[stevebrot]

So in situations like wildlife photography, where your reach is a function of pixel density amplified by focal length, 150mm on the 645Z is equivalent to 190mm on a 5D3.

Assuming, of course, that you know the actual pixel area available (and actually used) for light gathering and the base signal:noise ratio. All pixels are not created equal.


Steve

(...this (pixel density) being one of the not so solid assumptions...)

[bmw]

My read of what was said is that the concern was over the ability to autofocus or manual focus with the slower lens when wide open - then of course this would be stopped down to whatever the shot required but the open performance limits viewfinder brightness and hence accuracy of the manual focus efforts with modeling lights.

This. Precisely.

---------- Post added 08-08-15 at 02:12 PM ----------

2. DOF is a challenge as the frame size increases. Simply put, at commonly-used focal lengths and working distances f/2.8 is not very useful with the 645Z sensor.

That's interesting, but is not borne out by my experience so far. f/2.8 is great! My 645Z has no trouble focussing at 2.8 in good light (D FA 645 55mm) and the results are wonderful.

---------- Post added 08-08-15 at 02:20 PM ----------

In a studio with mains powered light setups, f5.6 and f8 and even f11 are desired, because you want the image to be super sharp.

If I had a buck for every time somebody has suggested this, I'd be looking at an FA 75mm.

First, final aperture has nothing whatsoever to do with the camera's focussing aperture which is wide open.

Secondly, who says I want super sharp? I often shoot at wider apertures in studio. In portraiture, I prefer a nice sharp plane of focus through a portrait subject's face and everything else to fall into soft blurriness. In fact, that's why I bought a 645Z in the first place: that soft "medium format look". If I wanted f8 and f11 I could have saved myself the price of a small car and stuck with my K-3.

---------- Post added 08-08-15 at 02:25 PM ----------

I'm actually struggling to see the problem. In a studio you often use f8-f11 or thereabouts. It's outside with natural backgrounds that you might want 2.8

So I dealt with that myth above.

However that aside, if you are concerned about focus, live view is your friend.

Yeah, maybe, but not so much. I'm far-sighted; I work the camera largely by feel, and I sure can't see the LCD screen well enough to focus. I'm a dyed-in-the-wool viewfinder guy. I have a loupe for previews but I rarely chimp after the initial setup, so that's not too useful.

I tried live-view and even focus peaking on my K-3 and gave it up as useless for me.[COLOR="Silver"]

---------- Post added 08-08-15 at 02:28 PM ----------

I should add, as a followup, that ordered my 645Z along with the D FA 55mm 2.8 and the D FA 90mm 2.8 macro lenses. I have been playing with the 645/55mm combos so far while waiting for the 90mm and I'm loving it. I think I'll be able to get along fine without the bulky zooms, at least for now. We'll see how it goes in the longer run.

Thanks everybody for weighing in.

[Kolor-Pikker]

Assuming, of course, that you know the actual pixel area available (and actually used) for light gathering and the base signal:noise ratio. All pixels are not created equal.

Steve

(...this (pixel density) being one of the not so solid assumptions...)

Good thing then that 645Z pixels are objectively better than the pixels on every other camera ever made.

On the Leica forums I frequent, any mention of equivalence will be followed by complete silence. Leicaphiles do not tolerate Noobs....especially ones that only have a Hexar RF.

Wrong kind of equivalence haha.

The important thing is about how photographers use their systems, and more often than not we fall back on tried and true techniques to get our shots. We have our wide angles, normals, and tele lenses, most of which fall into a limited and predictable set that we use fairly repeatedly.
A lens set at 65mm f/4.5 on the 645Z is "not really" like shooting 50mm f2.8 on a Canon or other, but from a practical stand point, I'd probably get a similar shot from either one having adjusted the settings appropriately... not because I'm actively trying to get an equivalent image, but because I'm subconsciously trying to get a look I want. Sometimes it just pays to know the technical reason as to the why and how.

[LensBeginner]

*snip*

I should add, as a followup, that ordered my 645Z along with the D FA 55mm 2.8 and the D FA 90mm 2.8 macro lenses. I have been playing with the 645/55mm combos so far while waiting for the 90mm and I'm loving it. I think I'll be able to get along fine without the bulky zooms, at least for now. We'll see how it goes in the longer run.

Thanks everybody for weighing in.

A truly farsighted choice (pun intended)!
Hope you enjoy it and get memorable pictures with it.

