TargetTalk

Hi,

Has anyone ever tried a varifocal lens? I am trying to get one made to try as I always seem to be between prescriptions - so am in the process of having a varifocal made to suit. But before I finalise the design - has anyone been there and done that? Any advice?

The top will be -0.75 and the bottom -0.5 (or possibly -1.0 to -0.25) the sweet spot will be in the narrow vertical slice in the middle.

I am also seeking a -0.625 lens as a fixed strength to replace my -0.75 and -0.5s I always seem to be swapping between.

Cheers
Alan

Assuming that you mean a progressive 'varifocal' lens as found in spectacles (not a varifocal camera lens - might be a bit bulky :) ), I use them all the time OTHER THAN FOR SHOOTING.

Either hydraulic (https://en.wikipedia.org/wiki/Adjustabl ... eyeglasses) or mechanical (Alvarez) adjustable focus might be a better option.

Have you tried an adjustable iris? It should increase depth of field.
Try drilling 2 3 4 or 5mm holes in opaque card to test the idea and tape to the eye side of the lens.

My advice? Forget it!

You need only one lens that will allow you to focus only on your front sight. You can get it to fix other problems (astigmatism?) as well.

If you should want to use an iris on anything else it will be a problem. You don't use an iris to increase depth of field, (it WILL do that) but its purpose is to give you a uniform "pupil" size in different lighting conditions.

Do a search for "shooting glasses" here on TT.

Can't agree. As you get older and presbyopia sets in, depth of field becomed more important and the iris does that. It is fine getting the foresight in focus but if the rearsight is a complete blur, not just a bit fuzzy, it is very difficult to get any sight picture. It's a personal thing (I used one for many years) but if 1/8 diopter change is sought I suspect old eyes. Maybe I am wrong.

I have an iris, but never used it. BUT Rover is right, what I want is the perfect prescription to focus on the front sight. And that is the problem, -0.5 is too weak, -0.75 is too strong. I can shoot with either but I am working hard to focus. A lens in between is what I want, but not found a supplier yet who does a -0.625. Hence the thought that a varifocal may allow me to find the sweet spot.

I am also aware that I've spent a small fortune on lenses as my prescription has changed from -0.25 down to current prescription of -0.5. A varifocal may give some room for future change if my eye continues to change.

Try a Variolens. http://variolens.com/english.html

It's a lens that can be adjusted, specifically made for shooting. The only drawback is that if you need astigmatism correction, you'll need an additional lens.

mctrucky wrote:I have an iris, but never used it. BUT Rover is right, what I want is the perfect prescription to focus on the front sight. And that is the problem, -0.5 is too weak, -0.75 is too strong. I can shoot with either but I am working hard to focus. A lens in between is what I want, but not found a supplier yet who does a -0.625. Hence the thought that a varifocal may allow me to find the sweet spot.

I am also aware that I've spent a small fortune on lenses as my prescription has changed from -0.25 down to current prescription of -0.5. A varifocal may give some room for future change if my eye continues to change.

I recommend you try the iris for one session.

Maybe I should have been more clear, unlike what some are recommending.

What you want is one PRESCRIPTION lens that allows you to focus on the front sight while correcting what eye defects it may. If you need it down to halfway between .50 and .75, then ORDER that, although I suspect a +.50 will be fine. If you eventually need further correction, then you can order a + or - lens in addition to the above and stack them (we're talking about shooting glasses such as Champion, etc. here). An iris is optional...I see many top shooters with good eyesight NOT using them. Don't expect any major help from an iris.

Rover wrote: An iris is optional...I see many top shooters with good eyesight NOT using them. Don't expect any major help from an iris.

An iris WILL increase depth of field for presbyopic older shooters once set below natural pupil size, you can't deny laws of physics. Ask any photographer. Whether you like the trade off with lower light levels is personal preference. What I cannot understand is not trying it when you own one.

TenMetrePeter wrote:

Rover wrote: What I cannot understand is not trying it when you own one.

Fair point - I bought one a few years ago, but before it arrived my coach, an ex World Class shooter, explained they were the work of the devil. So it was cast to the back of the cupboard.
I have not reached world class, but have shot in a couple of world cups and the world championship - but making up the numbers as part of gaining experience. Accident and injury have stopped me improving at the rate needed and I am no longer shooting the MCS to get back on the world stage, but that is my ambition for 2017 and 2018.
Now my eyesight is one of those variables, which at my age (50) is not getting any better, so I am looking outside the box for any improvements I can get. I will try the iris - as you point out, bit mad not to when I own one. But what I really want is the correct prescription, but they are made in 0.25 increments and I want a 0.125 increment - hence the varifocal question. If you know different please let me know where I can mail order this..
I have seen and tried the fluid filled adjustable lens, and found it 'cloudy'. I have also seen one leaking and the shooter coping with an air bubble that caused all sorts of distortions - and for me, I don't want that risk of it going wrong when I need it most. I want to simplify things, not increase complexity.

mctrucky wrote:

TenMetrePeter wrote:

Rover wrote: What I cannot understand is not trying it when you own one.

Fair point - I bought one a few years ago, but before it arrived my coach, an ex World Class shooter, explained they were the work of the devil.

I would agree with him. They cut down the amount of light entering the eye.

IMHO the only useful thing you can do with an iris is set it at about 4mm and just use it as a reference to make sure you're looking through the centre of the lens.

As for varifocals/progressive focus lenses, for shooting? You want to remove the variables not increase them. How will you know that you're looking through the same bit of the lens each time.

David Levene wrote: As for varifocals/progressive focus lenses, for shooting? You want to remove the variables not increase them. How will you know that you're looking through the same bit of the lens each time.

By looking at the foresight. If it is in focus and crisp, then I'm good to go.

With a regular lens, you can look through most of the lens and get the same focal depth, meaning your head can be in different positions, looking at an angle, high, low, whatever and you don't know. With a 'sweet spot' on a varifocal, perhaps alignment will be more consistent, not less?

mctrucky wrote:

David Levene wrote: As for varifocals/progressive focus lenses, for shooting? You want to remove the variables not increase them. How will you know that you're looking through the same bit of the lens each time.

By looking at the foresight. If it is in focus and crisp, then I'm good to go.

With a regular lens, you can look through most of the lens and get the same focal depth, meaning your head can be in different positions, looking at an angle, high, low, whatever and you don't know. With a 'sweet spot' on a varifocal, perhaps alignment will be more consistent, not less?

I wear progressive lenses Alan, but there's no way I'd wear them for shooting.