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SK 35&55mm/IQ180 vs Pentax 28-45mm/645Z test and A7RII 90mm macro..Must Read!

Bill Caulfeild-Browne

Well-known member
Very interesting thread with lots of sensible comments!

My only contribution concerns the use of f14. I have tested my SK 35 LS extensively. It is sharpest at f5.6 and f8. F11 shows very minor deterioration due to diffraction, but after that things definitely get soft. I would not choose to use this lens at f14 if the ultimate in resolution is required.
 

Dan Santoso

New member
Hi Bill,

Will 5.6 or 8 render all depth of field sharp on such a scenery above?


Thanks

Very interesting thread with lots of sensible comments!

My only contribution concerns the use of f14. I have tested my SK 35 LS extensively. It is sharpest at f5.6 and f8. F11 shows very minor deterioration due to diffraction, but after that things definitely get soft. I would not choose to use this lens at f14 if the ultimate in resolution is required.
 

ErikKaffehr

Well-known member
Hi,

I guess the posting says a couple of things:

  • The Pentax 645Z performs on par with IQ-180 within it's resolution limits.
  • The zoom lens seems to be performing very well (which is the reason to check a corner)
  • So you can make significant savings if you don't need the 80 MP

What I would add is that with f/14 there is significant diffraction in the play. The Pentax would have a larger DoF (due to crop factor / shorter lens), so it could be shot at f/11 thus having somewhat less diffraction. On the other hand, diffraction can be corrected for by sharpening and no resolution will be lost at f/14.

I also agree mostly what you say about print sizes. I had a small discussion about demosaic artefacts I have observed in Lightroom on one of my Sony A7rII images with Mark D Segal. Mark pointed out to me that:

  • That image would make a great 30"x45" print
  • Those artefacts I observed would be visible with a loupe in that print
  • But those artefacts would not be visible to then naked eye

So, I repeated the experiment, just using a small crop. My print would be 49" on the long size (if I recall this correctly). Looking close (8" or so) with the naked I could see that foretold artefacts, but I am near sighted. Moving away from the print the jaggies were no longer visible. With my progressive glasses I could not observe those jaggies at any distance.

So, what I have observed that small differences in actual pixels images or small artefacts are not very visible in prints. The details are transferred but a loupe may be needed to observe them.

What I could see in a few previous experiments, there was very little difference in prints made from 24MP and 39 MP at A2-size. But I have been told by an experienced printer that there is a clear and observable benefit of 36 MP to 16MP (or even 24P?) at A2-size when printing on glossy paper. I have also learned that we can learn to see certain differences. First you don't see it than you see it.

I guess, if we have enough pixels that are good enough we can print large and reach near optimum. Adding more pixels may not yield significant benefits.

Close scrutiny on screen corresponds to wall size prints. If we assume 100PPI on screen, it would correspond to something like a 2.5 m wide print from the IQ-180.

So, my take from that test is that we now have great tools at affordable prices and I am the last one to complain.

Best regards
Erik




Interesting comparison. I've owned the IQ180 (but not the 35LS) and now own the 645Z (but not the 28-45).

To my eyes, in the posted samples, the Phase files do look sharper and hence better if only resolution is compared.

Several points need to be understood in a comparison of this sort, IMHO.

1. Lens: More than the camera, I believe the lens is the key, especially if the sensors are both equally capable. I wonder how the Pentax would have performed say with the DFA 55 or DFA 90, both being modern prime lenses well suited to the digital medium, or if the two systems were compared with zooms of a similar range.

2. Ultimate objective: I may be wrong, but the final resting place of any image must be a print, whether on paper or aluminum or whatever. I doubt we are all happy to just have them sit on a hard drive or on a webserver. In the latter instance, nobody is going to look at the right lower corner at 100% etc. Hence the comparison is useless unless the final destination is taken into account. If it is a print, as I think it would be, then too, the differences at the 'usual' size would be minimal, as was shown so long ago by Michael Reichmann.

When I bought my Phase IQ180 I was told by all the enthusiasts present that the difference in print quality between Phase and a Canon DSLR would be visible at '8X10' size, a blatant untruth.

Having printed large (over 24X36) with Phase 180, Canon 1DX and now Pentax 645Z, I can tell you that unless you are 3 inches from the print or using a loupe, the difference is not noticeable at all at anything smaller than 20X30 and above that, the Pentax and Phase files are absolutely indistinguishable!

So a lot depends upon what you want to do with the images you shoot. Granted, you can 'crop into' a larger resolution file with greater ease but that is hardly the purpose of shooting with a high resolution camera to begin with.

