sgpro vs letus vs brevis:resolving power test

shiny4

shiny4

Well-known member
about the bokeh ,the edge to edge sharpness,the light lost we have discussed a lot.
but what about the real resolving power of each adapter ?
700 line-800 or less or more??
my first question is:
what give a better resolution??
ground glass or achromat or both??
second question:is it possible to know the real resolving lines of the three adapters?
this is what i would like to find in each manual shipped with the adapter.
any news and scientific test??
p.s.:give a look here to see the difference between sharpness and resolution:
http://www.cambridgeincolour.com/tutorials/sharpness.htm
 
Last edited:
Well, here's a grab we just did testing the little Canon HV30 (single CMOS, 1920x1080) using our CF1 imaging element. This is using a Nikon f2.8D zoom lens at 35mm, f2.8. The HV30 is at 1/48s, and f3.2. The DSC labs back focus chart goes to 1600 TV LPPH, and you're seeing the camera just breaking the 800 line mark. Note that I lit this overhead with one light for the frame grab...so it's a bit hot at the center. We'll be baselining the HV30 properly with our Ambi2 (rear illuminated chart) system next week. The HV20 has more resolution at f5.6 over what we shot this at, f3.2...so I think we'll do bit better yet.

hv30.jpg
 
shiny4 said:
about the bokeh ,the edge to edge sharpness,the light lost we have discussed a lot.
but what about the real resolving power of each adapter ?
700 line-800 or less or more??
my first question is:
what give a better resolution??
ground glass or achromat or both??
second question:is it possible to know the real resolving lines of the three adapters?
this is what i would like to find in each manual shipped with the adapter.
any news and scientific test??
p.s.:give a look here to see the difference between sharpness and resolution:
http://www.cambridgeincolour.com/tutorials/sharpness.htm
Click to expand...

There are way too many factors involved to even consider believing one manufacturer over another. I'd leave something like that up to Leni to be honest, because he'll be able to use the exact same camera, exact same lens on each.

The idea test bed would be the Optimized Test Bed: Sony EX-1, PL Mount for each adapter or a Zeiss lens, controlled lighting, exact same frame zooms and exact same frames in general.

The EX-1 because it's a full 1920 x 1080 frame.

IN the end, it's really just too difficult and time consuming although Leni does a good job at these kinds of things.
 
We do this testing, having invested a great deal in equipment to do it, to make sure our customers have accurate expectations with our equipment. Price out a set of DSC labs charts and perhaps their Ambi2 rear illuminated system and you'll get an idea of just how serious we are about this. As with our light loss linearity observations, expanding understanding of how to get the best images from our equipment is something we've been quite dedicated to. The Cinevate forum has many posts, good, bad and ugly with results from our various users...and my personal committment is to make sure their results look as good as ours.

Every test I do lists equipment used, lenses used, f-stops set etc. etc. Given the web stats on our video university section of the site, I'd say adapter users are looking for hard data on adapter performance...and at least from us, they're getting it.

It's guys like Lenny who push the envelope of testing in his own selfless manner that have encouraged us to invest in professional tools to quantify the Brevis optical performance. Unless I'm missing something, Lenny's "home" tests have pretty much 100% corroborated what we've reported.

The test setup from which that grab was taken:

hv30testing.jpg
 
Thanks for the kind words guys.

Kholi's right in that its very hard to come up with accurate measurements comparing adapters . Lots and lots of variables and nobody is paying me or anyone else to do it.

Each manufacturer can and should be doing it for themselves and Dennis's commitment to his own standards is admirable. But of course you can't expect Dennis to compare his adapters with the competition and then publish the results.

My own tests were pretty accurate and careful I think but very limited in what they were looking at - speed, DOF and corner to center focusing. You can see looking at them that some other variables are completely sloppy so i just warned people to ignore them.

I haven't looked at a Redrock in a long time, but one thing I do feel I can say is that Letus, SG and Brevis are all reasonably sharp at this point. Is one significantly sharper than the others - I don't honestly know.

Lenny Levy
 
And more than likely it'll come down to preferences, trade-offs, etc etc anyway. The real issue is the camera to be honest. The HVX200's resolution is lower than the EX-1 and even the A1 looks like it resolves more than the 200 with or without the adapter.

At a certain point the camera factor needs to be re-introduced and weighed in on. I keep saying it, but that's why I'm excited about Convergent designs' XDR and nanoFlash. With the 170 it'll be great.
 
Not sure how much sharper the 170 with the CDesign will be. Better color space and compression, yes. Resolution will still be 960x540, shifted and upscaled to our general disappointment.
 
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