Split-image focusing for old SLRs - confused

[AgX]

Yes, from a certain degree the size of the split-image in practice would be of influence on its optical features.

However the main reason to limit its size is to keep a great area of groundglass.


As a side note: I got a SLR with a full-image coincidence (superposing) focusing aid. It has it merits, but I miss the groundglass for evalution of DOF and bokeh.

 

[brainmonster]

There is an inherent dualism in the principe of split-image focusing aid, which must show in its design: The grade of acutancy and the ability to use lower speed lenses are inverse to each other.
And a attempt to break this dualism, had shortcomings itself. There are laws of physics which are not dependent on "class" of camera.

I've gotten used to using split image and find it much superior to just a plain matte screen. The images I took with a Zenit E (which had ONLY a matte surface) came out sometimes quite out of focus. I've stopped using my Retina started using more modern cameras like Minoltas, and they all have split image, sometimes with 3 split images in the center or with the image tilted, and all are a small improvements.

However the lack of a microprism collar on the retina is a bit of a shortcoming, but not that much, since you can used the ground glass surface of the rest of the screen, but it seems like the microprism/acute matte field came to be standard in later cameras.

Interestingly, I have a Kiev 6c with ONLY a microprism center-spot focusing aid. I will see how this works. The later Kiev 60 has a microprism collar with split screen center, so it was an "upgrade". But I like the microprism mechanic, which shows a "shimmering" image if the image is out of focus, but which does not function well on small and darkly-colored objects.

 

[AgX]

I've gotten used to using split image and find it much superior to just a plain matte screen.

It is my main means to focus too.

But as I said before, on this matter people here have very divergent penchants.
That is one reason why over time manufacturers offered more and more screens.

 

[Deleted member 88956]

I've gotten used to using split image and find it much superior to just a plain matte screen. The images I took with a Zenit E (which had ONLY a matte surface) came out sometimes quite out of focus. I've stopped using my Retina started using more modern cameras like Minoltas, and they all have split image, sometimes with 3 split images in the center or with the image tilted, and all are a small improvements.

However the lack of a microprism collar on the retina is a bit of a shortcoming, but not that much, since you can used the ground glass surface of the rest of the screen, but it seems like the microprism/acute matte field came to be standard in later cameras.

Interestingly, I have a Kiev 6c with ONLY a microprism center-spot focusing aid. I will see how this works. The later Kiev 60 has a microprism collar with split screen center, so it was an "upgrade". But I like the microprism mechanic, which shows a "shimmering" image if the image is out of focus, but which does not function well on small and darkly-colored objects.

Clear outer circle was carried well into 80's, especially on cameras with interchangeable screens where often both clear and microprisms were used in addition to split. Full microprisms in inner circle (no split image) if done right is quite good though.

 

[Sirius Glass]

Low light and split images do not pay well on some cameras. You can try moving your eye around or use the outer ring of the ground glass background.

 

[George Mann]

This is why autofocus was invented

I prefer to use a better screen such as the Canon EC-A for manual focussing.

 

[Bud Hamblen]

I have a Retina Reflex S from the 1950's, and reading the manual it states that you should match the upper and lower halves of the inner circle in the viewfinder to achieve correct focus. However it seems that sometimes the upper half is not visible due to the way that the light refracts.

The split image focusing aid will black out if your eye isn't centered in the viewfinder eyepiece. Try shifting your eye position a little.

Bud

 

[Sirius Glass]

I switch out the split-image focusing grid for a ground glass with horizontal and vertical guides in my Hasselblad because as the lenses get further away from 80mm the lens apertures are reduced and the split-image problems get obnoxious.

 

[Europan]

However, before it was common, it was sold with some Rectaflexes in the 50's.

Zeiss-Ikon used it, too. The inventor forced the company into a licence contract in 1957. To have a patent doesn’t prevent others from stealing.

 

[AgX]

In this context it should not be overlooked how complicated and expensive it was to make and install those tiny elements within a groundglass. Things only changed when it was possible to make with the needed precision the required tool and plastic moulding of a complete screen.

 

[RLangham]

Zeiss-Ikon used it, too. The inventor forced the company into a licence contract in 1957. To have a patent doesn’t prevent others from stealing.

Zeiss Ikons were quite a bit better than the Rectaflex company's, I can tell you first hand. The split image device in a Contaflex I is as serviceable as any, as good as a Nikkorex F's, in fact, while that in a Rectaflex is almost unusable. They're installed at a 45 degree angle, like a Nikon type L screen, but that's where the similarities end. There's a big gap between the two images, which remains blurry, and the whole thing is so large that it obscures too much of the viewfinder.