New achromat Letus EX on Ex-1 and HVX

L

Lenilenapi

Carbonite Member
I shot a few more tests with the improved Letus Extreme achromat on both my HVX and my Sony Ex-1 this evening and the basic results are that it seemed to work well on both.

On the HVX it seems to hit center and corner at the same point so the soft corner issues may be over. On the Ex the corner and center are a little different so a mid focus works better.

I think on both you can use both Academy and SLR but at first glance Academy might be a bit softer on the HVX. I don't have time to stare at these too much right now though and I won't get to post them till Sunday at the earliest.

Oddly on my test it seemed to lose more light than the old achromat on the HVX - but there is possibility of error there as I didn't recheck my naked HVX at the same time. Its really easy to make a mistake on these tests. What i saw was it needed 32 footcandles instead of 24 with the old achromat. Naked HVX was only 12footcandles. Sorry I can't be more sure since it does seem very odd. Could just be a different meter.

It is sharp though - promise.

Lenny Levy
 
Lenilenapi said:
I shot a few more tests with the improved Letus Extreme achromat on both my HVX and my Sony Ex-1 this evening and the basic results are that it seemed to work well on both.

On the HVX it seems to hit center and corner at the same point so the soft corner issues may be over. On the Ex the corner and center are a little different so a mid focus works better.

I think on both you can use both Academy and SLR but at first glance Academy might be a bit softer on the HVX. I don't have time to stare at these too much right now though and I won't get to post them till Sunday at the earliest.

Oddly on my test it seemed to lose more light than the old achromat on the HVX - but there is possibility of error there as I didn't recheck my naked HVX at the same time. Its really easy to make a mistake on these tests. What i saw was it needed 32 footcandles instead of 24 with the old achromat. Naked HVX was only 12footcandles. Sorry I can't be more sure since it does seem very odd. Could just be a different meter.

It is sharp though - promise.

Lenny Levy
Click to expand...

This is very unexpectedly great news! The HVX actually perfoms *better* than the EX-1 with the EX-1's custom achromat? Wow...

As you may recall from my initial impressions of my HVX/LEX/Zeiss 50mm test, it was far from satisfactory e2e.

I will await your screenshots with great anticipation. Please, along with the rest, show us worst-case if you could - both HVX and taking lens at wide open. If that only shows softness that can be attributed to the lenses (which would mean it couldn't be improved by edge-refocusing the HVX) then I will be *thoroughly* impressed.

Thanks again Lenny
 
Last edited:
I have been thinking about my results overnight and want to just make a few caveats here,.

1. On the Sony EX-1 my lower left corner is not sharp. Hopefully Hien will correct that, but it does imply that tolerances might be tight. Just an implication since its also possible that my unit is way out of alignment. But if mine is how many others might be? I urge others to also test with a chart.

2. On the HVX I noted that I need more light with the new achromat. Since it seems odd I thought that might also be a mistake. But perhaps its not. I checked my 2 meters last night and they are in sync. However what I saw was a total loss of 1 1/2 stops or so. That's not good.


Again I urge someone else to do the same test. I have other things to do in my life than just repeat these tests.

Ted - all my tests unless otherwise noted are worst case wide open on both lenses.

Lenny Levy
 
Last edited:
My EX-1 Achromat Replacement should be here any day now, I'll check the whole 1 1/2stops of light by switching Achromats on the fly. I don't have my light meter or anything like that just yet but a tripod test in a room with lights on should easily tell if you're losing a completely ONE stop of light with the new glass.

Thanks for pre-testing.

Edit: Did the Achromat just go right in or what? Or does it still need it's own ring for the HVX?
 
Seems quite odd that swapping out an achromat should cost that much light. I'm sort of surprised to hear that it costs *any* light, but I'm certainly not the expert where optics are concerned.
 
Yeah, I'm with you Ted. It'd be interesting if it actually costs 1 stop of light just between swapping achromats.

That's also why I ask how it's being secured, I thought that it needed it's own ring but I could be wrong again.
 
I have an early version of Letus Ex apparently that the achromat doesn't screw out on, so replacing the achromat was a bit of a pain. It is in a rubber sleeve that you have to pull out and then insert again with the new achromat. takes a bit of time and is a bit sloppy.

I agree that the loss of light - more like 1/2 - 2/3 stop by the way seems odd to me to that's why I'm a bit skeptical of my own numbers, but I didn't want to take the time to retest it again as I needed to send it back to Hien ASAP for re-centering the optics.


Lenny
 
I have the same one, rubber back, as mines was one of the earliest versions.

No worries, as soon as I get the EX-1 Achromat I'll report on the light loss but I seriously can't fathom why it would change light loss if it's just replacing the glass and not adding?

I don't have a light meter yet, is there any other way you would suggest testing it outside of say recording the image with the old achromat and then inserting the other and recording again?
 
Yeah i think that would work. Record an image - best if its something you know won't change while your changing the achromat. Easiest if the video camera is wide open so you the vague f stops settings won't be changeable. Probably best to have the center of the image on something like a piece of paper so you could get an IRE reading in the viewfinder from it, and write the reading down.
Then make sure you match the frame size when you put on the new achromat. Let me know. Glad to have a second eye looking at it.

I hope I made a mistake.

Lenny
 
Hien Le just emailed me that there was no additional light loss with the new achromat, so i'm going to assume that this was my error until I get a chance to double check it.

- Lenny
 
Hien contacted me today to let me know that my Letus apparently has a broken prism and perhaps that's been so since I got it.
So i guess I will now have to redo all my tests when I get a new one in a few days.

Lenny
 
the HVX corrective achromat should be along shortly (according to Letus)

I can wait to see it in action, Im happy with the current setup, so any improvements will be GRAVY!!! Im buying one right off if it does what it is supposed to.

Thanks for all of the testing Lenny
 
You must log in or register to reply here.
Back
Top