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03-26-2015, 05:39 AM   #1
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Pentax 645 lens resolving power

My question concerns the 645Z camera vs. FF cameras such as the D810 and the forthcoming 5DS and the currently available lenses for both systems.

I’m curious to hear what digital shooters have to say on the following hypothetical situation. If money weren’t an issue, which of the two systems would you go for:

- Pentax 645Z with current lens lineup (25mm, 28-45mm, 55mm, 90mm) designed for it
OR
- Nikon D810 or Canon 5DS with the Zeiss Otus lenses, which are considered by many to be the best performing lenses in the world as far as resolving power is concerned. AND my question concerns only lens resolving power - not the auto vs. manual question in other words.

D810 or 5DS with the Zeiss Otus lenses:
Only the Otus lenses are said to resolve more than 35MP at the moment... which begs the question how many mega pixels the lenses for the 645Z would resolve if they were tested by dxomark…

Lloyd Chambers (diglloyd) has run a number tests and has come to the conclusion that only the 645 90mm macro comes close to approaching the Otus line. What he says about the 645 55mm is quite disparaging…

The question is an old one: resolving power of outstanding lenses (Otus) on FF, or the 645Z's outstanding sensor coupled with average or slightly above average Pentax lenses (aside from the 90mm macro, which is indeed above average and the best 645 lens).

Even older question: investing in glass or camera body? Most photographers say glass… therefore, the Otus + D810 or 5DS would seem to be the wisest choice moneywise given that FF 50MP cameras are here and that they may indeed be able to resolve over 45MP.

So why would someone invest in the 645Z system in other words given that there are more performing lenses out there and that FF 50MP cameras are just around the corner?

Playing devil’s advocate here …

03-26-2015, 07:41 AM   #2
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Test charts aside, I feel like all of my lenses can resolve the sensor at least by f/5.6

While the Otus is an amazing performer, I think that wide-open sharpness is a "thing" that I outgrew by the time I made my move to MF, if you want sharpness, you also need the depth of field to see it.

Shooting at f/1.4 with the Otus will give you a very sharp 1% of the image field if that's your thing.
03-26-2015, 08:02 AM   #3
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Matt granger did a side by side on youtube comparing an otus and d810 vs a 645z. He did say the otus was sharper by a smidge...but its only one focal length. And even if they add other focal lengths, that lens is still mf and 4k dollars. This doesnt even take into account the iso performance
03-26-2015, 08:02 AM - 1 Like   #4
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QuoteOriginally posted by BrunoL Quote
My question concerns the 645Z camera vs. FF cameras such as the D810 and the forthcoming 5DS and the currently available lenses for both systems.

I’m curious to hear what digital shooters have to say on the following hypothetical situation. If money weren’t an issue, which of the two systems would you go for:

- Pentax 645Z with current lens lineup (25mm, 28-45mm, 55mm, 90mm) designed for it
OR
- Nikon D810 or Canon 5DS with the Zeiss Otus lenses, which are considered by many to be the best performing lenses in the world as far as resolving power is concerned. AND my question concerns only lens resolving power - not the auto vs. manual question in other words.

D810 or 5DS with the Zeiss Otus lenses:
Only the Otus lenses are said to resolve more than 35MP at the moment... which begs the question how many mega pixels the lenses for the 645Z would resolve if they were tested by dxomark…

Lloyd Chambers (diglloyd) has run a number tests and has come to the conclusion that only the 645 90mm macro comes close to approaching the Otus line. What he says about the 645 55mm is quite disparaging…

The question is an old one: resolving power of outstanding lenses (Otus) on FF, or the 645Z's outstanding sensor coupled with average or slightly above average Pentax lenses (aside from the 90mm macro, which is indeed above average and the best 645 lens).

Even older question: investing in glass or camera body? Most photographers say glass… therefore, the Otus + D810 or 5DS would seem to be the wisest choice moneywise given that FF 50MP cameras are here and that they may indeed be able to resolve over 45MP.

So why would someone invest in the 645Z system in other words given that there are more performing lenses out there and that FF 50MP cameras are just around the corner?

