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field flatteners- pros and cons? (1 Viewer)

pat mitchel

Active member
Is there anything that can be assumed when a product description of a roof prism binoculars states that it has a field flattener lens in the optics? Or is the nature of how and where the lens employed determine it's characteristics. The meade masterclass and celestron regal (recent releases) has it listed in their specifications. Thank You, Pat
 

Maljunulo

Well-known member
There is a lot of rather shrill carping criticism of flat field binoculars here, and arguments to the effect that they make the view somehow "artificial".

I like the entire field to be in focus at the same time, but I guess that's just me.
 

Gilmore Girl

Beth
Supporter
United States
Recently, I got to look through a Swaro EL 8x32. I have a Nikon Monarch HG 8x30 which has a field flattener in it and the view seems natural and never too flat or compressed to me. I wanted to see if I noticed anything different in the EL's flat field compared to the HG.
I paid particular attention to this. I'd say it appeared to have a somewhat slightly more 2D or flatter image than the HG, but I didn't have any issue with it and It didn't seem to look 'artificial' to my eyes. I decided it's a non-issue for me and it wouldn't ruin the fantastic view the EL provides. Sharp all the way to the field edge was what actually looked somewhat strange to me because I'm just not used to that. It was impressive to see such a huge area in focus.
 
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WJC

Well-known member
Is there anything that can be assumed when a product description of a roof prism binoculars states that it has a field flattener lens in the optics? Or is the nature of how and where the lens employed determine it's characteristics. The meade masterclass and celestron regal (recent releases) has it listed in their specifications. Thank You, Pat
I find very few things about getting older to be beneficial. However, sometimes age can give you to the maturity to know what is important and what is just fodder for useless conversations, wherein words in an ad can be elevated to reality ... whether they are or not. Several years ago, a rep for a major company—which shall remain nameless—showed me his new line of binoculars. With every few words, he would tell me about the binocular’s ASPHERICS, as if the WORD would force me into buying into the line.

1) I saw NO improvement over many less expensive binoculars I had in inventory.

2) 2 of the 4 samples had debris inside.

3) I decided to let him impress others with his ASPHERICS

ALPHA, vintage, Aspheric, or Flatfield are such words. The first two words are for newbies. The other 2 have their place. BUT ONLY IF TECHNICALLY ACCURATE! 'Anyone interested in an autofocus binocular?

Bill
 
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jring

Well-known member
Hi Denis,

but you are aware that the Fujinon has field flatteners too, right? As do the Nikon SE series to name some other porros with that technology.

Field flattener is the jargon term for a Smyths corrector which is designed to counteract an aberration called field curvature (the focal plane is not flat but curved - direction and amount depend on the telescope design - if the center is sharp and the edge is not but you can refocus so the edge is sharp and center is not, that's field curvature).

It has nothing to do with the 3d effect in porro binoculars which is caused by stereopsis and a wider stereo basis. There is another effect though, which allows depth perception even with monocular vision, that indeed is lost with field flatteners.

Joachim
 
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[email protected]

Well-known member
Supporter
Hi Denis,

but you are aware that the Fujinon has field flatteners too, right? As do the Nikon SE series to name some other porros with that technology.

Field flattener is the jargon term for a Smyths corrector which is designed to counteract an aberration called field curvature (the focal plane is not flat but curved - direction and amount depend on the telescope design - if the center is sharp and the edge is not but you can refocus so the edge is sharp and center is not, that's field curvature).

It has nothing to do with the 3d effect in porro binoculars which is caused by stereopsis and a wider stereo basis. There is another effect though, which allows depth perception even with monocular vision, that indeed is lost with field flatteners.

Joachim
Your correct and what I like is the 3D effect in Porro prism binoculars which is as you say different from the flat field produced by field flatteners. The Fujinon FMTR-SX does use field flatteners because it has some of the sharpest edges I have ever seen. The edges are even sharper than the Swarovski EL which had the sharpest edges I have seen before the Fujinon. 3D or stereoscopic effect, Depth of Field and Field Flatteners are all different but in a way related.
 