3. Cost: This is the big issue I think with the OP as it was with me. I discovered that the value for me was not there, given my style of shooting and there were several major limitations to boot. However, this is a very subjective matter and for many the value is in the joy they get out of using the system and nobody can argue with that.

BTW, I also own the A7RII now and the superb Batis lenses and as I've said repeatedly, the combination of the Sony and the Batis 25 is just about the best IQ for the price and heft.
 
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Pradeep

Member
Hi,

I guess the posting says a couple of things:

  • The Pentax 645Z performs on par with IQ-180 within it's resolution limits.
  • The zoom lens seems to be performing very well (which is the reason to check a corner)
  • So you can make significant savings if you don't need the 80 MP

What I would add is that with f/14 there is significant diffraction in the play. The Pentax would have a larger DoF (due to crop factor / shorter lens), so it could be shot at f/11 thus having somewhat less diffraction. On the other hand, diffraction can be corrected for by sharpening and no resolution will be lost at f/14.

I also agree mostly what you say about print sizes. I had a small discussion about demosaic artefacts I have observed in Lightroom on one of my Sony A7rII images with Mark D Segal. Mark pointed out to me that:

  • That image would make a great 30"x45" print
  • Those artefacts I observed would be visible with a loupe in that print
  • But those artefacts would not be visible to then naked eye

So, I repeated the experiment, just using a small crop. My print would be 49" on the long size (if I recall this correctly). Looking close (8" or so) with the naked I could see that foretold artefacts, but I am near sighted. Moving away from the print the jaggies were no longer visible. With my progressive glasses I could not observe those jaggies at any distance.

So, what I have observed that small differences in actual pixels images or small artefacts are not very visible in prints. The details are transferred but a loupe may be needed to observe them.

What I could see in a few previous experiments, there was very little difference in prints made from 24MP and 39 MP at A2-size. But I have been told by an experienced printer that there is a clear and observable benefit of 36 MP to 16MP (or even 24P?) at A2-size when printing on glossy paper. I have also learned that we can learn to see certain differences. First you don't see it than you see it.

I guess, if we have enough pixels that are good enough we can print large and reach near optimum. Adding more pixels may not yield significant benefits.

Close scrutiny on screen corresponds to wall size prints. If we assume 100PPI on screen, it would correspond to something like a 2.5 m wide print from the IQ-180.

So, my take from that test is that we now have great tools at affordable prices and I am the last one to complain.

Best regards
Erik
Erik, I think print size really is the final determinant, as is of course the paper type.

Having said that, viewing on a monitor is a variable phenomenon and also depends upon what the resolution the monitor is set at. So 100ppi may be different on a 4K vs a standard HD monitor, at least that is my understanding.

I have a B&W image of the NYC skyline at night taken with the IQ180. It has great detail obviously, being a very high res file. I printed this on my Epson 9900 on BC vibrant metallic and BC Elegance velvet at 30 X 40. The matte print had more detail in it but I had to view it from 6-8 inches to notice the difference. So it is not true (at least from my own observations) that a glossy print will necessarily bring out the best detail.

The smaller the print, the closer the viewing distance, people can hold an 8X10 to their nose. I have a 44 X 72 print from my Canon 1D4 that hangs in my basement. At 'normal' viewing distance of say 4-6 ft it looks fine. Obviously as you come closer you see the fuzziness.

What is true is that we have so many options at all price points and you just pick what suits your style and budget. I think many of us (myself for sure) make the mistake of thinking 'resolution' without thinking what one would end up doing with the image in the end.
 

MrSmith

Member
No doubt the 645z is appealing. I just noticed it is now 7K at BH Photo. I did not realize the body had come down from 8.4K.

Paul
Still $1k more expensive than a phase one xf, it doesn't even come withe an elk leather strap like the phase one.
I guess you do get a 50mpixel sensor thrown in with the Pentax though.
 

tcdeveau

Well-known member
The 645z price at B&H just went back up to 8.5K.
I spoke to a B&H representative about this over the weekend and he said that there was "no indication the price drop was temporary" in his system, but it looks like it was indeed a temp price drop for PPE .
 

Paul2660

Well-known member
I know it was valid as I had one in my cart ready to checkout then I had a sane moment and backed out. Just can't afford to switch from Phase One as I have a bit too much invested. But it was really tempting.

Paul C
 

tcdeveau

Well-known member
I know it was valid as I had one in my cart ready to checkout then I had a sane moment and backed out. Just can't afford to switch from Phase One as I have a bit too much invested. But it was really tempting.

