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04-06-2016, 11:27 AM   #31
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QuoteOriginally posted by osv Quote
it's an astounding example of minimal field curvature, which results in a flat focus field: Tim Ashley Photography | Field Curvature - a Layman's Guide (or How to Focus a 'Tricky' Lens)

yes, the korean 35/1.4 lenses also have a wavy field curvature issue, seen on the right side, but that's not what i'm referring to... i'm assuming zero moustache distortion, i'm talking about comparing focusing between the edges and the centers, which varies greatly with lens design.
I'm presuming this is the Art series Sigma? I find it hilarious then that first you cherrypicked a very new lens that has a reputation for a very flat field, then post an "astounding" example from what clearly is a bum sample that is a smeary mess on the left and does show obvious distortion, presumably due to alignment issues.

QuoteOriginally posted by osv Quote

we are on the same page here, we did it the same way... yes it's a small advantage, however that's all that's needed for foreground objects... in theory, if we are working with equal dof/fl on both platforms, how much of a difference can there really be? it's the entire basis of equivalence.
There you go, moving the goalposts again. We are liteally talking a couple of feet at the f/16-f/22 range where landscapes are typically taken. With all the inherent advantages of the larger sensor still remaining.


QuoteOriginally posted by osv Quote
nothing that i did is about dof anyway, it was always strictly about field curvature and lens design.
Funny, you injected yourself into a discussion about DOF with that image, in direct response to my point that the vast majority of the time landscape photographers will be using small apertures to maximize DOF over the whole image, a scenario where your ill thought-out tangent about flat fields is irrelevant.


QuoteOriginally posted by osv Quote
there is no diffraction advantage either way here, and there is no real dof advantage with either platform... same exact scenario with crop vs. ff.
At the edge of diffraction maybe, but utter BS if you are 3 stops past the diffraction limit.

QuoteOriginally posted by osv Quote
what that refers to is how pixel density affects diffraction visibility, and there are two sides to that argument, read the link i posted.
I did read it, and as that very article states, his point is for equivalent apparent DOF at different sensor sizes. Letting alone the fact that we are talking about two different lenses with different focal lengths, his point is that at extremely small apertures, the effects of diffraction converge asymptotically. However, for sensors of different sizes (and by extension pixel densities for equivalent overall resolution), the diffraction limit is lower for smaller sensors, and larger sensors can be stopped down further before diffraction blur is perceived as stronf.

QuoteOriginally posted by osv Quote
to sum it up, pixel density has it's advantages even when the dof/diffraction is equal, because it still retains more resolution.
I presume you are seizing on this quote: "All else equal, more pixels will always resolve more detail, regardless of other sources of blur, including diffraction."
But you missed out on a couple of importnat things. First, he is specifically talking about 2 systems with identically sized sensors using an identical lens. And he is talking strictly about maximum overall detail, NOT about signal to noise ratio or dynamic rnage, both of which will be significantly degraded as the pixels get smaller, and to a greater relative degree than the resolution will increase, since not only will they gather less light due to size, but proporitonally more of each photosite is devoted toward support electronics, meaning even more photons are sacrificed for each pixel gathered.


QuoteOriginally posted by osv Quote
i'm not moving anything, this is reality because there are no lens choices with mf, if your lens has significant field curvature, tough luck, you are stuck with it.
Sigh, moving the goalposts again. So now it's about lens choice? There is exactly one lens produced with the field characteristics that the ART (when you have a decent sample) has. The ART. And it's much newer and more expensive than the equivalent FA lens I referenced! Leaving aside the fact that there are MANY lenses adaptable to the 645 system, including Hassys, Zeisses, and others with varying degrees of field curvature, it also stands to reason that should Pentax actually release a FF 645Z, that more DFA primes optimized for the larger sensor will be in close tow.

