Why have Pentax viewfinders got 'smaller' through time?

thetrooper · 11-06-2021, 11:30 AM

Apologies in advance if this has been answered elsewhere, but I was wondering if anyone knows why Pentax full-frame viewfinders (both film and digital) have reduced in magnification through time?

In terms of Pentax cameras I own, I would say that the viewfinder image size is best with the older film bodies, and worst with my K1 Mk2. Using the same A-series 50mm f1.4 lens on each, I would rate them (from best to worst) as:

ME Super
LX
Z-1P (PZ-1P)
MZ-S
K1 Mk2

I'd be really interested in knowing why this might be - I'm sure there is a solid technical reason - but modern viewfinders just don't seem to be such an immersive experience as they are on the old film bodies.

Thanks.

Adam · 11-06-2021, 11:53 AM - **5 Likes**

It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next.

stevebrot · 11-06-2021, 12:10 PM - **3 Likes**

Originally posted by thetrooper

I would rate them (from best to worst) as:

ME Super
LX
Z-1P (PZ-1P)
MZ-S
K1 Mk2

I agree with your rankings. The late 1970s into the 1980s represents the historic high point for manual focus SLR viewfinder performance, across brands. The view is like looking out a window with close to full coverage at near 100% magnification with a 50mm lens at infinity.

Why did things change? The short answer is that the direct blame for reduced magnification goes to auto focus using PDAF. The talking points go like this:

The PDAF sensor is located in the floor of the mirror box and gets its image courtesy of a partially-silvered main mirror acting as a beam splitter.
Since the amount of light being delivered to the optical viewfinder is significantly reduced, the point of compromise in terms of brightness is made up by using lower magnification while retaining reasonable coverage. As a result, the view is sort of like looking down a tunnel.
The view could be worse, but use of focus screen brightening treatments and pentaprism rather than pentamirror help ease the pain for recent model Pentax dSLR owners.

Steve

**Alex645** · 11-06-2021, 12:14 PM

Originally posted by Adam

It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next.

+1 @Adam. Notice that the manual focus cameras are at the top of your list, followed by AF, then digital. My Pentax 645 has a greater magnification than my 645N, and I assume that's also due to the addition of AF.

I'd also add that with the option of LiveView, the OVF is less of design concern. But as DSLR are now trying to survive against Mirrorless, Pentax made a wise improvement for the K3iii viewfinder. For those of us that shoot a lot and with OVF, it makes a big difference. For the casual photographer, they don't seem to notice.

angerdan · 11-06-2021, 12:21 PM - **2 Likes**

Originally posted by thetrooper

Apologies in advance if this has been answered elsewhere, but I was wondering if anyone knows why Pentax full-frame viewfinders (both film and digital) have reduced in magnification through time?
In terms of Pentax cameras I own, I would say that the viewfinder image size is best with the older film bodies, and worst with my K1 Mk2.

The coverage did increase while the magnification decreased:

Brand / Model	Coverage	Magnification	Crop Factor	Effective Size
Pentax MX	97%	0.95	1	0.92
Pentax LX	95%	0.92	1	0.87
Pentax 645Z	98%	0.62	0.8	0.76
Pentax K-3 III	100%	1.05	1.5	0.70
Pentax K-1	100%	0.7	1	0.70

aaacb · 11-06-2021, 12:24 PM - **1 Like**

My understanding is that, as a design goal, magnification competes with coverage, eyepoint and cost. See this explanation: Understanding Viewfinders - Luminous Landscape

So at least for the K1ii, I like that they're going for 100% coverage and decent eyepoint, it helps me see the final image well when wearing eyeglasses. For manual focus cameras, I'm happy to trade size over other aspects because of focus accuracy, though it's certainly possible to manual focus with the k1ii as well. And for the new k3iii viewfinder, my guess is that it's quite a bit more expensive than the one in the k1ii, judging by the development stories shared part of the camera launch.

**RobA_Oz** · 11-06-2021, 01:35 PM

Originally posted by BROO

My assumption is the K-3 mkIII high-refraction glass pentaprism is part of a series of development goals leading towards a hybrid viewfinder. (being used in conjunction with a pelical mirror).
Hopefully to be introduced in a 645Z mkIII providing it is not cost prohibitive?