Brink

Well-known member
I think it is probably just a sales tactic in many cases. I have a Monarch HG that has a "field-flattener system" or some such, but it shows plenty of field curvature to my eyes.
 

WJC

Well-known member
Gary,

Does the FMTR-SX have a field flattener? I've been inside many and think that would have been an important thing to have forgotten. But before my test, I did assume the Prostar was better off-axis.

BC
 

quincy88

Well-known member
I think it is probably just a sales tactic in many cases. I have a Monarch HG that has a "field-flattener system" or some such, but it shows plenty of field curvature to my eyes.
I'm starting to think the same thing. Just a buzzword that has lost whatever technical definition it used to have (if any). Like "HD lenses," I'm not convinced that in marketing terms it actually means anything. Made with "real cheese," you know?
 

WJC

Well-known member
I thought that was what the "F" in FMTR-SX stood for.

Wasn't the predecessor just the MTR-SX?
Right you are. IT's a great binocular! I was just referring to having a separate field flattening lens. Many roads can lead to that destination. By the way, the FMTR-SX did NOT replace the MTR-SX. It was just another in the line.

Bill
 

[email protected]

Well-known member
Supporter
I think it is probably just a sales tactic in many cases. I have a Monarch HG that has a "field-flattener system" or some such, but it shows plenty of field curvature to my eyes.
Allbinos commented also on the field curvature in the Nikon Monarch HG. It doesn't seem like it even has a field flattener. The Fujinon FMTR-SX 10x50 and 7x50 have some of the sharpest edges I have seen in binoculars, so their field flattener is very effective.
 

Maljunulo

Well-known member
Thank for the correction. I have no recollection of what they were called, so I guessed.

I had a pair of the predecessor in 10X70 and gave them to a son-in-law when I replaced them with the newer FMTR-SX, also 10X70.

What were they called?
 
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[email protected]

Well-known member
Supporter
I thought that was what the "F" in FMTR-SX stood for.

Wasn't the predecessor just the MTR-SX?
Maybe you were right. Fujinon did make the MTR-SX Poseidon SX. It seems to be discontinued.

 

tenex

reality-based
No. It means "flat field." "Field flattener" means another lens or lenses.
This is a good point worth expanding upon for the OP. Some "flat field" or even "field flattener" models are flatter than others, depending on implementation, so you can only tell by trying or searching online forums. In my opinion it's unnecessary to eliminate field curvature entirely, and even Smyth correctors leave small residual effects that some here notice. A large area of true sharpness transitioning smoothly to a still usably sharp periphery can be achieved without field-flattener lenses, seems more natural to many, and is my personal preference.
 
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Maljunulo

Well-known member
A large area of true sharpness transitioning smoothly to a still usably sharp periphery can be achieved without field-flattener lenses, seems more natural to many, and is my personal preference.
How?

Not doubting you, trying to learn.
 

[email protected]

Well-known member
Supporter
This is a good point worth expanding upon for the OP. Some "flat field" or even "field flattener" models are flatter than others, depending on implementation, so you can only tell by trying or searching online forums. In my opinion it's unnecessary to eliminate field curvature entirely, and even Smyth correctors leave small residual effects that some here notice. A large area of true sharpness transitioning smoothly to a still usably sharp periphery can be achieved without field-flattener lenses, seems more natural to many, and is my personal preference.
There are some binoculars that use field flatteners that don't have the residual effects like the Zeiss SF. Nikon EDG, Nikon Monarch HG, Canon 10x42 IS-L and Fujinon FMTR-SX. The Swarovski EL is the worst with a noticeable "Absam Ring" towards the edge which disappears at the edge. The new Swarovski NL has a smaller but noticeable "Absam Ring".
 

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