46 replies to this topic

[lighttrap]

Kenny, I remember that dialogue well. Ever since then, I've had a whole set of the 1951 USAF test charts on my desk. You can print them out from this site: Medium Format lens testing

I still find the use of colored supermarket flyers to be quite valuable in comparing color separation of various optics. It's interesting to me to see how my perception of various binos changes when I do detailed comparisons between different models. Some optics that seem OK, can occassionally offer up some real surprises when examined with a critical eye under controled conditions.

Mike

[EdZ]

gentlemen,

with regard to resolution testing charts:

keep in mind, values for any particular binocular for limit of resolution obtained by using a lens resolution line chart are only comparable to other binoculars values obtained from the same types of charts. they are not comparable to scotoptic vision and they are not comparable to point source resolution.

First, resolution as measured in photoptic light (daylight) may be twice but can be as much as 3x to 4x finer than that measured in scotoptic light (nighttime).

Second, resolution of linear features such as a black lines on a light background (high contrast line pairs) can be seen at R/3.5, where R is the value for point source resolution.

So a binocular that actually may be capable of seeing point sources no closer than 10 arcsec may give a line pairs resolution value of somewhere in the area of 3-4 arcsecond.

It's a good test, if used to compare to other binoculars that have been put through the same test. It is not a test that gives you directly a value for what you will be able to see in the night sky.

The results obtained in daylight with high contrast line pairs chart are not comparable to diffraction limits as determined by physics, the point source resolution or the Rayleigh Limit based on lens diameter.

see the discussion here on Binocular Resolution Testing w/USAF Charts

edz

[mooreorless]

The 36x24 Ednund poster of the 1951 USAF test sounds like what I had (missplaced long ago). If it is still the same it has different color, and as a result different contrast versions of the test pattern.

Henry,that is the same poster it has different color versions of test target.
Steve M

[DJB]

FYI all,

I have been using a Kodak IMAGE TEST CHART, P-301, CAT. No. 147 0475, circa 1970.

This is an acrylic/plastic type. It also passed MIL specs for our (special) projects.

It is not large, but it will perform well for optical testing.

Regards,

Dave.

[mooreorless]

Hi Dave,I would like to thank everybody for the information.Dave I couldn't find any information on the Kodak image test chart,p-301,cat.147 0475 .I did find a lens testing bench for $10,500 or 7,350 pound in case Kenny J is interested.I think I might get the Edmunds test target for about $18.Thanks.
Steve M

[DJB]

Hello mooreorless,

Yes, the Kodak test chart is an older one. Of course, the catalogue reference is older as well. I failed to verify its availability at the present time!

I would feel really comfortable with the ESC test target. I've delt with them for years now. Never a problem. Great luck in your choice.

Regards,

Dave.

[Pinewood]

Henry et al,

I do not consider myself very sensitive to color shifts, but I am capable of making comparisons. Today, I used the EII 8x30 on a stained glass window. There was a difference in color, or at least color saturation, between the port and starboard tubes. The yellow stained glass looked deeper in color, perhaps more orange in the right tube.
I should try this with one or two similar binoculars, perhaps a Nikon Se and/or the Leica BN.
In any case, I am surprised by this inconsistency. My guess is something happened in the application of the coatings as the only other culprit, different types of glass, is far less likely.
Any comments?

Clear skies,
Arthur

[Rich V.]

Arthur, did you by chance invert the binoculars and compare views to verify the difference in color balance stayed with the barrel orientation?

I ask this, since for me, my eyes seem to vary in their response to color at times. I sometimes notice one eye has a "cooler" color rendition than the other. This is not the case at this moment but it does happen from time to time. This phenomenon has caused me to think a binocular has a "cast" in one barrel only to find out it was ME!

Just a thought.

BTW, these threads of late about the demise of the E2 binoculars have made me go and order an 8x30 E2 to keep my old 7x35 E company! I've enjoyed the E for over twenty years; my only gripe is the 51° AFOV. (which somehow seems a bit wider than that) The wide field of the E2 will be a treat! It's sad to see the venerable German style Nikon porro design go by the wayside.

Rich V

[EdZ]

I see a completely different color between my two eyes in every instrument. I have one pupil that is a half mm larger than the other. That may not seem much, but it let's in 17% more light. That's a hugh amount, enough to alter the image of everything I look at. I don't even like to switch eyes at the telescope eyepiece because the image, on Jupiter for instance, in one eye will look yellow white, while the image in my normal viewing eye would be warm yellow.

edz

[Pinewood]

Rich and Ed,

There is now, no question that I perceive color slightly differently in each eye. This is a surprise!

Clear skies,
Arthur

[mooreorless]

The 36x24 Ednund poster of the 1951 USAF test sounds like what I had (missplaced long ago). If it is still the same it has different color, and as a result different contrast versions of the test pattern.

Hi Henry,I bought the test pattern off of Edmund's and here it is.I like to get back to people that have helped or just to make it more interesting and so other's can see what is out there.
Steve M

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[mooreorless]

another picture of it.