The OVF in the K-3iii is startlingly good, when compared with previous APS-C offerings, so a K-1iii with the same pentaprism glass plus the new VF information focussing screen overlay should get things back towards the old film camera visibility. Replacing the mirror with a pellical arrangement will work the other way, of course, but may offer other advantages.

Doing likewise with a 645Z replacement could make its viewfinder magnificent, particularly if the sensor is upgraded to full-frame.

Of course, in all cases, the trade-off between magnification and brightness will be a matter for the designer’s judgment.

PS: I should add that the LX’s “sports” viewfinder was outstandingly bright, but that’s because it had a lower magnification, as I recall.

Last edited by RobA_Oz; 11-06-2021 at 07:48 PM.

Not a Number · 11-06-2021, 02:22 PM

The reason I read about 35mm film SLRs viewfinders having less than 100% coverage was because of the partial masking of the 35mm frame from slide mounts. The cutoff in the viewfinder was to aid in composition of slides.

thetrooper · 11-06-2021, 03:42 PM - **1 Like**

Thanks for the great answers everyone.

I agree that a K1 Mk3 with the viewfinder tech of a K3 Mk3 would be a fantastic OVF experience. I hope something like that does become reality.

Paul the Sunman · 11-06-2021, 08:35 PM

Originally posted by thetrooper

Thanks for the great answers everyone.

I agree that a K1 Mk3 with the viewfinder tech of a K3 Mk3 would be a fantastic OVF experience. I hope something like that does become reality.

The new pentaprism in the K3iii is physically larger than those in earlier APS-C cameras, which may have been responsible for the absence of GPS. I'm not sure I would make that trade in a K1iii.

**Mikesul** · 11-06-2021, 09:10 PM

The K-3iii is great in most respects but I would gladly trade the new viewfinder for the built-in GPS. I have no problems with phone GPS but the built-in unit on the K-3ii an K-1ii are nicer.

**Alex645** · 11-07-2021, 01:42 AM

Originally posted by Not a Number

The reason I read about 35mm film SLRs viewfinders having less than 100% coverage was because of the partial masking of the 35mm frame from slide mounts. The cutoff in the viewfinder was to aid in composition of slides.

Yes that was part of it, but also the 24x36mm image is not proportionate to the common 5x7", 8x10", 11x14", 16x20" paper print sizes. Yes, 4x6", 5x8", 8x12", etc, became common in color print papers, but never caught on in black and white.

Nevertheless, I still want to see 100% and decide myself what I will crop later. That's why I opted for a Nikon F3HP back in the 80's. Major kudos to the K1 and K3iii for 100% viewfinder coverage.

**niels hansen** · 11-07-2021, 11:52 AM

Originally posted by Adam

It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next.

I dont agree that af makes precise manual focusing in eyeview unnessecary because pdaf has limitations. Live view is onlly an option with rather static motives. If the market had made it possible I would gladly have bought a dslr without af, but with un impressive mf.
my age and bank account states that I dont buy a new camera anymore

stevebrot · 11-07-2021, 12:04 PM

Originally posted by niels hansen

I dont agree that af makes precise manual focusing in eyeview unnessecary because pdaf has limitations.

Yep...huge imprecision overall when compared to better manual focusing methods.

Steve

Andrea K · 11-08-2021, 09:39 AM

Originally posted by thetrooper

Apologies in advance if this has been answered elsewhere, but I was wondering if anyone knows why Pentax full-frame viewfinders (both film and digital) have reduced in magnification through time?

In terms of Pentax cameras I own, I would say that the viewfinder image size is best with the older film bodies, and worst with my K1 Mk2. Using the same A-series 50mm f1.4 lens on each, I would rate them (from best to worst) as:

ME Super
LX
Z-1P (PZ-1P)
MZ-S
K1 Mk2

I'd be really interested in knowing why this might be - I'm sure there is a solid technical reason - but modern viewfinders just don't seem to be such an immersive experience as they are on the old film bodies.

Thanks.

So you don't own an MX...

