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.
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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