7x50 porros for dusk viewing? (1 Viewer)

[matt green]

Greetings!

Recently been pondering wether a budget priced 7x50 porro would have any major advantages at dusk compared to my regular hawk ed x 10x42, had a brief look from various sites on the web but can't find any twillight factors etc. I have a particular interest in owls and curious if investing in a 7x50/7x42 for the sole purpose of those winter 'stake outs' would be worthwhile!

Could they even have an advantage over any of the alpha bins of 8x42/10x42 configurations solely for peering into dark hedgerows at dusk?

The models I have in mind are the nikon action ex 7x50 and opticron imagic tga 7x50.

Thoughts welcomed,

Matt

 

[Ian Byrnes]

Hello Matt
Having used the Aculon 10x50 in the past (not the Action...which are sharper) the dawn and twighlight vision was slightly brighter than my 8x42 Vanguard EDII but not as good as my 10x42 Zeiss Conquest. In my opinion the weight & ergonomics of porros make them less comfortable and pleasing to use. 7's though will add an extra brightness and you can get some real bargains on Nikon porros at the moment. So.....yet again it's your call.
Ian

 

[Ian Byrnes]

By the way.... Beautiful photography.....
you might like the work of a mate of mine www.kenorton.com in Florida. He does realistic oils of similar subjects.
Regards. Ian

 

[matt green]

Thanks for your insight, Ian

Yes folks on here do seem to favour the actions over the aculons, they do come up secondhand every now and then so will keep a look out..will likely try a pair out next time I'm near cleyspy on the coast.

Thanks re the photography, love the vintage bottles from your link. Spent many happy hour of my childhood digging such things up out of Victorian waste dumps!!

Matt

 

[Dennis Mau]

Matt. You would be better off with a Nikon 10x50 porro for seeing detail at night which would have a 22.4 Twilight Factor. The 7x50 would only have an 18.7 Twilight Factor. The 10x42 would better than a 7x50.

"Twilight Factor
Twilight factor is a theoretical estimation of how much detail can be seen in low light and is estimated by first multiplying the magnification by the objective lens size, and then taking the square root of that product. So twilight factor can increase with an increase of either magnification and objective lens size or both. The twilight factor can also remain the same if the magnification is doubled but the objective size is cut in half (and vice versa).For example, the 8 X 50 binoculars would be 8 times 50 =400, then the square root of 500 = 20.0 value for twilight factor. The twilight factor for the 10 X 50 is simply 10 times 50 = 500 and the the square root of 500 = 22.4, so the 10 X 50s have a 12% detail advantage over the 8 X 50s in low light. In table 2, the twilight factor has been calculated for several sizes of binoculars. I also included the ratio of each value to the 12 x 50 binoculars for comparison. You will notice that as magnification decreases and as the objective lens becomes smaller, the twilight factor decrease as detail is lost. In the table, the 12 x 50s will show the most detail in low light and the 8 x 32s will have the least detail."

Table 2. Twilight Factor Calculations for Common Binocular Sizes
Mag. & Objective Equation Twilight Factor Rel. to 12×50
8 x 50 sq. root (8 x 50) = 20.0 0.82
10 x 50 sq. root (10 x 50) = 22.4 0.91
12 x 50 sq. root (12 x 50) = 24.5 1.00
8 x 42 sq. root (8 x 42) = 18.3 0.75
10 x 42 sq. root (10 x 42) = 20.5 0.84
8 x 32 sq. root (8 x 32) = 16.0 0.65
10 x 32 sq. root (10 x 42) = 17.9 0.73

 

[Hermann]

Matt. You would be better off with a Nikon 10x50 porro for seeing detail at night which would have a 22.4 Twilight Factor. The 7x50 would only have an 18.7 Twilight Factor. The 10x42 would better than a 7x50.

Dennis:

That's the theory. Works beautifully as long as both binoculars are tripod mounted. Things may be somewhat different when handheld, since the handshake does cost you quite a bit of resolution in the 10x50. Plus the depth of field of a 7x42/50 is far larger, that helps at dusk quite a bit, too.

Problems are rarely so simple that they can be solved by quoting some unidentified source.

Hermann

 

[wdc]

Dennis:


Problems are rarely so simple that they can be solved by quoting some unidentified source.

Hermann

:t:

Thank you for pointing this out.

 

[jring]

Hi Hermann,

I agree that this result is without a provision for the increasing loss of detail with higher magnification due to the user's inability to hold the instrument steady.

But this formula is derived in chapter 11 of Albert Koenig & Horst Koehler, Die Fernrohre und Entfernungsmesser... so while Dennis might have failed to identify the source, it's hardly an obscure one...

Joachim

 

[Hermann]

I agree that this result is without a provision for the increasing loss of detail with higher magnification due to the user's inability to hold the instrument steady.

But this formula is derived in chapter 11 of Albert Koenig & Horst Koehler, Die Fernrohre und Entfernungsmesser... so while Dennis might have failed to identify the source, it's hardly an obscure one...

I know the source ... That's one of my essential reference books on binoculars as well.

However, König/Köhler (and later also Leinhos) did not take into account handshake and so on - they looked at what you can see through binoculars mounted on a tripod. In real life things are quite different.

So in theory Dennis was right. He even quoted the right source (even though he didn't identify it). But in real life there are other aspects that need to be taken into account - unless you only use the binoculars on a tripod.

Hermann

 

[matt green]

Thanks for the replies everyone,

Interesting thoughts regarding the 10x50, I lately I have come to prefer the view through 10x binos.

I see swarovski make the slc with a stonking 56 objective, they look a bit weighty though and priced well over what I would consider paying for a occaisonal use only binocular!