QuoteOriginally posted by osv Quote
that's the entire point of everything that i said, mf is at a huge disadvantage due to no lens choices.
Your entire, cherry-picked, tortured point that focuses on one variable in a very narrow set of circumstances with little relevance to landscape photographers and fails to even consider (or rather activelyignores) the many very real advantages that shooting MF brings.

04-06-2016, 01:20 PM   #32
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QuoteOriginally posted by dcshooter Quote
I'm presuming this is the Art series Sigma?
no, it's one of the korean 35/1.4 junk lenses.

QuoteOriginally posted by dcshooter Quote
There you go, moving the goalposts again. We are liteally talking a couple of feet at the f/16-f/22 range where landscapes are typically taken.
no, it's foolish to shoot ff landscape shots at f/16-f/22, because of diffraction losses... for example, this m28/3.5 ooc jpeg shot, taken at f/8 or possibly f/10, are you really going to sit there and claim that it should have been shot at f/16-f/22? blow it up to 100%, and tell us what exactly would be gained by taking this pic at f/16-f/22:

https://www.dropbox.com/s/86ch2xumwhq060r/DSC01364smcm283point5f8.JPG

QuoteOriginally posted by dcshooter Quote
Funny, you injected yourself into a discussion about DOF with that image,
this was never a discussion about dof, read the thread title: "645z owners: will you switch to sony 75mp a7riii"

i never claimed anything about dof platform comparisons, because it doesn't matter; that was your tangent entirely, my point was field curvature and lens design advantages at wider apertures.

QuoteOriginally posted by dcshooter Quote
in direct response to my point that the vast majority of the time landscape photographers will be using small apertures to maximize DOF over the whole image, a scenario where your ill thought-out tangent about flat fields is irrelevant.
no, whwang for instance was very clear, he said the same thing that i did: "You may say this is not fair, why we have to compare two different F-ratio? This is exactly what the lens company try to achieve. Better image quality under larger aperture. IF a 35mm FF lens can be used at a larger aperture, everything you said will be canceled out."

i'm not sure why you keep insisting that landscape photos must always be taken at diffraction-crippled apertures

QuoteOriginally posted by dcshooter Quote
iI presume you are seizing on this quote: "All else equal, more pixels will always resolve more detail, regardless of other sources of blur, including diffraction."
But you missed out on a couple of importnat things. First, he is specifically talking about 2 systems with identically sized sensors using an identical lens.
only to illustrate the effects of pixel density, remember that it's an article on equivalence, the effects of pixel density are not relevant to sensor size.

everything that he said there about higher pixel density is verifiable with the Diffraction Limited Aperture Calculator Digital Camera Diffraction – Resolution, Color & Micro-Contrast

raise the pixel density on any given sensor size, and watch what happens.
04-07-2016, 01:25 AM   #33
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Take a chill pill fellows.........

I feel that I would have to buy into the Otus line and a D810 to get better than what I have on my 645z, but even then I might prefer the MF image over the 35mm image.

Sure the A7Rii and future bodies might be good, but really 80mp in a35mm sensor, tech had better come a long long way from where it is now if that is to be any good at all. OSV you would want to have some serious lenses and shot discipline to get the best out of that and I think that only the Otus line would be up to the task. Couple it with a small A7 body, no thanks.
04-07-2016, 02:12 AM - 1 Like   #34
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QuoteOriginally posted by osv Quote
no, it's one of the korean 35/1.4 junk lenses.



no, it's foolish to shoot ff landscape shots at f/16-f/22, because of diffraction losses... for example, this m28/3.5 ooc jpeg shot, taken at f/8 or possibly f/10, are you really going to sit there and claim that it should have been shot at f/16-f/22? blow it up to 100%, and tell us what exactly would be gained by taking this pic at f/16-f/22:

https://www.dropbox.com/s/86ch2xumwhq060r/DSC01364smcm283point5f8.JPG

.
If you could get your head from the computer screen you would realise there are many reasons for landscape photographers to shoot with small apertures. Blow it up to 100%? You don't understand REAL photography at all, stick to your charts and pixel peeping. A photograph - a real one doesn't stand or fall simply by how it looks at 100%. It's about feel and emotion. One or two of the photographs I have submitted to an international gallery aren't pin sharp at 100% but they were still selected by the gallery curators.

