What are the restrictions of making the VF?

schmik · 08-06-2009, 04:56 PM

I am amazed at the VF of the pentax ME everytime i put my eye to it. The camera body is tiny and the VF is so large and bright.

My k7 has the magnifying eye cup but still it is smaller than the VF of the ME. BUT the k7 body is quite large in comparison (sheesh imagine the complains of the GIANT handed people if a DSLR was this small).

So it got me thinking, what is the restriction of making the VF bigger? Is it the magnification? EG, film and fullframe size is larger and need less magnification.

Anyone know?

mike

*pbo* · 08-06-2009, 05:29 PM

Eh... maybe the pentaprism size? Just a thought - maybe the older cameras have more space in the housing for a larger pentaprism - since in newer cameras, a lot of space are taken by in-built flash or AE electronics...
Besides, your K-7's sensor area is smaller than that of a 35mm camera - just take off the lenses and compare mirrors side to side - gives an idea. They probably could have made K-7's VF much larger - but then your K-7 would have a huge hump on its top... Look at, say, high-end Canons. or even better, medium format cameras - mine has a pentaprism on top of it, and it's a HUGE chunk of glass that weighs about 200 grams on its own!
Also, magnification is a relative thing. Even if both a film camera and DSLR have same, say, %100 magnification - DSLR's VF will still look smaller (if it's got a crop sensor, that is...) Again, a reference to medium format - even though the VF of my medium format camera is only 94% magnification, image in it is freakishly big compared to that of DSLR, and quite big compared with 35mm.

The brightness issue is another thing - mirrors in DSLR's are coated in such a way that part of the light goes down to sensors - thus VF gets less light. Compromise, I guess.

*pbo* · 08-06-2009, 05:52 PM

Just for fun - here's a Pentax Me and the glass portion from a 645 format camera's prism. Cool huh?

Click on the image to view it in a larger size

*pingflood* · 08-06-2009, 06:28 PM

Two main reasons:

1) The actual amount of light coming in is quite a bit less because of the smaller sensor/mirror.

2) Some light is getting diverted to the AF module.

I still think the finest 35mm SLR viewfinder ever is on the OM2.

For non-SLR, probably the Leica M3.

**Marc Sabatella** · 08-06-2009, 06:29 PM

Although the oiptics in the viewfinder may change this, the basic starting point is this: the image in the viewfinder is the same size as it is on the sensor. Bigger sensor = bigger viewfinder.

schmik · 08-06-2009, 07:14 PM

That's what i thought. That BIG VF sure is nice though.
Damn physics and reallity.... can't we have it all?

mike

snogglethorpe · 08-06-2009, 08:21 PM

I've heard it suggested that one reason they may avoid magnifying the VF image more is that it makes it dimmer, and especially with the big slow zooms many people use these days, it would end up being unacceptably dim.

I also love the huge bright VFs on film cameras...

[argh... while reading this thread I pulled out my 6x7 to look through the VF, and noticed a roll of exposed film stuffed into the case! How many years has that been sitting there...?]

tr13 · 08-06-2009, 10:48 PM

Bright viewfinder is always better.
But human eye adopts to low light very good.
If you keep staring in "dark" viewfinder for a shile you'll get same picture as someone who constantly interrupts to look at bright reality.

24X36NOW · 08-09-2009, 12:31 PM

Originally Posted by schmik

That's what i thought. That BIG VF sure is nice though.
Damn physics and reallity.... can't we have it all?

mike

Sure we can - if they'd just make a FF dSLR!

**Marc Sabatella** · 08-09-2009, 02:47 PM

That wouldn't be having it all - we'd be giving up the smaller size of APS-C cameras, giving up the advantage in telephoto shooting, and paying quite a large premium for it. But of course, for those for whom those things aren't important, it is true that FF does at least give you the larger viewfinder, plus advantages in noise and in wide angle shooting.

snogglethorpe · 08-09-2009, 05:27 PM

Originally Posted by Marc Sabatella

That wouldn't be having it all - we'd be giving up the smaller size of APS-C cameras, giving up the advantage in telephoto shooting, and paying quite a large premium for it.