Playing devil’s advocate here …
Well, personally I think this whole thing is a ridiculous comparison, and have thought so before this post. Why? Because the Otus "line" consists of exactly 2 lenses. Now, If these are the only 2 FL's you use, and all you care about is resolution at base iso (and nothing else!), and you are starting fresh with no other cameras or lenses, then the choice seems clear to me: Nikon 810 and the 2 Otus lenses.

If, on the other hand, you have other considerations, such as shooting at higher iso's, DR, general attributes of MF vs. FF, and for me, most importantly (although the others are real important to me), shooting across a range of FL's (The 2 Otus lenses are far from my favorite FL's), then I also think the choice is clear: the Z and a range of lenses.

BTW, another thing I find issue with is the denigration of the Pentax 645 legacy lenses. That's another whole story. Let's just say I don't buy it---and that doesn't even count the 67 lenses.

With trade-ins, and because I had several 645 lenses already, I've been able to put together a true system based around the Z, including new flashes and wireless triggers, new bag, 2 new lightsands and a new, more robust monopod and head, quick release plates, and a few other accessories, a total of 12 lenses---and the total cost for all of it has been below $10K.

I've been shooting seriously since 1979, 35mm, MF, and LF, digital starting in 2001, and right before the Z I had upgraded to the A7R. I haven't tapped out on the potential of that camera yet, but I can sense that the full potential is somewhere over "in the next valley or ridge". But I haven't even remotely begun to touch all the goodness in this Z system, still adjusting to it, and I feel like the limits of its potential to me are somewhere over at the opposite end of the continent, comparatively and figuratively speaking.

---------- Post added 03-26-15 at 11:04 AM ----------

QuoteOriginally posted by y0chang Quote
Matt granger did a side by side on youtube comparing an otus and d810 vs a 645z. He did say the otus was sharper by a smidge...but its only one focal length. And even if they add other focal lengths, that lens is still mf and 4k dollars. This doesnt even take into account the iso performance
And IIRC, I thought there were some problems with that comparison when you looked closely, under the blanket so to speak.

03-26-2015, 08:25 AM   #5
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Grainger shot the 645 55/2.8 wide open, and the 1.4 otus stopped down to f2.8. If he wanted to compare sharpness he should have shot both systems at f5.6, what he perceived as superior sharpness was greater dof, that's all.
03-26-2015, 08:42 AM   #6
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I also want to add that the Otus line, with our current foreseeable level of technology, is the pinnacle of 35mm SLR lens design. The outrageous size and weight, manual-only operation, and high cost, all to push the limits of what can be done with the optics.
Comparison wise, Pentax have yet to stretch their legs, the 55mm & 25mm lenses I find to be only the transitional phase to digital-optimized glass, while the 90mm and 28-45mm are more indicative of what can be done on the format. With the coming 45-85mm 4.5 SR and 80-160mm 4.5 SR the system is looking to have a very strong zoom lineup.

Pentax also has the better prospect of releasing leaf shutter lenses under pressure from it's users, if they made something like Leica's 100mm f/2 but with a leaf shutter, the Pentax system would be back-ordered forever.

QuoteOriginally posted by Stavri Quote
Grainger shot the 645 55/2.8 wide open, and the 1.4 otus stopped down to f2.8. If he wanted to compare sharpness he should have shot both systems at f5.6, what he perceived as superior sharpness was greater dof, that's all.
If you want to equalize aperture across 35mm and 33x44, add one and a third stop to the aperture of the 35mm system; that is f/2.8 on the 645Z is like f/1.8 on the D810, and f/4.5 is like f/2.8, etc.
03-26-2015, 09:31 AM   #7
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I've shot a lot with fast manual focus glass (58mm 1.2, 50mm 0.95, 200mm f2) and I can't help but think that the image quality of the Otus is hindered by the MF setup. Supreme quality @ 1.4 is all well and good, but missing critical focus makes it moot. Especially on DSLR's with non-removable focus screens optimized for focusing at 2.8
03-26-2015, 09:51 AM   #8
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QuoteOriginally posted by Frink Quote
I've shot a lot with fast manual focus glass (58mm 1.2, 50mm 0.95, 200mm f2) and I can't help but think that the image quality of the Otus is hindered by the MF setup. Supreme quality @ 1.4 is all well and good, but missing critical focus makes it moot.
I've actually not seen that many f1.4 shots at an 85mm FL that I thought were all that marvelous, just sayin'. Not a huge fan of the "this eye's in focus, that one's not" look. But personally I always felt that fast glass was partly as fast as it was to optimize performance closer to wide open, not actually at it. But sometimes I know that's not true.
QuoteQuote:
Especially on DSLR's with non-removable focus screens optimized for focusing at 2.8
oooo, and a little insider baseball thrown in! Interesting point if true. Which screen for the 810 is optimized for focus @ f1.4?