[rfkiii]

When talking about equivalence, keep things like pixel density in mind more than mere conversion of focal lengths.
For instance, 150mm on the 645Z is like 130mm on FF35, but the pixel density is around 45% higher than a Canon 5D2/3. If those are the cameras you're used to using, you will find that you'll still get more pixels on the subject despite the wider FoV.
So in situations like wildlife photography, where your reach is a function of pixel density amplified by focal length, 150mm on the 645Z is equivalent to 190mm on a 5D3.

My situation is this: I have been using the Tamron 150-600 on a D800E -> for landscapes. I've become quite addicted to this perspective. I've recently sold this setup and was considering a Tamron or Sigma 150-600 on a 5DsR (when one becomes available) but I also had the thought that the 645 FA 400mm on a 645z might be a viable option because as you said elsewhere the 645z has the best pixels of any DSLR (or words to that effect and I agree). Well, I want to buy this 400mm from a Japanese dealer off eBay. Basically, in this situation, if you buy it, you keep it. So, the question being for me, is the 'reach' comparable? With the D800 in mind, what do you estimate the equivalent FOV/reach to be of this 400mm on a 645z? TIA

[rfkiii]

Truly...You mean people like me?

I don't know what you mean by this. I wrote, "some folks" and that may or may not include you. Apparently not. Actually, I think you misread my post as I essentially agreed with you with one reservation.

[stevebrot]

I don't know what you mean by this.

Taken in context...

Equivalence has long been a big deal to users of the 35mm format.

My point of disagreement...

Truly...You mean people like me?

My attempt at irony.

I am a long-time 35mm photographer and the thought of "equivalence" in the current sense of the term truly never crossed my mind nor had I heard of the concept until reading some relatively recent posts on this site. Comparative field of view across formats, yes...equivalent DOF, total light, S/N, etc. (all expressed as "stops"), no. IMHO, "Equivalence" was thought up as a way to justify the acceptability (superiority?) of a user's choice of format/camera and has as much real world relevance for most photog as 8 vs. 10 FPS.


Steve

---

Last edited by stevebrot; 08-09-2015 at 01:26 PM.

[Kolor-Pikker]

My situation is this: I have been using the Tamron 150-600 on a D800E -> for landscapes. I've become quite addicted to this perspective. I've recently sold this setup and was considering a Tamron or Sigma 150-600 on a 5DsR (when one becomes available) but I also had the thought that the 645 FA 400mm on a 645z might be a viable option because as you said elsewhere the 645z has the best pixels of any DSLR (or words to that effect and I agree). Well, I want to buy this 400mm from a Japanese dealer off eBay. Basically, in this situation, if you buy it, you keep it. So, the question being for me, is the 'reach' comparable? With the D800 in mind, what do you estimate the equivalent FOV/reach to be of this 400mm on a 645z? TIA

The 645Z has about 30.5MP if you were to crop the physical sensor down to 24x36mm, placing it's "reach" somewhere between a 5D3 and D800, or a much lower magnification than you would get with the 5DsR.

Since both the Z and 5D have similar resolution, the calculation is quite simple, the 5D will have 1.7x the reach of the Z at any given focal length. 400mm on the 5D would require a 680mm lens on the Z, and the Z at 400mm gives the same reach as the 5D would get at 235mm.

But I stress that this is a "pixels per duck" scenario where you really need to place the most resolution on a distant subject - if you do however, then the increased resolution of the 5DsR may provide more benefit than lower noise floor of the 645Z, especially if shooting in good light.

[rfkiii]

Taken in context...



My point of disagreement...



My attempt at irony.

I am a long-time 35mm photographer and the thought of "equivalence" in the current sense of the term truly never crossed my mind nor had I heard of the concept until reading some relatively recent posts on this site. Comparative field of view across formats, yes...equivalent DOF, total light, S/N, etc. (all expressed as "stops"), no. IMHO, "Equivalence" was thought up as a way to justify the acceptability (superiority?) of a user's choice of format/camera and has as much real world relevance for most photog as 8 vs. 10 FPS.


Steve

To Stevebrot.


I see my writing mistake. I failed to qualify "users of the 35mm format". I should have said "some" users of the 35mm format, I was certainly thinking "some", or perhaps even "many", but obviously not "all". But, I do not know why equivalence would not be of interest to users of the 645 sensor/film size if and when they consider purchasing legacy 645 lenses (since the 645z is a cropped 645) or adapting 67 lenses. After purchasing a given lens for the system, during use, I do not think in terms of "I am currently shooting an equivalent 21mm with a 28mm 645 lens." I am thinking about what is framed in the VF. This is where I agree with you. Equivalence is gone from my mind.