Step away from the gear-head aspects and learn aesthetics. Stop looking at pixel level, you'll go cross-eyed

04-07-2016, 02:22 AM - 1 Like   #35
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QuoteOriginally posted by mikeSF Quote
no thanks. it sounds like a downgrade to me.
^ what he said, plus I have a 100Mp camera at my disposal so the small format Sony A7r shooters can go cram it.
04-07-2016, 03:11 AM - 1 Like   #36
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QuoteOriginally posted by osv Quote
no, it's one of the korean 35/1.4 junk lenses.



no, it's foolish to shoot ff landscape shots at f/16-f/22, because of diffraction losses... for example, this m28/3.5 ooc jpeg shot, taken at f/8 or possibly f/10, are you really going to sit there and claim that it should have been shot at f/16-f/22? blow it up to 100%, and tell us what exactly would be gained by taking this pic at f/16-f/22:

https://www.dropbox.com/s/86ch2xumwhq060r/DSC01364smcm283point5f8.JPG



this was never a discussion about dof, read the thread title: "645z owners: will you switch to sony 75mp a7riii"

i never claimed anything about dof platform comparisons, because it doesn't matter; that was your tangent entirely, my point was field curvature and lens design advantages at wider apertures.



no, whwang for instance was very clear, he said the same thing that i did: "You may say this is not fair, why we have to compare two different F-ratio? This is exactly what the lens company try to achieve. Better image quality under larger aperture. IF a 35mm FF lens can be used at a larger aperture, everything you said will be canceled out."

i'm not sure why you keep insisting that landscape photos must always be taken at diffraction-crippled apertures



only to illustrate the effects of pixel density, remember that it's an article on equivalence, the effects of pixel density are not relevant to sensor size.

everything that he said there about higher pixel density is verifiable with the Diffraction Limited Aperture Calculator Digital Camera Diffraction Resolution, Color & Micro-Contrast

raise the pixel density on any given sensor size, and watch what happens.
I think OSV, that it is clear that many of the folks shooting 645z cameras are doing so for landscape photography -- a place where maximum aperture is not as important as dynamic range. Increasing number of megapixels -- particularly if the dynamic range at base iso drops -- is a significant negative in this context. There are plenty of other ways to add resolution to an image, but few ways to add dynamic range to image that simply isn't there.

Anyway, I just think that bringing up lack of f1.4 or f2 lenses for the 645z is not particularly relevant to the way many of these photographers are using their cameras.
04-07-2016, 03:56 AM - 2 Likes   #37
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The original question, "will you down grade from a 645z"?, does not sound like a question asked by a photographer. Most photographers probably want access to every format. They don't replace one with another. They select what is appropriate for the image being taken.

Trying to replace format size with some kind of MP comparison, if you don't know why that's wrong, not much can be said to help you with that.
04-07-2016, 07:22 AM   #38
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God I hate seeing posts about DoF and math equations in a format debate.

I shoot medium format for many reasons and the quality speaks for itself. I don't need a math formula to tell me what camera and lens combination to use.

Now is a great time to own a 645z because when the 645x comes out you can use it to offset the upgrade cost. There has never been a better time to shoot medium format. The only thing I want from Pentax are more lenses without greatly inflated prices relative to the body.

04-07-2016, 07:38 AM - 1 Like   #39
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QuoteOriginally posted by SeattleDucks Quote
Sony has made clear their intentions to continue ramping up resolution in their fullframe cameras, and that's their stated reason for introducing the new higher resolution G Master lenses. Now a Japan source source (published on the web today) is indicating the upcoming A7RIII will have a 75-80MP sensor, and improved 5-axis IBIS.

