Make your own bifocal diopter!

[Huss]

I have a Pentax SuperA that has small LCD exposure numbers in the viewfinder (at the bottom). They were blurry as my eyes are not what they were. Even though what I was focusing on was sharp.
I bought a +2 diopter to see if that would help. That made the numbers sharp, but now the image was slightly blurry! So I bought a glass cutting tool from the hardware shop ($5), and cut away the top 2/3 of the diopter. To do that I took the glass out of the plastic holder.
Now I can see the numbers clearly, and I can see what I need to focus on! Hey presto, bifocal diopter!

 

[Paul Howell]

Nice hack.

 

[jgoody]

Slick!!

 

[CMoore]

I have a Pentax SuperA that has small LCD exposure numbers in the viewfinder (at the bottom). They were blurry as my eyes are not what they were. Even though what I was focusing on was sharp.
I bought a +2 diopter to see if that would help. That made the numbers sharp, but now the image was slightly blurry! So I bought a glass cutting tool from the hardware shop ($5), and cut away the top 2/3 of the diopter. To do that I took the glass out of the plastic holder.
Now I can see the numbers clearly, and I can see what I need to focus on! Hey presto, bifocal diopter!

Going to be a few weeks before another member will "Out-Clever" you on this bit of ingenuity.

 

[AgX]

A good solution, but I wonder wjhy the LCD display is out of focus in first instance.

 

[ic-racer]

A good solution, but I wonder wjhy the LCD display is out of focus in first instance.

I have cameras like that (the numbers don't appear to be at the same focal point as the focus screen). My theory was that the simple viewfinder optics are not flat field. One might need a viewfinder with six elements for a perfectly corrected field.

 

[AgX]

The eyepiece must be flat field. Otherwise there at least would be unsharp corners at the groundglass image.

 

[Huss]

The eyepiece must be flat field. Otherwise there at least would be unsharp corners at the groundglass

The Pentax diopter is not flat, but curved.

 

[ic-racer]

The eyepiece must be flat field. Otherwise there at least would be unsharp corners at the groundglass

True. On second thought it may be the human eye's horrible chromatic aberration. My worst camera with this issue is Rolleiflex 3003 with LED readout. The red light is horribly out of focus in my eye.

 

[AgX]

The Pentax diopter is not flat, but curved.

The term flat field does not refer to the shape of an optical element, but to its focal plane.

 

[Huss]

The term flat field does not refer to the shape of an optical element, but to its focal plane.

Then I guess Pentax curves that diopter to maintain the flat field!