Nikon Monarch 7 8x30 edge sharpness/focus question (1 Viewer)

Hello everyone!

I am a happy owner of a brand new M7 8x30. I love the form factor and the quality at the price point. Seems like a lovely piece of gear in many respects.

I do, however, have a concern that I'd like some insight in. Therefore I am humbly tapping into the collective intelligence of this forum. Hope you can help.

---> The issue I have is this: while focusing on a subject the center of the image is nice and crisp. The edges much less so. Seems like the bottom of the image circle exhibits blur closer to the center than other parts of the image circle.

---> By altering the focus I can make the edges truly sharp and in focus. But then I lose the central sharpness. Is this a case of pronounced field curvature or something similar?

---> Does your M7 8x30 exhibit this? Should I send my pair to be adjusted under warranty?

I own a cheaper Action EX 7x50 and it does not have this issue. Neither did I notice that in the pair of prostaff 8x30 that I tried (although briefly). Is this a characteristic of the wide FOV that the M7 8x30 has?

I'm pretty experienced in camera optics but much less so in binoculars so any help is truly appreciated. I'd rather not send the pair to be serviced unless it is certain there is something wrong with them.

(ps. I did use search but could not find definitive discussion on this, thanks again for all helpful comments :t

You are right about field curvature.

Remember, if you have a binocular with a wide angle of view it's going to become more apparent than with one with a very narrow angle of view like the Action EX 7x50, which is only 6.4 degrees. A binocular like the expensive Nikon 7x50 SP has a field flattener Mencius lens reducing field curvature almost entirely.

Eye placement will also be more critical on the M7 8x30 because of the smaller exit pupil.

The Action EX 7x50 has an aspheric element in the ocular which reduces pincushion distortion at the edges. This along with the narrow field of view and relatively low magnification does give an illusion of remarkably well corrected optic for the money. The Nikon Action EX 7x35, on the other hand, has a massive FOV of 9.3 degrees. Good for tracking action but of course it's blurred away from the centre.

An example of a fully corrected binocular would be the Swarovski EL 8.5 x 42 which is massively expensive !
http://www.allbinos.com/251-binoculars_review-Swarovski_EL_8.5x42_Swarovision.html

Hi Subhelic, :hi:

Welcome to Bird Forum!

It is a matter of field curvature. My Monarch 7 8x30 shows the same effect.

If you place the edge of your view up against a vertical object like a telephone pole or the vertical edge of a building you should see a significant bending or "pincushioning" effect on the pole or the building edge which will be out of focus. You can dial the edge into focus but when you do this you will lose your sharp focus in the center of the view.

This is normal in many binoculars that have a wide FOVs like your Monarch 7 8x30 which is a Roof Prism binocular. It is also seen in Nikon's iconic 8x30 EII Porro prism binocular which shows probably the best example of this "pincushioning."

Bob

Tervetuloa.
Rare form of halo. (Subhelic arc).

Many binoculars exhibit different sharpness depending on the position angle.
This is I think because of the prism chain.
Without prisms one would expect the same performance at any position angle unless the optics were misaligned or tilted a bit.

The aspheric elements in the Nikon Action VII eyepieces show to me a wavy undulating change in magnification if I look carefully.

I have not looked through a Monarch 7 although I have looked through the Monarch HG.

I think what you see is all "normal". In my experience the bottom of the field typically looks less sharp because the eyeball naturally rotates down in a way that introduces less vignetting of the field edge than when it rotates to the side. The extra vignetting at 3:00 and 9:00 acts as an aperture stop that reduces the field edge aberrations in those directions. An asymmetry in the instrument's off axis corrections can be tested by simply rotating the binocular in front of one eye to see if the asymmetry rotates with the binocular

BTW, field curvature has nothing to do with bending telephone poles at the edge of the field. The bending of straight lines toward the edge is caused by one of the rectilinear distortions: pincushion or barrel. Field curvature only causes defocus toward the edge. Telephone poles defocused by field curvature remain perfectly straight

My M7 exhibits exactly the same characteristics, so you don't have a 'problem' one. Without hitting the optical science too much, Nikon have obviously balanced out criteria here to create a compact, lightweight, bright set of bins with an outstanding field of view without loading it with field flatteners and other lenses that would have made it more expensive/heavier/larger. Thus it is an outstanding piece of kit for the money!

Hi everybody and thanks for the warm welcome! :hi:

And thanks for the wealth of information & experience you shared! This is genuinely helpful: now I know I do not have a lemon but simply an instrument that exhibits some of the compromises necessary to produce a small, bright, wide FOV binocular.

Ah, gotta love optics. No free lunch to be had. I suppose a field flattener would indeed have made it darker/bigger and more expensive. Even though the periphery of the image circle is somewhat lost to blurrines it still helps tracking and makes the viewing experience less tunnel like.