Matt

 

[Rico70]

hey Jimi, Opticron is just as good.

But Swaro is on another level!

 

[Rico70]

However, König/Köhler (and later also Leinhos) did not take into account handshake and so on - they looked at what you can see through binoculars mounted on a tripod. In real life things are quite different.

So in theory Dennis was right. He even quoted the right source (even though he didn't identify it). But in real life there are other aspects that need to be taken into account - unless you only use the binoculars on a tripod.

Hi Hermann, see if this can interest you too.

https://www.birdforum.net/showthread.php?t=384516

 

[Dennis Mau]

Thanks for the replies everyone,

Interesting thoughts regarding the 10x50, I lately I have come to prefer the view through 10x binos.

I see swarovski make the slc with a stonking 56 objective, they look a bit weighty though and priced well over what I would consider paying for a occaisonal use only binocular!

Matt

In low light 10x50's, 12x50's, 8x56's and 10x56's are really good performers. Especially those with good transmissions like the Steiner Night Hunter, Swarovski SLC or SV, Zeiss FL's and Zeiss Conquest's. Herman is correct though that the higher magnification's are harder to hold steady so you are going to lose some resolution, FOV and DOF with them. If you want something that is really good for Owls try an 8x56 or 10x56. Although the 10x56 would in theory show more detail than the 8x56 you might like the 8x56 better for the steadier view, bigger FOV and better DOF. For my low light use I use a Zeiss Conquest HD 8x56 that I picked up for pretty cheap. It is good for tracking Owls because Owls are quick and hard to spot and it has a reasonably large FOV and it is very bright having AK prisms. A good 8x56 will almost seem like it self illuminates or the view through the binocular seems brighter than your eyes although in theory that is not true. Another good Owling binocular is the Zeiss Night Owl(No Pun Intended). Here is a nice pair on Ebay for $1150.00. They would be very good for Owls also. Also, here is a nice pair of Swarovski SLC 8x50's which would be great for Owling. Here are a couple pictures of a lady from a Raptor Club that was in the airport at Jackson Hole Wyoming when I was coming back from Yellowstone National Park that had one of the heaviest Owls around(Eurasian Eagle Owl) that can actually take down animals the size of a Deer!

https://www.ebay.com/itm/ZEISS-8-x-...843455?hash=item2f3acaf8ff:g:274AAOSwB19cBUyT
https://www.ebay.com/itm/Swarovski-...752048?hash=item2f357b8bb0:g:04gAAOSwmkBcDqhw
http://www.oregonphotos.com/Astro-binocular-reviews-BJ.html

 

[Rico70]

coerenza alternata

I use a Zeiss Conquest HD 8x56 that ... it has a reasonably large FOV

Hi Dannis, but until 5 days ago you said exactly the opposite. This for you was the too narrow view with the "tunnel effect"!

I'm wondering if the amplitude could change based on the brand or the fact that you bought it? o




Of course I'm kidding! .. and it's always fun to read you.

 

[Cyclops]

Looking at that table, it doesn't make sense that a 10*50 would be brighter than an 8*50! Surely its the other way around. Also anyone know how you calculate the square root of a number on a basic calculator?

 

[Binastro]

Cyclops.
Without using the proper formula for square roots, just guess.

Say one wants the square root of 22.1.
4x4=16
5x5=25.

So it is likely to be nearer 5 than 4.

I would guess 4.7.
Using the calculator 4.7x= is 22.09.
so try 4.71x= 22.18
so try 4.701x= 22.099

4.701 is more accurate than needed. I would just say 4.7 in this case.

B.

 

[Dennis Mau]

Looking at that table, it doesn't make sense that a 10*50 would be brighter than an 8*50! Surely its the other way around. Also anyone know how you calculate the square root of a number on a basic calculator?

Twilight Factor is NOT the same as brightness. Twilight Factor means you can see more detail in low light because of the higher magnification. The 8x50 would be brighter because of the bigger exit pupil if your pupils dilated wide enough to take advantage of it but you would see more detail in low light with the 10x50.

 

[Dennis Mau]

Hi Dannis, but until 5 days ago you said exactly the opposite. This for you was the too narrow view with the "tunnel effect"!

I'm wondering if the amplitude could change based on the brand or the fact that you bought it? o




Of course I'm kidding! .. and it's always fun to read you.

The Zeiss Conquest does have a reasonably large FOV for an 8x56 AT 377 Feet. The size of the FOV is relative to the format you are talking about. The 8x56's with the very biggest FOV like the SLC and FL are only 400 feet.

 

[Rico70]

The Zeiss Conquest does have a reasonably large FOV for an 8x56. The size of the FOV is relative to the format you are talking about. The 8x56's with the very biggest FOV like the SLC and FL are 400 feet. The Trac Toric 10x50 was only 304 feet which is pretty narrow

Both the tunnel effect and the adjective of narrow and wide vision are determined by the apparent width of the observation window (not by the format). If you want to tell yourself lies, you are free to do it, but it is not what you say.

The tunnel effect is given by a narrower than normal field of view, but both the Toric and the Zeiss mentioned both have a normal field of view. So with the exact same width of the observation window.

How can you say that one has a narrow vision and a tunnel effect, while the other has a reasonably wide vision?

Do you understand that what you say is a paradox?

 

[Rico70]

Looking at that table, it doesn't make sense that a 10*50 would be brighter than an 8*50! Surely its the other way around.

And in fact it is as you say, but only in the twilight.
8x50 is brighter than 10x50, because 8x50 is as bright as 10x56.
But then, in the moonlight and darker, both 10x will be more detailed and preferable, for that low light.

See how it works here
https://www.birdforum.net/showthread.php?t=384516