Paul C
Oh it was definitely valid. I was thinking about getting one myself. I just asked B&H if it was a temporary sale price for the PPE show or a permanent price drop to see how much time I had to pull the trigger. They said they thought the price drop would stick around for awhile. However it appeared to be a weekend sale only.
 

turtle

New member
I see the IQ180 having a hair better detail when downsized, but suspect that gap would open up a bit with the 645Z uprezzed to 80MP. The big issue I suppose is whether 50MP is the point at which you don't need more resolution for your uses. For some this will be 'yes' and others 'hell, no'. If yes, one reaps the many benefits of the 645Z and its amazing sensor. For someone routinely making 60" prints and selling them for $5K each, I could see why 80MP would retain its allure.

Regarding the 28-45mm, it is indeed amazing. At the apertures I need to use it (landscapes) it performs better than any zoom lens I have ever used and better than most of the primes I have ever owned. It is staggering and would say its in the same ballpark as using Leica M (or Zeiss ZM) wide angle primes on a digital M at landscape apertures. The edges and corners are astonishing. It also will perform a touch better at f8-f9 than f13, but that said, the difference is not that great. I see it as a slight reduction in 'bite' - perfect edge contrast softens a bit - but the results are still incredible. I think this lens will be able to handle more resolution so a good bet for the next 645 model too.

I am awaiting the new 45-85 and 80-160mm lenses from Pentax. If they are anything like the 28-45, we're in for a treat.
 

Dan Santoso

New member
FF Pentax is coming next year with new tech and new IQ I hope.

While the IQ 1 to 2, and 3 only has improvement in high iso and new features that is not connected to IQ. Studio uses will not give you difference quality.

The XF is out now i want to see the next generation of the back hopefully by next year. Is it about time Phase one up their game? I would love to have anti shake in the back:thumbup:


I see the IQ180 having a hair better detail when downsized, but suspect that gap would open up a bit with the 645Z uprezzed to 80MP. The big issue I suppose is whether 50MP is the point at which you don't need more resolution for your uses. For some this will be 'yes' and others 'hell, no'. If yes, one reaps the many benefits of the 645Z and its amazing sensor. For someone routinely making 60" prints and selling them for $5K each, I could see why 80MP would retain its allure.

Regarding the 28-45mm, it is indeed amazing. At the apertures I need to use it (landscapes) it performs better than any zoom lens I have ever used and better than most of the primes I have ever owned. It is staggering and would say its in the same ballpark as using Leica M (or Zeiss ZM) wide angle primes on a digital M at landscape apertures. The edges and corners are astonishing. It also will perform a touch better at f8-f9 than f13, but that said, the difference is not that great. I see it as a slight reduction in 'bite' - perfect edge contrast softens a bit - but the results are still incredible. I think this lens will be able to handle more resolution so a good bet for the next 645 model too.

I am awaiting the new 45-85 and 80-160mm lenses from Pentax. If they are anything like the 28-45, we're in for a treat.
 

scho

Well-known member
I spoke to a B&H representative about this over the weekend and he said that there was "no indication the price drop was temporary" in his system, but it looks like it was indeed a temp price drop for PPE .
Back down to 7K at B&H.
 

Pradeep

Member
FF Pentax is coming next year with new tech and new IQ I hope.

While the IQ 1 to 2, and 3 only has improvement in high iso and new features that is not connected to IQ. Studio uses will not give you difference quality.

The XF is out now i want to see the next generation of the back hopefully by next year. Is it about time Phase one up their game? I would love to have anti shake in the back:thumbup:
I doubt very much Phase or anyone else will be coming up with a FF 645 CMOS sensor. It will not offer that much more quality than the cropped sensors in the Pentax, Hassy and Phase backs and will probably cost too much to make. The profits realized would be minimal and if I was the CEO of any of these companies I would not invest in such a venture. Better to maximize qualities of the existing sensor and cameras the way Sony has shown with the humble 35mm model. There is still valuable real estate in the MF sensor that can be better utilized.

The need of the hour, IMHO is to make a smaller body capable of utilizing the cropped 645 sensor to its fullest and allowing 3rd party lenses to be used with adapters. I am sure Pentax can do it and probably will. If they can then sell it at the current $6-8K price point, it would be a winner.
 

jerome_m

Member
I doubt very much Phase or anyone else will be coming up with a FF 645 CMOS sensor. It will not offer that much more quality than the cropped sensors in the Pentax, Hassy and Phase backs and will probably cost too much to make. The profits realized would be minimal and if I was the CEO of any of these companies I would not invest in such a venture.
On the other hand, maybe the CEO of these companies think that there are enough customers ready to pay a premium for a bigger sensor to justify these costs.
 
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