36x48 mm (or so). The sensor was moved while the lens was fixed. So, I would expect that the differences would be:

- Different colour between the two sensors
- More aliasing on the Kodak sensor as it has larger pixels
- Higher resolution on the Sony sensor

All other things would be similar, except for experimental error. It pretty much indicates that I would not see a significant difference at A0 size between my 39MP back and an 80 MP back with same sensor area. I don't think that would contradict your findings. OK, you say 50 MP for A0, but I think 39 MP to 50 MP is not big difference (13% linear difference).

I have often seen the figure 180 PPI for excellent prints, and then 39 MP sensor is pretty close to that, that would be about 5670 pixels on the short end for 80x100 cm and the P45+ has 5433.

Best regards
Erik



I have a slightly different approach to sharpness, megapixels and prints.

First, I don't always look for maximum sharpness. For example, I like to play with depth of field and the aspect of out of focus areas is important to me. I find that MF is generally better in that respect.

Second, I don't want sharpening artefacts but I want the in-focus parts of a print to appear sharp when examined close. In practice, that means that I will need about 24 megapixels for A2-A1 and then 50 megapixels for A1-A0. I am seriously considering an H6D-100c for bigger prints. Stitching is not always possible.

Then, because in my view print size is dictated by sensor resolution, I want to use the best lens possible to minimise lens artefacts. Generally speaking (there are some exceptions), I found out that MF lenses are better than 24x36 lenses, so I use that.
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Erik Kaffehr
 
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