11-06-2021, 11:30 AM	#1
thetrooper New Member Join Date: Jul 2020 Location: Hampshire, England Posts: 6	Why have Pentax viewfinders got 'smaller' through time? Apologies in advance if this has been answered elsewhere, but I was wondering if anyone knows why Pentax full-frame viewfinders (both film and digital) have reduced in magnification through time? In terms of Pentax cameras I own, I would say that the viewfinder image size is best with the older film bodies, and worst with my K1 Mk2. Using the same A-series 50mm f1.4 lens on each, I would rate them (from best to worst) as: ME Super LX Z-1P (PZ-1P) MZ-S K1 Mk2 I'd be really interested in knowing why this might be - I'm sure there is a solid technical reason - but modern viewfinders just don't seem to be such an immersive experience as they are on the old film bodies. Thanks.

11-06-2021, 11:53 AM - 5 Likes	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

11-06-2021, 12:10 PM - 3 Likes	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by thetrooper I would rate them (from best to worst) as: ME Super LX Z-1P (PZ-1P) MZ-S K1 Mk2 I agree with your rankings. The late 1970s into the 1980s represents the historic high point for manual focus SLR viewfinder performance, across brands. The view is like looking out a window with close to full coverage at near 100% magnification with a 50mm lens at infinity. Why did things change? The short answer is that the direct blame for reduced magnification goes to auto focus using PDAF. The talking points go like this: The PDAF sensor is located in the floor of the mirror box and gets its image courtesy of a partially-silvered main mirror acting as a beam splitter. Since the amount of light being delivered to the optical viewfinder is significantly reduced, the point of compromise in terms of brightness is made up by using lower magnification while retaining reasonable coverage. As a result, the view is sort of like looking down a tunnel. The view could be worse, but use of focus screen brightening treatments and pentaprism rather than pentamirror help ease the pain for recent model Pentax dSLR owners. Steve Last edited by stevebrot; 11-06-2021 at 01:05 PM. Reason: ambiguity

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11-06-2021, 12:14 PM	#4
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by Adam It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next. +1 @Adam. Notice that the manual focus cameras are at the top of your list, followed by AF, then digital. My Pentax 645 has a greater magnification than my 645N, and I assume that's also due to the addition of AF. I'd also add that with the option of LiveView, the OVF is less of design concern. But as DSLR are now trying to survive against Mirrorless, Pentax made a wise improvement for the K3iii viewfinder. For those of us that shoot a lot and with OVF, it makes a big difference. For the casual photographer, they don't seem to notice.

11-06-2021, 12:24 PM - 1 Like	#6
aaacb Pentaxian Join Date: May 2016 Photos: Gallery Posts: 3,725	My understanding is that, as a design goal, magnification competes with coverage, eyepoint and cost. See this explanation: Understanding Viewfinders - Luminous Landscape So at least for the K1ii, I like that they're going for 100% coverage and decent eyepoint, it helps me see the final image well when wearing eyeglasses. For manual focus cameras, I'm happy to trade size over other aspects because of focus accuracy, though it's certainly possible to manual focus with the k1ii as well. And for the new k3iii viewfinder, my guess is that it's quite a bit more expensive than the one in the k1ii, judging by the development stories shared part of the camera launch.

11-06-2021, 01:35 PM	#7
RobA_Oz Site Supporter Join Date: Nov 2008 Location: Tasmania, Australia Photos: Gallery Posts: 8,197	Originally posted by BROO My assumption is the K-3 mkIII high-refraction glass pentaprism is part of a series of development goals leading towards a hybrid viewfinder. (being used in conjunction with a pelical mirror). Hopefully to be introduced in a 645Z mkIII providing it is not cost prohibitive? The OVF in the K-3iii is startlingly good, when compared with previous APS-C offerings, so a K-1iii with the same pentaprism glass plus the new VF information focussing screen overlay should get things back towards the old film camera visibility. Replacing the mirror with a pellical arrangement will work the other way, of course, but may offer other advantages. Doing likewise with a 645Z replacement could make its viewfinder magnificent, particularly if the sensor is upgraded to full-frame. Of course, in all cases, the trade-off between magnification and brightness will be a matter for the designer’s judgment. PS: I should add that the LX’s “sports” viewfinder was outstandingly bright, but that’s because it had a lower magnification, as I recall. Last edited by RobA_Oz; 11-06-2021 at 07:48 PM.

