The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Pentax 645Z vs A7RII IQ and bang for the buck

I assisted a lot of fashion photographers and their preferred brand was Pentax. Despite being temperamental and often having shutter problems requiring as many as 2 back up bodies for a shoot (at least in the case of the Pentax 67) the lenses produced the most beautiful skin tones and bokeh. Is the field curvature of the 55mm a common trait of Pentax lenses and therefore an explanation for Pentax popularity amongst fashion photographers???
No, it's just this lens, at least by what I know. The 55mm wouldn't be notorious for it's field curvature if it were a common trait among Pentax lenses. I rarely shoot images like the one above, so it's not a big problem. For "3D" subjects like this one it's even advantageous: https://dl.dropboxusercontent.com/u/41183616/_IMG2170.jpg

What I do find as a common trait is a high level of LoCA, that is magenta/green fringing of detail in front of or behind the plane of focus, all of the Pentax lenses I've used have it, even when stopped down a little. The 150mm is the worst offender (wide-open), but at f/8 it's also the sharpest lens I've ever used, with an absolutely flat field; because of this I use it for art reproduction whenever possible.
 

tsjanik

Well-known member
Given your applications you might consider using the Pentax 67 55mm (last version, widely regarded as one of the best 67 lenses) along with a Zoerk shift adapter.

http://www.zoerk.com/pages/p_pshift.htm

I have no experience with the new DFA 55mm, but the old 55mm A and the 67 55mm have flat fields. Most copies of the 120mm are superb. The 28-45, 75 and 45-85 are also very good in that order. I have no experience with the 90mm or 25mm.

Tom
 

jerome_m

Member
Do you wish to contribute something RELEVANT to this thread Jerome
You are the one who hijacked this thread and started to post about Hasselblad lenses, which are neither relevant to the 645z nor relevant to the A7RII. I just tried to correct the most obvious inaccuracies without hijacking the thread.

Now you asked the question whether I can contribute something relevant. To this specific thread, which is about the 645z and the A7RII, probably not. I don't have these cameras. About Hasselblad lenses, I contributed this and that, in lula at the time. You'll find the same test pictures in that other forum, which will still be accessible for free after lula will hide behind a paywall in 7 days and also this. Is that relevant? I don't know, you tell me.
 

justalexander

New member
You are the one who hijacked this thread and started to post about Hasselblad lenses, which are neither relevant to the 645z nor relevant to the A7RII. I just tried to correct the most obvious inaccuracies without hijacking the thread.

Now you asked the question whether I can contribute something relevant. To this specific thread, which is about the 645z and the A7RII, probably not. I don't have these cameras. About Hasselblad lenses, I contributed this and that, in lula at the time. You'll find the same test pictures in that other forum, which will still be accessible for free after lula will hide behind a paywall in 7 days and also this. Is that relevant? I don't know, you tell me.

I gave my opinion based on the personal experience I had reviewed based on the equipment I had been using. This would help readers understand the differences between the different formats and what it was in particular I was hoping to find in the 645Z. All legitimate. You post useless unsubstantiated comments that are just plain rude. You didnt even have the decency to divulge what camera system you were using!

A polite reply might have gone something like this.... 'Well I've been using the H4D50 for X years and I'm curious to know WHY you feel the 50MP sensor isn't up to scratch." And you might have done it using a private message so as not to littler this thread with irrelevant conversation. So if you cant contribute anything relevant to the thread why bother wasting everyones time???
 

Bryan Stephens

Workshop Member
Hasselblad has had a 200 mpix camera for some years now (multishot) and the people using it do not complain that the lenses are not fit to that resolution.
Just my two cents. The 200ms is nothing more than the 50c sensor that combines several images internally (if you so choose that setting), or you can shoot it the same way (single shot) that the 50c back works. It is not a 200mp sensor. There is a world of difference. If the lenses work on the 50c then they will work on the 200ms
 

Bryan Stephens

Workshop Member
You are the one who hijacked this thread and started to post about Hasselblad lenses, which are neither relevant to the 645z nor relevant to the A7RII. I just tried to correct the most obvious inaccuracies without hijacking the thread
Actually you can use the Hassy V lenses on the Pentax 645z and the Sony a7rII with an adapter so these could be part of the dicussion, but I believe there was a separate thread dedicated to that (at least with regards to the Pentax system that I know of).
 