[rfkiii]

The 645Z has about 30.5MP if you were to crop the physical sensor down to 24x36mm, placing it's "reach" somewhere between a 5D3 and D800, or a much lower magnification than you would get with the 5DsR.

Since both the Z and 5D have similar resolution, the calculation is quite simple, the 5D will have 1.7x the reach of the Z at any given focal length. 400mm on the 5D would require a 680mm lens on the Z, and the Z at 400mm gives the same reach as the 5D would get at 235mm.

But I stress that this is a "pixels per duck" scenario where you really need to place the most resolution on a distant subject - if you do however, then the increased resolution of the 5DsR may provide more benefit than lower noise floor of the 645Z, especially if shooting in good light.

Yes sir. I understand. It's math that I do not.



Since I have been shooting the 150-600 with the D800E (@ 36 MPs) and I am familiar with its product, would the conversion factor be roughly 1.18x?


The 5DsR was going to be my dedicated camera for the 11-24L since I do not see Pentax dipping this wide in the 645 arena. But, it could also serve as a mount for a 150-600 type lens if Nikon does not enter the 50 MP club in the foreseeable future.

[Kolor-Pikker]

Since I have been shooting the 150-600 with the D800E (@ 36 MPs) and I am familiar with its product, would the conversion factor be roughly 1.18x?

At equal focal lengths the detail difference may be small enough so as not to be important, but the Z will offer a wider field of view.

The 5DsR was going to be my dedicated camera for the 11-24L since I do not see Pentax dipping this wide in the 645 arena. But, it could also serve as a mount for a 150-600 type lens if Nikon does not enter the 50 MP club in the foreseeable future.

Well, the DSLR is going to be the lighter and more flexible option, plus you'll get in-lens stabilization. Sure has it's merits.
If you're going to get a 5DsR anyway just to use the 11-24, there's really no reason to also get the 645Z.

[normhead]

I have an A-55 ƒ2.8 645 in my cupboard , and it's neither large nor at all cumbersome. I know you're talking zooms, but for MF, maybe a handful of primes is the way to go.

[Lacunapratum]

I agree with normhead. I want primes. Fast primes.

I am worried that the current execs at Ricoh treat the Pentax camera business like their copy machines. Lenses are different. I hope they get that.

[Kolor-Pikker]

I am worried that the current execs at Ricoh treat the Pentax camera business like their copy machines. Lenses are different. I hope they get that.

Well hey now, we have a big old Ricoh Aficio at the office and it is super rock solid, I'm sure that after all these years many of the internal components are well past their service life, but it just works. Nothing had to be swapped out but the dyes till now, knocking on wood.

I'm still waiting to see what Pentax comes up with for their zooms, as it's a fairly interesting way to take the system. Most MF systems focus on primes while the zoom lenses are variable-aperture afterthoughts, but Pentax is putting a decent effort in. Assuming one doesn't need faster than f/4.5, you'll be able to cover 28-160mm with three lenses soon enough.

Quite frankly, the more I use the system, the less I'm inclined to waste all those pixels on bokeh. Having a couple of fast f/2 primes would be nice for the odd low light or portrait shot, but large sensor cameras are dangerously starved for DoF, even at seemingly normal apertures. Even now, I still often shoot at say f/5.6 only to not get as much in focus as I expected, because the same aperture on 35mm would get a lot more in.

That said a 100mm f/2 lens with an at least 1/800th leaf shutter would do wonders for the system.

[tuco]

This is quite likely a really dumb question, but as a medium format total newb, I have to ask it.

I'm planning the Big Move from K-3 to 645Z.

I haven't read all the posts and apologize if this was already covered.

But on the the first page of the thread people are saying f4.5 is the same as f2.8 in terms of DOF and other generalizations about medium format. While this is true you specifically mention the 645Z. F4.5 is a slow lens on that camera too and f4.5 is not equal to f2.8 DOF of a small format camera for the Z.

Bear in mind a couple of things. Firstly, the 6x4.5 cm film format is small size for legacy medium format. And secondly the approximate normal lens on a Z is 55mm and for a 35mm format camera it is as you know 50mm. But on a 6x4.5 format it is 75mm. Maybe that will help place things in perspective. And also note the Pentax 6x7 has a roughly normal lens of 105mm f2.4 and I use f2.8 on that lens quite frequently these days.