I tried holding the binoculars upside down to see whether it had an effect on the blurriness of the bottom part of the image. To my surprise the effect remained unchanged! So it truly was an effect of the eye - ocular geometry! Fascinating! My subjective experience was that my pupils were perfectly aligned with the oculars. :eek!:

I also experimented with various positions of the ocular, uhh, what's the word... the extending ocular rubber cushions that have three positions where they click in place. The first click seems to work best for me. Nice, wide FOV, wow!

And boy do I love the form factor... these are so small, yet quite capable! So easy to just slip in the camera bag! On my way to work I stopped to observe two swans who leisurely had breakfast in the field. At that point I completely forgot about the field curvature issue and just enjoyed the magnificent view. Love these things! :t:

* * *

EDIT: The allbinos review also notices this issue

http://www.allbinos.com/272-binoculars_review-Nikon_Monarch_7_8x30.html

So, I'm not sending my copy to be serviced. Maybe I'll try and find another pair to do some comparisons with but it seems my binos are well within spec.

Binastro said:

Tervetuloa.
Rare form of halo. (Subhelic arc).

Click to expand...

Kiitos! ||

And indeed you are correct about the halo. :t:

One thing i forgot to mention - despite not wearing glasses, i've started using the M7 with the eyecups fully down, holding them in front of my eyes (and beyond any credible imagined 'eye relief'). It took me a while to get used to, and these are the only bins i perform this trick with, but i certainly appreciate the view! It also seems a lot more forgiving of some of the foibles referred to in a number of threads regarding these. It may not work for you, but perhaps have a go. I've no idea what's going on from a scientific point of view (nor really need to), but the whole vignetting/glare issue seemed to vanish and the view opened out even further.

paddy7 said:

One thing i forgot to mention - despite not wearing glasses, i've started using the M7 with the eyecups fully down, holding them in front of my eyes (and beyond any credible imagined 'eye relief'). It took me a while to get used to, and these are the only bins i perform this trick with, but i certainly appreciate the view! It also seems a lot more forgiving of some of the foibles referred to in a number of threads regarding these. It may not work for you, but perhaps have a go. I've no idea what's going on from a scientific point of view (nor really need to), but the whole vignetting/glare issue seemed to vanish and the view opened out even further.

Click to expand...

Thanks for the tip! I'll be sure to try this out. Maybe I'll see a couple of cranes on my way home. Yesterday they were there and I enjoyed watching them through the little Monarch binos. :t:

I also noticed how pleasant the view with the Monarchs was when I did not tilt my head forward (at all) but kept it straight and lifted the binos up to my eye. Seems like it's easier to align the pupils with the oculars that way.

paddy7 said:

One thing i forgot to mention - despite not wearing glasses, i've started using the M7 with the eyecups fully down, holding them in front of my eyes (and beyond any credible imagined 'eye relief'). It took me a while to get used to, and these are the only bins i perform this trick with, but i certainly appreciate the view! It also seems a lot more forgiving of some of the foibles referred to in a number of threads regarding these. It may not work for you, but perhaps have a go. I've no idea what's going on from a scientific point of view (nor really need to), but the whole vignetting/glare issue seemed to vanish and the view opened out even further.

Click to expand...

I think you would notice a similar positive effect on the vignetting if the current eye relief of the eye cups was longer.

When I use my 8x30 Monarch 7 I brace its eye cups up against and just under my eyebrows. If I move the eye cups back closer to my eyes I notice more vignetting the further I move them back. Especially when I roll my eyes side to side.

Some people have placed "O" rings in the ends of the eye cups to extend the eye relief. That has been discussed in this binocular forum.

Bob

ceasar said:

I think you would notice a similar positive effect on the vignetting if the current eye relief of the eye cups was longer.

When I use my 8x30 Monarch 7 I brace its eye cups up against and just under my eyebrows. If I move the eye cups back closer to my eyes I notice more vignetting the further I move them back. Especially when I roll my eyes side to side.

Some people have placed "O" rings in the ends of the eye cups to extend the eye relief. That has been discussed in this binocular forum.

Bob

Click to expand...

I think that's exactly it. I've never felt the eye relief is sufficient on these. In view of many other threads in the past concerning veiling glare and vignetting, i spent many a trip experimenting with them, as i felt that when i found the technique, these would be a valuable addition to the optics armoury. This has been my solution, but i'm aware that all faces are different (otherwise we'd save a lot of time in naming babies). I've assumed with many bins that cos i don't wear glasses, the eyecups should be fully extended, but this is often not the case. I use my FL 8x32s on one step-down on the cups now, and get a much fuller view as a result.
The trick with the eyecups-down technique is to find a way to keep the bins directly in front of your eyes, but that doesn't take long.

Been using mine for a while now and I'm still very pleased with the purchase. These things are so light, small and convenient to take with me just in case. The eyecups seem to work well in the first or second position. Fully extended they seem to rob some of the FOV. Thanks again everybody!