Is image black-out normal?

[mattpau]

I have a Bushnell Spacemaster 60mm with ED glass and a little 22x wide angle eyepiece. With this scope I get a nice stable image if my eye is anywhere remotely close to the ideal position. I find looking through this scope very comfortable.

More expensive scopes deliver a brighter, crisper image (with more "wow factor"), so I decided to upgrade to the Zeiss 65mm Diascope with the zoom lens (15-45x on the 65mm). This scope has many idiosyncracies that I'm not particularly fond of, but one of the most annoying is the tendency of the image to "black out" if my eye is not in the perfect position. A consequence of this is that it's virtually impossible to digiscope hand-held: it's simply too difficult to hold the camera steady in the ideal position. All or part of the photos tend to be blacked out.

I have noticed this "blacking out" phenomenon with other optics. Is it normal? Or does it indicate a problem with the equipment? Thanks for any info.

[raymondjohn]

Dear Paul

I have the same setup you have and don't have much of a problem with blackouts. However if I get a little to excited when seeing a new bird then blackouts do happen.
I find that not setting up the tripod correctly is the reason I get the most blackouts.
Best wishes
raymondjohn

[iporali]

...one of the most annoying is the tendency of the image to "black out" if my eye is not in the perfect position. A consequence of this is that it's virtually impossible to digiscope hand-held: it's simply too difficult to hold the camera steady in the ideal position. All or part of the photos tend to be blacked out.

I have noticed this "blacking out" phenomenon with other optics. Is it normal? Or does it indicate a problem with the equipment? Thanks for any info.
Paul,

Blacking-out is simply a symptom of too much eye-relief. It appears when the iris of the eye casts a shadow on the retina (or a camera diaphragm on the sensor/film). You see it more often in bright light, with bright, wide-angled optics and with large exit pupils (low powers/large objectives) - ironically often with very high-quality optics. It is really annoying, but it can be fixed by keeping the eye (or the camera) far enough from the eyepiece. If your previous scope has had a very low eye-relief, it may be difficult to break the old habit to push the eye against the eyepiece.

Digiscoping on the other hand should be easily fixed. You can try if it is any easier to digiscope by zooming the scope to, say, 18-20x power (which reduces the eye-relief). You could also make a simple centering/extension adapter from any plastic tube (someone used a pill-tube) which fits between the camera and the eyepiece. Most cameras however need all the ER that the eyepiece can deliver.

If you are further interested in this phenomenon, in astro-optics discussions it is often called a "kidney bean effect".

Regards,

Ilkka

[Anthony Martin]

I have a Bushnell Spacemaster 60mm with ED glass and a little 22x wide angle eyepiece. With this scope I get a nice stable image if my eye is anywhere remotely close to the ideal position. I find looking through this scope very comfortable.

More expensive scopes deliver a brighter, crisper image (with more "wow factor"), so I decided to upgrade to the Zeiss 65mm Diascope with the zoom lens (15-45x on the 65mm). This scope has many idiosyncracies that I'm not particularly fond of, but one of the most annoying is the tendency of the image to "black out" if my eye is not in the perfect position. A consequence of this is that it's virtually impossible to digiscope hand-held: it's simply too difficult to hold the camera steady in the ideal position. All or part of the photos tend to be blacked out.

I have noticed this "blacking out" phenomenon with other optics. Is it normal? Or does it indicate a problem with the equipment? Thanks for any info.

Hello Paul.

Whilst using the Zeiss, be sure to extend the twist up eyecup and this should put your eye at the optimum distance from the lens element. As already explained, the condition is more prevalent in top quality scopes such as the Zeiss, but it is simply a result of the long eye relief, (the distance from the eyepiece lens which gives the full image) offered by such equipment.
You should gradually get used to this effect and eventually find it much more relaxing on the eye.

Tony.

[mattpau]

Thank you very much for these replies. I am happy to learn what causes black-out - I certainly never would have guessed that it's the shadow of my iris!

I guess I will have to keep trying to get used to the Zeiss. My recollection is indeed that black-out tended to occur particularly with very expensive optical equipment. My impression is that the image of the Bushnell NEVER blacks out. The eyepiece has no eyecup - one holds one's eye very close to the lens. If I move my eye further away I get more of a tunnel effect. All this does indeed point to short eye relief.