Well, certainly telephoto would lose out (I don't care, actually I rather love wide-angle, so FF is a plus for me!), and the cost would increase, but what exactly would change in size with a FF camera?

(1) The sensor itself would be bigger, but compared to the size of the camera, even a FF sensor is not so big

(2) The pentaprism, focusing screen, and VF would have to be larger, but as film cameras like the ME demonstrate, can still be still be pretty small (modern cameras do have the cheezy flash on top of the PP though)

(3) Lens, mount remain the same (and these, along with the mirror box and pentaprism, are a significant lower-bound on DSLR size)

(4) Mirror would be bigger, but mirror box would likely only be slightly different (the depth is defined for historical compatiblity with the lenses, and the front width is defined by the lens mount; again, film cameras demonstrate that a FF 35mm mirror system can be very small)

(5) Electronics, display, controls, memory card, etc, would all be the same size as APS-C cameras (maybe there would need to be a bit more memory for bigger pictures, but this wouldn't affect the physical size appreciably)

(6) Battery would probably be about the same (I suspect most power is actually used for things like the auto-focus motor and display, and there wouldn't be a significantly higher draw from FF electronics)

I'm not sure why FF cameras from other manuf.s are so freaking huge... (well, granted even their high-end APS-C cameras are huge, so...). I suspect more to support other "pro" features, than the FF format per-se. Also maybe it's simply what the users expect. [Note that Nikon's pro film cameras bloated up immensely in the end too.]

Class A · 08-10-2009, 04:51 AM

Originally Posted by Marc Sabatella

That wouldn't be having it all - we'd be giving up ... the advantage in telephoto shooting ...

Not if the same pixel pitch is kept. In which case you get APS-C performance by simply cropping the FF image. To get K20D/K-7 performance, we'd need a 32.85MP FF sensor. I don't think such a sensor will be available in the next couple of years, but in principle FF does not have a telephoto disadvantage.

*pingflood* · 08-10-2009, 05:11 AM

Originally Posted by Class A

Not if the same pixel pitch is kept. In which case you get APS-C performance by simply cropping the FF image. To get K20D/K-7 performance, we'd need a 32.85MP FF sensor. I don't think such a sensor will be available in the next couple of years, but in principle FF does not have a telephoto disadvantage.

Next couple of years? Wouldn't be surprised if we saw it this year. Sony and Nikon already have 24MP ones. But the manufacturing cost is much greater and will always remain much greater on FF sensors, so APS-C cameras will continue to have a significant price advantage.

bdery · 08-10-2009, 09:55 AM

One thing is being forgotten : cost. Glass costs a lot of money, especially good glass, and shaving the pentaprism size saves money. So manufacturers balance the cost of the glass with the size and quality.

What's more, as others pointed out, the sensor size limits the size of the pentaprism.

**Marc Sabatella** · 08-10-2009, 11:20 AM

Originally Posted by snogglethorpe

Well, certainly telephoto would lose out (I don't care, actually I rather love wide-angle, so FF is a plus for me!), and the cost would increase, but what exactly would change in size with a FF camera?

I'm not saying say they couldn't potentially be made smaller than they currently are, but it just seems logically pretty obvious that whatever one might try to do to keep size down, a camera can be made smaller still if it has a smaller sensor, mirror, and viewfinder assembly. I don't honestly know what prevents someone form making an APS-C body smaller than an ME Super, but the lack of existence proofs makes me assume there is something. Not that anyone necessarily wants something smaller than an ME Super, but again, I'm just addressing the notion of "having it all" versus making compromises.

Also consider - you need a larger lens to get the same field of view in the telephoto range. As others have observed, this isn't *actually* the case if you allow for cropping in order to achieve that, but then, you're still having to make a compromise in your lens choice - in order to get a given FOV, do you get a larger one than necessary to also cover the uncropped sensor (at a smaller FOV), or do you invest in a lens can only be used in cropped mode. Still not quite "having it all".