GH2 25mm lens + ETC mode = 50mm lens?

Jaime Valles

Jaime Valles

Veteran
Hello, all. I'm wondering about the use of the ETC mode on the GH2. If I have a 25mm lens on the camera, and I turn on the ETC mode, do I get the same image as if I had swapped out the lens for a 50mm one? I'm curious about field of view, bokeh, brightness, etc.

I'm asking because I have the much sought-after Voigtlander 25mm f0.95 lens here, and was considering buying a 50mm lens, but not if the 25mm + ETC give me the same thing for free.

Thoughts?
 
You won't get the same image, as the focal length doesnt change, meaning you're DOF won't change, it will just be cropped. the field of view will be different, as it's basically like using a smaller sensor, same way that m4/3 is 1/4 the size of a 35mm still's camera which is the "standard", so you can kind of see it as m4/3 as the "standard" and the ETC as the crop.
Bokeh shouldnt change, as that's defined by the lens, so you get the same bokeh, just less due to it being cropped, and again, brightness won't change as there's no optic's absorbing light in the same way as a teleconverter, you might not be able to up the ISO as high aswell as ETC seems to exaggerate it somewhat
 
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due to the 2x crop factor you get 50mm out of the box. with ETC you get additional 2.6x factor in 1080p (130mm) or 3.9x in 720p, which is 195mm.
 
Any cropping including ETC gives less circle of confusion for bokeh. i.e. less pleasing bokeh. I think ETC is most useful to those wildlife birdmen. ETC amplifies noise size. Not so useful in high ISO. I'd get inexpensive vintage 50mm 1.4 lens.
 
Thanks all for the replies.

himynameisnathan said:
You won't get the same image, as the focal length doesnt change, meaning you're DOF won't change, it will just be cropped. the field of view will be different, as it's basically like using a smaller sensor, same way that m4/3 is 1/4 the size of a 35mm still's camera which is the "standard", so you can kind of see it as m4/3 as the "standard" and the ETC as the crop.
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That makes sense.

Bokeh shouldnt change, as that's defined by the lens, so you get the same bokeh, just less due to it being cropped
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I would think the bokeh would appear larger, since I'm essentially blowing up the cropped image, no? Same amount of bokeh, but more magnified?

brightness won't change as there's no optic's absorbing light in the same way as a teleconverter, you might not be able to up the ISO as high aswell as ETC seems to exaggerate it somewhat
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That makes perfect sense.

brudney said:
due to the 2x crop factor you get 50mm out of the box. with ETC you get additional 2.6x factor in 1080p (130mm) or 3.9x in 720p, which is 195mm.
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I understand your point, but I'm not referring to Full Frame 35mm photography, I'm only interested in 1080 HD video. A 25mm lens looks about the same on the GH2 as on a motion picture 35mm camera. Full Frame 35mm (like in the 5D Mark II) is irrelevant to me.

stonebat said:
Any cropping including ETC gives less circle of confusion for bokeh. i.e. less pleasing bokeh. I think ETC is most useful to those wildlife birdmen. ETC amplifies noise size. Not so useful in high ISO. I'd get inexpensive vintage 50mm 1.4 lens.
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Yeah, I'm thinking one of the Canon FD 50mm lenses on eBay. Any good recommendations for MFT to FD adapters?
 
Even better... Would somebody that owns a 25mm lens and a 50mm lens post some 1080/24p screen grabs of the following:

25mm standard
25mm in ETC mode
50mm standard

That way, I could really see the difference in the quality between the three. If somebody could do that, I'd be very grateful.
 
In ETC mode, you get a 25mm f0.95 lens designed for m4/3 format on a ~1/2" format so the image is cropped about 2.6x. In terms of m4/3, your fov and dof will look somewhat like if you put a 65mm f2.5 on your gh2 without ETC but it will likely be a little soft as the lens is not designed for such small coverage.
 
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nyvz said:
In ETC mode, you get a 25mm f0.95 lens designed for m4/3 format on a ~1/2" format so the image is cropped about 2.6x. In terms of m4/3, your fov and dof will look somewhat like a 65mm f2.5 but it will likely be a little soft as the lens is not designed for such small coverage.
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Excellent point about sharpness. The question then becomes: Is a new Voigtlander 25mm lens sharper in ETC mode than a vintage 50mm Canon FD lens in standard mode?
 