Ilkka, could you expand on your statement that "most cameras however need all the ER that the eyepiece can deliver"? Despite the short eye relief, there appears to be no problem digiscoping hand-held with the Bushnell, unlike with the Zeiss. Another problem with the Zeiss, I have to admit, is that the eyepiece is so big that if one rests the edge of the camera lens on it, the latter will touch the eyepiece's glass, which I can't imagine is good. On the Bushnell, the edge of the camera lens rests on the plastic surrounding the glass of the much smaller eyepiece.

[iporali]

Ilkka, could you expand on your statement that "most cameras however need all the ER that the eyepiece can deliver"? Despite the short eye relief, there appears to be no problem digiscoping hand-held with the Bushnell, unlike with the Zeiss. Another problem with the Zeiss, I have to admit, is that the eyepiece is so big that if one rests the edge of the camera lens on it, the latter will touch the eyepiece's glass, which I can't imagine is good. On the Bushnell, the edge of the camera lens rests on the plastic surrounding the glass of the much smaller eyepiece.
Paul,

I meant similar blacking-out with the camera as with the eyes, but this is actually quite uncommon with the cameras.

Most of the popular digiscoping cameras (Nikon Coolpixes, Canon A-series, Contax/Kyocera) to my knowledge need something like 16-20mm eye-relief to produce unvignetted images (many larger cameras even more). For a digicamera to black-out in digiscoping, the ER of the eyepiece must exceed the "entrance-pupil distance" of the camera. Not many scope eyepieces have that much ER - the only cases I have seen a camera to black-out, have been a small Canon Ixus on my Swaro zoom (18mm ER) and a Canon A80 on a Leica 32xWA (20mm ER). The Zeiss zoom should have less ER than both the above mentioned, which means that it is more prone to vignetting than blacking-out - but in any case it is very sensitive for careful centering. If you could use some kind of adapter/centering device, you should be able to bring the camera almost to a contact with the eyepiece and see a much wider field on the camera than with your Bushnell.

I am sorry if I confused more than I clarified, but I can try again later if necessary. ;)

Ilkka

[mattpau]

Paul,

I meant similar blacking-out with the camera as with the eyes, but this is actually quite uncommon with the cameras.

Most of the popular digiscoping cameras (Nikon Coolpixes, Canon A-series, Contax/Kyocera) to my knowledge need something like 16-20mm eye-relief to produce unvignetted images (many larger cameras even more). For a digicamera to black-out in digiscoping, the ER of the eyepiece must exceed the "entrance-pupil distance" of the camera. Not many scope eyepieces have that much ER - the only cases I have seen a camera to black-out, have been a small Canon Ixus on my Swaro zoom (18mm ER) and a Canon A80 on a Leica 32xWA (20mm ER). The Zeiss zoom should have less ER than both the above mentioned, which means that it is more prone to vignetting than blacking-out - but in any case it is very sensitive for careful centering. If you could use some kind of adapter/centering device, you should be able to bring the camera almost to a contact with the eyepiece and see a much wider field on the camera than with your Bushnell.

I am sorry if I confused more than I clarified, but I can try again later if necessary. ;)

Ilkka

Thanks Ilkka.

I'm now beginning to believe that the blackout with the Zeiss I've been talking about is NOT due to long eye relief. I don't have the scope here at work, but my recollection is that there isn't that much of a problem of black-out when moving my eye forward and back, although if I get very close it will occur. The problem occurs more because of side to side movement of the eye, which you seem to allude to: "but in any case it is very sensitive for careful centering". I don't know if this black-out is still caused by the iris creating a shadow when someone is looking through the scope, but it definitely also occurs when trying to digiscope hand-held, making the activity almost impossible without some kind of extra equipement, such as an adapter, which I don't have at present.

I should mention that, although I haven't digiscoped very much, it's now become instinctive to increase the optical zoom, otherwise I do indeed get vignetting with the Bushnell. I don't know if it's worse than with the Zeiss - presumably it is since the Bushnell's eye relief definitely seems low, but I haven't checked. With the Zeiss it's hard to get any kind of picture at all!

I naively thought that by spending a fair bit of money, everything would be easier with the new scope. Clearly not so. It's frustrating.

[iporali]

Thanks Ilkka.