03-26-2015, 10:21 AM   #9
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This is a very important thread because it proves the need and interest for OTUS for medium format. What I wouldn't give for an OTUS in pentax 645 mount !!!!
03-26-2015, 02:14 PM - 1 Like   #10
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Hi all,
had the Z for 2 weeks now with 35A(+)75FA(++)120FA(-)and Zeiss150(++).
lots of pros and a couple of cons, but comparing it with my D810 just convinced me to keep it.
I actually used the same lens on both of them, which I've not seen anybody do so far, correct me if i'm wrong.
so my sharpest lens is the 150f4 Hasselblad Sonnar T✶.
used with the respective adapters and focussed manually in LV, it clearly shows that the 645Z sensor outresolves the Nikon.
sadly the LV/screen on the 645 is a lot worse than the Nikon. and don't get me started on the ridiculous autogain issue...
but the viewfinder is definitely better than the 810's.
It is pretty hard focussing manually through the viewfinder with a 150 anyway.
so would I be getting an Otus ?
I don't think so, since I have to rely on AF when I am shooting people and the 75/2.8Z combo gives me lot of joy for that.
and those sensors without tripod? start at 1/800 to be impressed.
the other thing is weight/handling/balance.
just put the Nikon on a tripod with the Otus and see and feel (and curse) for yourself...
just my 50c

cheers
Stephan
03-26-2015, 10:06 PM   #11
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Firstly, in my opinion the only lenses truly designed for the Z system are the DFA 90mm and the DA 28-45. They are both superb.

The others, while ok, were made with the legacy systems in mind and not with a no-compromise approach like the 2 above.

The advantage in my view of the Otus lenses is that they are so highly corrected wide open that live view focussing is a breeze due to the fact that there is no aberrations and contrast is near perfect wide open. The pentax lenses do not have this. It makes exact critical manual focussing much easier.

It also comes down to what you like. I will never own a Nikon unless they make them look and feel like a Canon, I just don't like them. Doesn't mean they are crap though.

When I first picked up a 645D I just knew I was going to own one, no question. Now that I have the Z, I am very happy and do not lust for a D810 at all.

I can't wait for the new 80-160 or 90-180 to come out then I am set!
04-03-2015, 12:13 AM   #12
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just my opinion and I can take the heat.. a lot is being said about lenses made for digital cameras, but I think it's overblown. when the 645d came out it was tested with 645 film lenses and the opinions were WOW. the new lenses may be a little better, but after spending $8500.00, $12,000.00 for 3 lenses may be toooo much for their wallets. i'm using the 35-400mm lenses and they work great for me.i even use 2 67 lenses, I also use the 1.4 and the 2.0 tc's and get "RAZOR" sharp images. and i'm just an amateur who makes the most of what he has. also i'm not a nit-picker.
04-03-2015, 01:04 PM   #13
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Look 35mm released large aperture lenses to mimic the look of MF. Why don't you skip the mimicking, and just shoot MF. If you already have a FF camera, and are shooting an Otus, more power to you. But to compare MF to 35mm is like comparing a sports car to a pickup truck and comparing trunk sizes. Two different cars, two different purposes.
04-03-2015, 01:38 PM   #14
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On top of what I said earlier, I still believe that if you wanted a lightweight 2 lens kit for the 645d/z, I would not hesitate with the A35 and FA120 and be done. An excellent set and both older lenses.
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