For me, I love extremely fine detail capture for landscape images, as I do print large and I do enjoy getting up close to a fine art print and seeing breathtaking detail of beautiful subjects. I've owned a ton of digital cameras in the last decade and the 645Z is the first that has come close to giving me 40x30 prints that have resolution rivaling prints from 600MB drum scans from 4x5 Velvia originals (and of course the 645Z blows the 4x5 transparencies away in dynamic range).

If I were to switch to the upcoming Sony it would be not only for the additional resolution but also the 5-axis IBIS and small packable size/weight, making it an ideal travel camera. Also, the ability to adapt virtually any lens to the Sony is very intriguing, as I'd love to use the excellent Canon 24mm TS-E II, among others.

And for those who don't print huge, note that the very exacting and picky Lloyd Chambers has shown that oversampling with more pixels than you think you will ever need does produce better IQ in even modest size prints, as it reduces any sign of digital artifacts.

It would be an interesting discussion to see if any current owners of the 645Z think they will switch over to this new Sony? Why, or why not? Obviously there is no right or wrong answer here. I'd love to hear your own thoughts.

Cheers,
Ross
Switch? No.
Add to kit? Yep.

I might trade my 645z for a 100 MP version.
04-07-2016, 07:56 AM   #40
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QuoteOriginally posted by normhead Quote
.....Most photographers probably want access to every format. They don't replace one with another. They select what is appropriate for the image being taken.
Trying to replace format size with some kind of MP comparison, if you don't know why that's wrong, not much can be said to help you with that.
That's spot on really. I've just taken delivery of a 645Z to augment my Canon 35mm DSLR's, not replace them.

Bob
04-07-2016, 08:45 AM   #41
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QuoteOriginally posted by rfkiii Quote
Switch? No.
Add to kit? Yep.

I might trade my 645z for a 100 MP version.
+1 from me
04-07-2016, 09:16 AM - 1 Like   #42
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QuoteOriginally posted by SeattleDucks Quote
.....

I didn't realize this was an elitist forum where only those with bountiful supplies of money allotted for new gear were allowed to post...
Sorry, I didn't mean to offend you, or anybody else, with my comments nor did I wish to sound elitist.

Bob
04-07-2016, 09:19 AM   #43
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You asked the question, I didn't.

I notice now you add that you don't have the money for both systems. Put all relevant information in your original post and we won't have these little scuffles. I've always said I won't buy into a new system unless I have a gig that will pay for it. So, I'm hardly elitist.

I'm just pointing out the obvious here.

And, you're getting irritating.

What kind of person, basically bragging on a forum that he has a $15,000 system, calls someone who doesn't own $10,000 in camera gear altogether an elitist? You have it backwards. You've got the elitist $15,000 system, and you ask 40,000 site members who will never face that problem to think about your little conundrum.

I guess you have no sense of how ironic that is.

OK ya, I'm an elitist, I admit it. So sue me.

And there is nothing I can do to stop you from posting... so quit your "poor me, I'm a victim" whining.

Post whatever you want. It's a public forum, I can comment if I choose.



Sheesh.
04-07-2016, 09:25 AM   #44
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QuoteOriginally posted by Rondec Quote
Anyway, I just think that bringing up lack of f1.4 or f2 lenses for the 645z is not particularly relevant to the way many of these photographers are using their cameras.
fast glass doesn't have to be used wide open, that's a logical fallacy.

the priority is to get a lens that can take a landscape shot at a wider aperture: "Better image quality under larger aperture. IF a 35mm FF lens can be used at a larger aperture, everything you said will be canceled out."

modern fast glass has less vignetting and fewer aberrations all the way up thru f/5.6 at least, so it should always be evaluated for landscape shooting.
04-07-2016, 09:32 AM   #45
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QuoteOriginally posted by itshimitis Quote
If you could get your head from the computer screen you would realise there are many reasons for landscape photographers to shoot with small apertures.
oh? do you have any pics to back up that claim? i think not
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