Stills of Focus charts from Panasonic HVX200 and Sony EX-1
with Brevis, SGPro (Rev2) , and Letus Extreme (2/16/08)
(Ex-1 tests without the corrected achromats)
These tests were designed to put to the test many claims that have been made by people on the Web regarding how sharp (or more often how not sharp) various 35mm adapters are, how much light they need, etc. All I did is photograph with a standard ISO resolution chart you can download below.
I used what I had - including an outdated SGPro Rev2 - however the Rev 3 should not differ optically from the current version.
I measured footcandles with a lightmeter that was not digital so the numbers are estimates between meter markings.
I was not precise about lighting but just bounced a light into the ceiling so I did not attempt to make a perfectly even field. It should generally be hotter near the top and probably falls off around the sides. I aimed for a waveform reading of 90 IRE on the center of the chart and generally adjusted the light to make that close. But sometimes to get higher light levels I moved the bounce closer probably making the bottom and sides even darker.
Don't judge eveness of exposure ( except on the Sony EX shots where vignetting is a problem) from these tests. The light meter readings were done on different days and I expect there are some inconsistancies so don't get hot and bothered about minor difference. Look for significant differences.
I mislabeled some of these shots and also had the colorbalance off, so I have repaired the labels in Photoshop (very crudely) and desaturated some of the off balances. I probably made other mistakes as well.
I may not have always hit the sweet spot for mid focus as I was doing this alone, so it could be off a bit on some shots. Also the brightness of these stills generally seems much lower than they looked on my 17" Panasonic monitor . Sony EX-1 tests were not done with the new achromats designed to correct those problems.
. Sony EX-1 tests were not done with the new achromats designed to correct those problems.
These tests did not look at Bokeh or quality image, and I do not endorse any specific adapter - indeed it seems they all came off well.
My conclusions from quick looking:
You can easily see the controversial Brevis CF1L iris affect - There is no change in exposure when you change the Nikon from to 1.4 to 2.8 and little as you go to f4. I also saw no no change in DOF from 1.4 to 2.8 either.
The DOF comparisons show the big difference between the Brevis and an SGPro. To measure that simply focused a 50mm lens at infinity and shot it at 6' away to show the difference in out of focus quality. It is striking.
You can see the loss of sharpness from a naked camera easily, however on the HVX all 3 adapters have good enough sharpness and center to corner focus IF YOU FOCUS ON A MID POINT between center and corners. You can also see that a 50mm nikkor at f1.4 looks pretty decent corner to corner.
The Brevis flip with the Brevis is the only flip unit that consistently hit the corner and the center focus at the same point exactly. However if you take the time to focus on a mid point with the SG and the Letus they are all acceptably sharp. This probably means not relying on autofocus or just quickly focusing on the center of the screen. You usually need to go a bit past the center focus point. You can decide of one looks better than another, but I wouldn't take minor differences to seriously as it could be my errors. I haven't really looked to see if one is overall sharper.
There was some CA on all of them, but I never saw this on my 17" Panasonic monitor, only on these stills. It is actually surprising how much I see on these stills. The Flip on The Brevis seemed to clean up its CA a great deal.
I saw no advantage to zooming in on the Letus for getting a flatter field - to the contrary it was worse.
On the Sony EX-1 I saw very similar issues of soft corners on all three adapters + at least some vignetting issues on all 3. With all 3 it seemed that the corner issues were resolved by f8 on the Ex-1 so for exteriors you could get excellent pictures.At f 5.6 the corners were perhaps acceptable on some shots - it depends on the shot and your standards. With more open iris you are on your own.
On my EX-1 I got the least vignetting with the Brevis Flip and Brevis combo. Because of its speed it seemed I could shoot interiors with aproximately 100+ footcandles at 1/32 shutter and a 2.8 Nikkor and get away with fair corners at f5.6. Maybe you will still need a little more light though I only tried to get a chart to 90.
The new achromats from Letus and eventually from Brevis should eliminate these problems, but if you need to shoot with the old ones I hope this is helpful.
I think its also clear from these tests that you can get reasonably sharp center to corner images from a Nikon 50mm @ f1.4.
My settings on the HVX were HD Norm, 1080P 30P, 1/30 shutter, knee on high, Detail @ +2
On the Sony Ex I started with 1080, 24P, 1/32 sh and Cine 3 gamma , but changed to Std2 gamma with auto knee for the last EX tests @ 5.6 and 8
Lenny Levy <http//:www.leonardlevy.net>
ISO RESOLUTION CHART (You can take this file to Kinko's and blow it up to 4' or so, and tape it to a card. Do your own tests and carry a card to your gigs to check focus)
HVX200 tests all w/open iris and full SLR framing unless noted
HVX200 with Original Brevis (w/CF1L) and SGPro (Rev2) :
HVX200 with Brevis Flip on the Brevis (CF1L) and SGPro (Rev2) :
HVX200 with Letus Extreme:
Sony EX-1 with Letus, Brevis Flip + Brevis, and BrevisFlip + SGPro:
-These tests are with the original Letus and Brevis achromats - not corrected for the Sony EX-1
-All Letus images are zoomed in past Academy to avoid vignetting
-These tests were only for focus issues so other information - Foot candles etc is omitted-Focus is usually at the Mid (BEST) position so as to show when the adapters are best case
DOF TESTS: On these shots a 50mm Nikkor was set to focus on infinity but shot from 6' away to show the relative DOF of the adapters. I only used an HVX and only compared the Brevis and the SGPro, both through a Brevis Flip.