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[Henry Link]

Steve,

Yes, that's the one I used to have. Coincidentally I recently found a fragment of my old chart. I had cut out one of the black patterns long ago to make a smaller more easily usable target. Would you mind posting the formula for converting lp/mm to arc seconds as I don't have that part anymore. Thanks.

Henry

Henry

[EdZ]

Henry,

The forumla is dependant on also having the Table of Value Constants for each line pair image on the chart. Without the constants, the formula is of no use.

Also, it is extremely important that the chart be exactly sized. On occasion we see people that have photocopies of these charts. Almost all photocopy machines reduce the size of the original to maybe 97-98%. A copy of a copy can very quickly be reduced to a non-standard size and then the Table of Constants would no longer be valid for that copy. The other source is printing the charts off the internet as is possible from the links I've provided below. The caution here is the user must know exactly how to size the chart. As a check, the three bars and two spaces in Group-2 Element 1 should measure exactly 10mmx10mm.


I'll dig out the table of Constants and the Formula later and scan them with some sizing information and post it as pictures to our Binocular gallery.

See the discussion of USAF Charts here Binocular Resolution Testing w/USAF Charts

Here's an online link to USAF Charts
Lens Resolution Testing

I find it interesting that none of these links provide ALL the information necessary to use the charts. None of these links provide the formula.


and a link to a USAF 1951 Chart with the Table of Constants.
Chart with Table of Values
Using this table of values linked here which shows the constants for the Groups and Elements of the Line Pairs Chart, the forumula is

8121 / (D x LPM)

where D is the distance to your target measured in inches and LPM is the value from the Constants for the mimimum you can see. For instance a 10x binocular used at a distance of 125 feet that can see line pairs in Group-1, Element2 has a value of 0.561. Therefore it's resolution is 8121/(125x12x0.561) = 9.65 arcseconds.


edz

[Henry Link]

Ed,

Thank you very much. I had already copied the table from the Edmund website, but I couldn't find the formula there or anywhere else.

Henry

[mooreorless]

Steve,

Yes, that's the one I used to have. Coincidentally I recently found a fragment of my old chart. I had cut out one of the black patterns long ago to make a smaller more easily usable target. Would you mind posting the formula for converting lp/mm to arc seconds as I don't have that part anymore. Thanks.

Henry

Henry

Hi Henry,I see that EdZ already gave you the information you need.He is right on the stick. :bow:This test pattern is kind of big and I mounted it on piece 1/4 hardboard and then used drywall screws to mount it on an old wooden ladder I had.I just use a cordless drill to remove it from the ladder.I guess this should be mounted 6 ft. or more off the ground to get away from heat waves on the ground.The quality of this target is pretty good but I'm sure it doesn't compare to the other's of higher cost.The writing on it is very good,much better than the newspaper piece I mounted on it.The colored patterns look washed out in the pictures but are really pretty bright when looking at with binoculars.I like this test chart.I am happy to post these things on here.
Steve M

[mooreorless]

[quote name="EdZ"]Henry,

The forumla is dependant on also having the Table of Value Constants for each line pair image on the chart. Without the constants, the formula is of no use.

Also, it is extremely important that the chart be exactly sized. On occasion we see people that have photocopies of these charts. Almost all photocopy machines reduce the size of the original to maybe 97-98%. A copy of a copy can very quickly be reduced to a non-standard size and then the Table of Constants would no longer be valid for that copy. The other source is printing the charts off the internet as is possible from the links I've provided below. The caution here is the user must know exactly how to size the chart. As a check, the three bars and two spaces in Group-2 Element 1 should measure exactly 10mmx10mm.
[quote] edz
Hi Edz,
My brother gave me a Sept. issue of American Rifleman and in this issue there is an article by Bill McRae on testing binoculars and spotting scopes and it has a USAF 1951 Resolving Power Test Target printed with the article and I measured the Group -2 element 1 and it measured 10mmx10mm,it is pretty good copy but the Group 1 element 5 &6 are not real good but are ok.
Steve M

[mooreorless]

I believe it was Mark that asked for a Nikon 8x30 EII review on Cloudy Days.All this one needs are pictures.

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[Mark9473]

thanks Steve!

[mooreorless]

Hi Mark,I know you that you replied to this and others have seen this, but it is a very nice thread IMO.

[ngc6475]

It is indeed, Steve! You thoughtful reminder of this excellent discussion is both timely and welcome! Great snapshot, too!

[mooreorless]

Thanks Walter,some may ask what good is a birding review to us in an astronomy site,well birders are looking for wide in focus views just like us.Also I used your excellent Nikon 8x30 EII for very nice wide views of the sky,and now I use the little Leupold 6x30 Yosemite also for the same purpose.The 6x30 Yosemite showed me Jupiter and three of its moons this morning before I went to work,I will have to say that I could see the third moon easier with my Nikon 10x42 SE which is as expected.:-)