Canon ENG B4 Lens on GH1
- Thread starter bumkicho
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wbamb83392
Member
With a 2/3 3 chip lens on a 1/2" single chip sensor the CA is likely to be objectionable. I tried to use a 3 chip lens on a 1/2.5 format single chip sensor and found nasty red halos around everything. However, there are many existing 1/2" format single chip lenses from the CCTV world that would work for the GH2 in ETC mode. Few if any of the zooms were designed for high resolution, but there are C mount "megapixel" cctv lenses available that are quite fast and quite sharp wide open. I thought "megapixel" was a meaningless term like "digital ready", but the lenses from Fujinon that I tried actually were a lot sharper than the standard models.
Wont the resolution cut make it less objectionable?
wbamb83392
Member
I'm not sure what resolution cut you're referring to. On a GH1 it doesn't matter so much since 2x mode is just a half resolution crop. The ETC mode in the GH2 is a different matter, where the sensor is effectively 2.6 times smaller and the CA problem is 2.6 times bigger in every dimension. The easy test is to try it. If it turns out the CA really is objectionable, the proper optical adapter is only $5000 (!!).
Oh yes what was I thinking - Yes I meant the resolution drop from the crop - but yes I see now. However, using the in-camera crop allows you to not use the 2X extender on the lens, which with most lenses cuts down on CA a BUNCH. On a GH1, using the 2X on the lens gives acceptable CA (subjective of course to my eyes
with most high quality broadcast lenses that I have tried. On cheaper lenses, it gets worse. So I'm thinking with the 2X or 2.6 or whatever in-camera crop of the the GH2 will be similar to what I'm seeing with the GH1 and the 2X on the lens. I'm interested to find out how it is in real life though.Correct, unless you need the shallower DOF.
stonebat
Veteran
That's not a bad thing.
The benefit of ETC is less sacrifice in sharpness which gives deeper DOF. Since ENG lens doesn't have great bokeh in low lighting, I prefer deeper DOF. Should be easier to focus, too.
I'm waiting for Canon YJ18x9B4 KRS SX12 Internal Focus f/1.8 lens delivery. I paid $500 + shipping. No 2x extender as the recent prices have spiked up... easily over $1K. If the prices of used ENG lenses stay so high, I don't think this will become popular option for GH owners.
The benefit of ETC is less sacrifice in sharpness which gives deeper DOF. Since ENG lens doesn't have great bokeh in low lighting, I prefer deeper DOF. Should be easier to focus, too.
I'm waiting for Canon YJ18x9B4 KRS SX12 Internal Focus f/1.8 lens delivery. I paid $500 + shipping. No 2x extender as the recent prices have spiked up... easily over $1K. If the prices of used ENG lenses stay so high, I don't think this will become popular option for GH owners.
That's not a bad thing.
The benefit of ETC is less sacrifice in sharpness which gives deeper DOF. Since ENG lens doesn't have great bokeh in low lighting, I prefer deeper DOF. Should be easier to focus, too.
I'm waiting for Canon YJ18x9B4 KRS SX12 Internal Focus f/1.8 lens delivery. I paid $500 + shipping. No 2x extender as the recent prices have spiked up... easily over $1K. If the prices of used ENG lenses stay so high, I don't think this will become popular option for GH owners.
The prices have only gone up for IF lenses - the non-IF lenses continue to be dirt cheap. You can get a high-end non-IF broadcast lens with a 2X extender for under $500 easily. However, IF lenses will continue to be high since they are still in demand for ENG cameras. You didn't get a bad deal on the 18x9 - that is what I usually sell them for.
wbamb83392
Member
According to my math, the ETC mode has a depth of field .34 times greater than full frame mode with a doubler given the same field of view. A depth of field of .5ft becomes .67 for instance. What you gain is 2 f stops of light and what you lose is a wider field of view at the wide end of the lens.
wbamb83392
Member
Is the ETC image circle really 9mm? A standard 4/3 image circle divided by 2.6 is only 8.31mm. My 1/2" format zoom lenses have minimum image circles around 8.6mm and they're very consistent across 5 different brands. The only 1/2" fixed focal length lens I have is a panasonic 6mm f0.75, and it has a 10mm image circle. I don't have a GH2 on which to test them, unfortunately.
In 16:9 mode, sensor active area is 18.8mm X 10.6mm, in 4:3 mode is 17.3mm x 13mm. 18.8 divided by 17.3 is 1.0867 or 9% (rounded) difference. This is the reason why the same lens in 16:9 mode offers a slightly wider FOV. The crop factor is near 1.85 instead of 2X.
1.85 x 2.6 = 4.81. If you divide 43.26mm (35mm sensor/film area) by 4.81 you get a 9mm circle. Again, 43.26 / 3.93 (2/3" crop factor) gives 11mm; and 43.26 / 5.4 (1/2" crop factor) gives 8mm.
Hence my doubt about 1/2" lenses performance on GH2.
However, I don't have a GH2 too, so I can only speculate...
wbamb83392
Member
Panasonic says the sensor in 4:3 mode is 17.3mm wide and the highest quality 4:3 photo is 4608 pixels across. Assuming the camera doesn't do anything weird with pixels, that sets the pixel size at .00375mm. Multiply by 1920 and the ETC mode width is 7.2mm giving a 16:9 image circle of 8.26mm. To have a 9mm image circle in ETC mode the sensor width in 4:3 mode would have to be 18.8mm, which is 1.5mm wider than Panasonic claims.
Indeed, in 16:9 mode the actve area is 18.8 x 10.6 millimeters compared to 17.3 x 13 millimeters in 4:3 mode.
http://forums.dpreview.com/forums/read.asp?forum=1041&message=36396593
wbamb83392
Member
To have a 9mm image circle in ETC mode the sensor width in <<4:3 mode>> would have to be 18.8mm, which is 1.5mm wider than Panasonic claims. In other words, the sensor in 4:3 mode would have to be 18.8 x 14.4 millimeters not 17.3 x 13.
wbamb83392
Member
Today I mounted a 1/2" 3 chip lens (Fujinon gemini S12x6.6 with a doubler) to a GH1 and took some quick stills to see just what the chromatic aberration looks like. The top 4 photos are at different f stops, and as you can see the lens is really soft wide open. This is because the the red, green, and blue parts of the spectrum focus on different planes.
The bottom photos show the focal length range. In practical use it would be a 6.6-160mm f4 lens with a servo zoom.
The bottom photos show the focal length range. In practical use it would be a 6.6-160mm f4 lens with a servo zoom.
Yes, also to be honest the Fujinon Gemini is not a broadcast lens, and would be a little soft even on a 1/2" video camera.