jerome_m

Member
Just my two cents. The 200ms is nothing more than the 50c sensor that combines several images internally (if you so choose that setting), or you can shoot it the same way (single shot) that the 50c back works. It is not a 200mp sensor. There is a world of difference. If the lenses work on the 50c then they will work on the 200ms
x megapixels emulated from multishot are just as taxing on the lenses as x megapixels natively captured.
 

jerome_m

Member
I gave my opinion based on the personal experience I had reviewed based on the equipment I had been using. This would help readers understand the differences between the different formats and what it was in particular I was hoping to find in the 645Z. All legitimate. You post useless unsubstantiated comments that are just plain rude. You didnt even have the decency to divulge what camera system you were using!

A polite reply might have gone something like this.... 'Well I've been using the H4D50 for X years and I'm curious to know WHY you feel the 50MP sensor isn't up to scratch." And you might have done it using a private message so as not to littler this thread with irrelevant conversation. So if you cant contribute anything relevant to the thread why bother wasting everyones time???
What I see is that you posted this bizarre idea that H lenses would not be fit for a 50 mpix sensor. You also posted the incorrect statement that H lenses had never been upgraded since 2002 as "evidence". I though it beneficial to the thread to put these statements in doubt.

Now, if you had bothered to clic the links I gave in my previous message, you would have found supporting evidence to my statement about the H lenses, as I have personally tested each H lens between 24mm and 100mm and posted the results.

You are also telling us that you photograph architecture. If this is your line of work, I don't understand why you even consider changing brands since the distortion correction of Phocus is a unique feature quite essential to that particular line of work, as you explained yourself. Maybe the reason you consider changing brands is because of that bizarre idea that H lenses would be too poor for 50 mpix? If such is the case, maybe you would benefit from testing these lenses again. OTOH, if you think that my posting are just wasting your time, simply ignore them and I won't have to post anything more to that thread myself.
 

Bryan Stephens

Workshop Member
x megapixels emulated from multishot are just as taxing on the lenses as x megapixels natively captured.
If I am not mistaken, it is the SAME sensor as in the 50c, so if the lenses work on the H5D-50c they will work on the 200ms.

With regards to your other post, I have shot the h4D-50 and used the H lenses and they seemed to work fine on that back, at least in my opinion.
 

jerome_m

Member
If I am not mistaken, it is the SAME sensor as in the 50c, so if the lenses work on the H5D-50c they will work on the 200ms.

It is the same sensor, but the multishot process emulates a higher resolution sensor and increases the sample frequency. One will see better the limitations of the lenses.
 

Bryan Stephens

Workshop Member
It is the same sensor, but the multishot process emulates a higher resolution sensor and increases the sample frequency. One will see better the limitations of the lenses.
Yes and no. It emulates the output of a higher res sensor, but the input is identical to the 50c sensor in single shot mode. It takes multiple single shots (I believe between 2 and 6) and combines them, so it really is not the same as if it were a true 200mp sensor. If it did behave in that manner, you would REALLY need some impressive glass to get optimal results, any any shortfall would be magnified.

I think even the impressive 60XL or the 40HR would show any possible flaws at that pixel level
 

jerome_m

Member
If it did behave in that manner, you would REALLY need some impressive glass to get optimal results, any any shortfall would be magnified.

It does behave in that manner. I don't really want to discuss the underlying reason, but this is a consequence of the transfer functions of the lens and sensor being linear. If you had stepping motors of infinite precision, you could actually completely characterise a lens with a single pixel moved around.

As to the glass being impressive, not that much. Multishot backs of that sort increase the resolution by a factor of two, but the MTF of the lenses will not suddenly go to zero when one samples twice as much. One sees the defects of a given lens more clearly, but the lenses do not suddenly turn to mush just because one has 4 times more pixels, just as good lenses from the film era did not suddenly turn to mush when 24x36 SLRs went from 6 mpix to 24 mpix.
 
Top