11-06-2021, 02:22 PM	#8
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	The reason I read about 35mm film SLRs viewfinders having less than 100% coverage was because of the partial masking of the 35mm frame from slide mounts. The cutoff in the viewfinder was to aid in composition of slides.

11-06-2021, 03:42 PM - 1 Like	#9
thetrooper New Member Join Date: Jul 2020 Location: Hampshire, England Posts: 6 Original Poster	Thanks for the great answers everyone. I agree that a K1 Mk3 with the viewfinder tech of a K3 Mk3 would be a fantastic OVF experience. I hope something like that does become reality.

11-06-2021, 08:35 PM	#10
Paul the Sunman Pentaxian Join Date: Aug 2011 Location: Melbourne Photos: Gallery Posts: 4,843	Originally posted by thetrooper Thanks for the great answers everyone. I agree that a K1 Mk3 with the viewfinder tech of a K3 Mk3 would be a fantastic OVF experience. I hope something like that does become reality. The new pentaprism in the K3iii is physically larger than those in earlier APS-C cameras, which may have been responsible for the absence of GPS. I'm not sure I would make that trade in a K1iii.

11-06-2021, 09:10 PM	#11
Mikesul Loyal Site Supporter Join Date: Sep 2009 Location: Phoenix, AZ Posts: 7,594	The K-3iii is great in most respects but I would gladly trade the new viewfinder for the built-in GPS. I have no problems with phone GPS but the built-in unit on the K-3ii an K-1ii are nicer.

11-07-2021, 01:42 AM	#12
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by Not a Number The reason I read about 35mm film SLRs viewfinders having less than 100% coverage was because of the partial masking of the 35mm frame from slide mounts. The cutoff in the viewfinder was to aid in composition of slides. Yes that was part of it, but also the 24x36mm image is not proportionate to the common 5x7", 8x10", 11x14", 16x20" paper print sizes. Yes, 4x6", 5x8", 8x12", etc, became common in color print papers, but never caught on in black and white. Nevertheless, I still want to see 100% and decide myself what I will crop later. That's why I opted for a Nikon F3HP back in the 80's. Major kudos to the K1 and K3iii for 100% viewfinder coverage.

11-07-2021, 11:52 AM	#13
niels hansen Site Supporter Join Date: Aug 2017 Posts: 343	Originally posted by Adam It's likely due to autofocus, because AF cameras don't need precise manual focusing aides in the viewfinder. That said, it seems this trend may start reversing itself- the viewfinder on the K-3 III is just as big as the K-1 viewfinder. It will be interesting to see where things go next. I dont agree that af makes precise manual focusing in eyeview unnessecary because pdaf has limitations. Live view is onlly an option with rather static motives. If the market had made it possible I would gladly have bought a dslr without af, but with un impressive mf. my age and bank account states that I dont buy a new camera anymore

11-07-2021, 12:04 PM	#14
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by niels hansen I dont agree that af makes precise manual focusing in eyeview unnessecary because pdaf has limitations. Yep...huge imprecision overall when compared to better manual focusing methods. Steve

11-08-2021, 09:39 AM	#15
Andrea K Pentaxian Join Date: Mar 2009 Location: Rome, Italy Posts: 822	Originally posted by thetrooper Apologies in advance if this has been answered elsewhere, but I was wondering if anyone knows why Pentax full-frame viewfinders (both film and digital) have reduced in magnification through time? In terms of Pentax cameras I own, I would say that the viewfinder image size is best with the older film bodies, and worst with my K1 Mk2. Using the same A-series 50mm f1.4 lens on each, I would rate them (from best to worst) as: ME Super LX Z-1P (PZ-1P) MZ-S K1 Mk2 I'd be really interested in knowing why this might be - I'm sure there is a solid technical reason - but modern viewfinders just don't seem to be such an immersive experience as they are on the old film bodies. Thanks. So you don't own an MX...