I'm now beginning to believe that the blackout with the Zeiss I've been talking about is NOT due to long eye relief. I don't have the scope here at work, but my recollection is that there isn't that much of a problem of black-out when moving my eye forward and back, although if I get very close it will occur. The problem occurs more because of side to side movement of the eye, which you seem to allude to: "but in any case it is very sensitive for careful centering". I don't know if this black-out is still caused by the iris creating a shadow when someone is looking through the scope, but it definitely also occurs when trying to digiscope hand-held, making the activity almost impossible without some kind of extra equipement, such as an adapter, which I don't have at present.
Actually I think the blackout in your eyes IS due to long eye relief (sorry for the confusion) - it happens exactly when you move the eye side-to-side *at close distance* and this is quite common. With a camera this is also possible but only in some special cases. If you hand-hold the camera trying to keep it from scratching the eyepiece, it is simply very difficult to center - and this may produce very similar looking blackouts. Fortunately this is easily prevented with a simple centering ring, which can be made from eg. a piece of (<1cm thick semi-soft) packaging cell-foam.


I should mention that, although I haven't digiscoped very much, it's now become instinctive to increase the optical zoom, otherwise I do indeed get vignetting with the Bushnell. I don't know if it's worse than with the Zeiss - presumably it is since the Bushnell's eye relief definitely seems low, but I haven't checked. With the Zeiss it's hard to get any kind of picture at all!

I naively thought that by spending a fair bit of money, everything would be easier with the new scope. Clearly not so. It's frustrating.
I am sure everything IS easier and better with the Zeiss - you just need a centering device on the eyepiece, where you can support the camera and get it close enough. I also think you can eventually adjust your viewing so that your eye does NOT come too close - you might even want to sacrifice some field-of-view to avoid blackouts.

Good luck :t:

Ilkka

[mattpau]

Thanks Ilkka and sorry for my delay in responding. So if I understand correctly, this "centering ring" would be placed on the scope's eyepiece. Is the goal to have it there permanently, or only when taking a picture? Sorry if I'm being dumb, but I'm having a lot of trouble visualizing this, let alone actually making it!

[iporali]

Thanks Ilkka and sorry for my delay in responding. So if I understand correctly, this "centering ring" would be placed on the scope's eyepiece. Is the goal to have it there permanently, or only when taking a picture? Sorry if I'm being dumb, but I'm having a lot of trouble visualizing this, let alone actually making it!
No problem Paul, my Finnish friends often struggle with my explanations ;)
But yes, that was my idea about the simplest possible "adapter". Just cut a "ring" which fits inside the eyepiece's eyecup and the size of the open center fits to the camera objective. This could be made from a variety of materials, eg soft foams which can be easily cut with scissors. But of course a *much* better solution would be a commercial digiscoping adapter (see eg. http://www.spidertech.fi/ or http://www.at-infocus.co.uk/digiscoping.html).

Ilkka

[mattpau]

HI Ilkka

Thanks a lot for your explanation and, again, apologies for the delay in responding. I was hoping I'd actually have given this a try by the time I got back to you but haven't got around to it yet. On the weekend, though, I did take the Zeiss out birding with me - I'd reverted to my Spacemaster for the past several weekends.

The very fine quality of the Zeiss image did strike me, but the blacking-out remains annoying. I found a snowy owl and couldn't get a proper digiscoping image with my camera. (Then the camera battery died - typical!) But the biggest problem with the Zeiss is trying to look comfortably through the very large eyepiece. I just can't seem to do it - I have to cock my head at an unnatural angle that gives me quite severe neck ache. I wrote about this in another thread, to which you helpfully responded.

I don't see how I can keep this scope. I hope I can sell it to someone who will enjoy it. I'm not giving up, though, on obtaining a high-quality scope I can live with. I'd like a scope more like the Bushnell, ie less blackout, smaller and more compact and a smaller eyepiece than the Zeiss, but a better image than the Bushnell and also water and fog-proof. Any suggestions? Thanks.

[iporali]

Thanks Paul - and sorry to hear that such a fine instrument does not seem to work for you so well. I'd recommend you to take a good look at Kowa offerings (eg. TSN603 or 663) - they seem to have an interesting 20-40x zoom, which looks even narrower than their 20-60x version (which itself is narrower than most others). Also some of the fixed eyepieces (excellent IMHO) are much smaller.

It is interesting that many eyepieces have become wider in recent years. Eg. Swarovski AT80 zoom originally was long and narrow, but the last two revisions have been shorter and wider. The same seems to have happened with the newer Kowa TSN823 zoom. Maybe it is due to increased eye-relief and wider field-of-view?

Best of luck,

Ilkka

[mattpau]

Thanks a lot Ilkka. I will perhaps try the Zeiss a little while longer, but look into getting a Kowa. Kowas are quite common around here, but one virtually never sees a Zeiss. I see that someone else from Canada is trying to sell exactly the same model of Zeiss as mine on Bird Forum. However, as his is unused, I assume he's not offering it for sale because he's disssatisfied with it!

All the best
Paul