Correct diopter for -1.25?

[Spiritualized67]

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Does anyone know the correct diopter I should get for -1.25? I have an M4. I ordered -1.0 from B&H but not sure if that was the correct choice? I don't really have Astigmatism.

 

I've read conflicting info on whether or not to include the -0.50 that is inherent in the VF.

 

 

Any advice would be appreciated, as -1.25 falls in-between all values.

 

 

-Dan

[Guido]

You really should test this in practice if possible. For example, I needed 0.75 in theory and went to the store with the expectation of buying 0.5, but then changed my mind after switching back and forth between 0.5 and 1.0 several times on my camera in the store.

 

The -0.5 in the VF does not need to be included. Otherwise, every normal-sighted owner would need to buy a +0.5 dioptre to use the camera.

[Spiritualized67]

Thank you. I went ahead and ordered the -0.5, -1.0 and -1.5 from B&H - and should be able to determine the ideal correction (and return the others). I appreciate the response.

 

~Dan

[Spiritualized67]

Surprisingly, I ended up going with the -1.5, even though I thought the -1 would be the perfect choice prior to trying it.

 

-0.5 was a meaningless correction as many others had suggested. So it came down to -1.0 or -1.5.

 

Given that my eye test indicated -1.25 and factoring in the factory M4 VF preset of -0.5, logic would dictate that I should go with a -0.75 diopter (which is not an available choice). Many folks suggested going with a slightly stronger diopter, which is why I thought rounding the correction up to the -1.0 would be perfect.

 

But in real-world focusing, the -1.5 seemed to be easier for me. I think part of the reason is the image is slightly more magnified than -1.0, and that extra magnification makes all the difference in the world for critical focus, especially for distant objects.

 

I don't have significant astigmatism, so that didn't really play into the decision that much.

 

Truth be told, I could have worked with either -1.0 or -1.5. The only downside to a stronger diopter is the reduced VF size (frame lines push out to the edge more in a magnified view)), but on 50mm, it still seems to give me plenty of space to work with.

 

~Dan

[jaapv]

The fault was factoring in the preset -0.5. If it were not the correct value for perfect eyesight, everybody with good eyes would need to use a + 0.50 diopter, which is of course illogical. So with your diopter and eye value you need to end up somewhere close to -0.50.

[Orient XI]

My excellent optometrist pointed out that spherical correction lenses are next to useless if you have more than slight astigmatism since you take both portrait and landscape shots. Obvious if you think about it.

[jaapv]

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That is well known. In that case you need the WalterrEyepiece diopter.

[Spiritualized67]

My optometrist pretty much said that all people have some degree of astigmatism - although mine seemed to be relatively minor.

 

I will say that my new diopter makes a huge huge difference. I pretty much can't focus without it. If you have any trouble seeing the rangefinder patch, I would whole heartedly recommend trying it out. For those with serious astigmatism, the Walter eyepiece seems like a good alternative, although it's somewhat bulky looking.

 

~Dan