Jaime Valles said:
Excellent point about sharpness. The question then becomes: Is a new Voigtlander 25mm lens sharper in ETC mode than a vintage 50mm Canon FD lens in standard mode?
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Do keep in mind that they are quite different imaging systems. Your DOF will be almost 3stops shallower on a 65mm without ETC than a 25mm with ETC 1080p despite having the same FOV. Also ETC mode is known for having higher noise and less resolution than standard 1080p mode.
 
nyvz said:
Do keep in mind that they are quite different imaging systems. Your DOF will be almost 3stops shallower on a 65mm without ETC than a 25mm with ETC 1080p despite having the same FOV. Also ETC mode is known for having higher noise and less resolution than standard 1080p mode.
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How can it have less resolution if it is using a 1080p crop natively with no downscaling?
 
flinty said:
E-T-C in 50i or 24P is lossless as far as i can tell but in 720P the quality is poor ie noisy and soft.
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Actually in 720p mode it has the exact same sharpness as in 1080p mode. Both modes use 1:1 pixel mapping. Think of it as just a cropping mode. However, it will exaggerate noise. And in the 720p mode you will exaggerate that noise even more if your monitor has a greater resolution than 720p.
 
flinty said:
It is a shame the GH2s 720P E-T-C is not lossless like the other frame rates,i would prefer 2.6 lossless to degraded 3.9, here is a test i did with 720P E-T-C if the clip is not marked it is as the last marked clip,there only a few clips with E-T-C off http://www.youtube.com/watch?v=c7tecfq_830
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That is wrong. The 720p is lossless just like the 1080p mode. They are both 1:1 pixel mapped modes. If you display the 720p ETC mode on a 720p monitor it will have the exact same perceivable resolution as the 1080p mode displayed on a 1080p monitor.
 
mpgxsvcd said:
That is wrong. The 720p is lossless just like the 1080p mode. They are both 1:1 pixel mapped modes. If you display the 720p ETC mode on a 720p monitor it will have the exact same perceivable resolution as the 1080p mode displayed on a 1080p monitor.
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well i think different,playing a 720P clip filmed with E-T-C on dirrect to any of my tvs they are 1920x1080P and 1920x1080i and the grainy soft difference is obvious to E-T-C off,i also have a 720P tv in my pc room that shows the big degradation,so i beg to differ.
 
flinty said:
well i think different,playing a 720P clip filmed with E-T-C on dirrect to any of my tvs they are 1920x1080P and 1920x1080i and the grainy soft difference is obvious to E-T-C off,i also have a 720P tv in my pc room that shows the big degradation,so i beg to differ.
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I bet the camera is actually outputting 1080i to the TV's. You have to examine the files on a computer so you make sure there isn't any manipulations going on.



I will post some samples that demonstrate this.
 
himynameisnathan said:
How can it have less resolution if it is using a 1080p crop natively with no downscaling?
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I haven't tested 1:1 not-downrezzed modes (those being ETC and still photos) much, but it's possible they outresolve $100 kit lenses. High pixel density is a major downside of 4/3" format (.wish they could've just made the entire sensor 1920x1080 and forgotten about it being a half-assed still camera)

With a legit lens, you're right, I don't see how that's possible.
 
Jaime Valles said:
Even better... Would somebody that owns a 25mm lens and a 50mm lens post some 1080/24p screen grabs of the following:

25mm standard
25mm in ETC mode
50mm standard

That way, I could really see the difference in the quality between the three. If somebody could do that, I'd be very grateful.
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25mm Zeiss ZF @ f/2.8 (wide open):
http://dvxuser.com/barry/GH2/25mm.jpg

25mm Zeiss ZF @ f/2.8 with ETC:
http://dvxuser.com/barry/GH2/25mm-ETC.jpg

50mm Zeiss ZF @ f/2.8:
http://dvxuser.com/barry/GH2/50mm.jpg
 
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