GH4 GH4 Penalty for using EX Tele mode?

E

Ed Jeffersen

Active member
What are the downsides to shooting video with the Ex Tele option? In particular what happens to the depth of field? Say we are using a 20mm lens at f2/0 with the subject at 6 feet.

Using only a small portion of the sensor it seems would essentially reduce the size of the chip to roughly equal that of a point and shoot or camcorder?

I know of one benefit besides the obvious 2X crop. That is the reduction of the dreaded moiré.

How about the general quality of the image?
 
The Ex Tele option takes a 1:1 sampling of the sensor to achieve the "crop". It loses no quality whatsoever from normal 1080p. You cannot use it in 4K mode though. I use this feature often to give some of my lenses extra reach but just know that it does not affect DOF, just FOV.
 
DOF should be the same. Just because one crops the sensor doesn't mean the physical characteristic of the lens and camera change. Think of it like shooting an image at a certain DOF and then cropping it in Photoshop to 1/2 the size. The image is smaller but the overall look and DOF is still the same.

While yes true ETC doesn't lose quality it isn't exactly as good as native 1080p from the GH4 or 4k down converted to 1080p. Part of what makes DSLR video very good is the over sampling nature of a larger than 4k sensor. Even the GH1, GH2 and GH3 benefit from this over sampling concept. Things like noise and fine detail are higher when you start with an over sampled source. By shooting ETC you effectively remove the over sampling from the camera and just grab the 1920x1080 center portion of the sensor. In terms of 1:1 pixel values this is great but you do not get any of the benefits of the normal over sampling mode.

ETC is known to show noise a lot easier at higher ISO levels. This is because the pixel binning process helps clean up or hide the noise. While ISO1600 can be considered pretty decent shooting normal HD, ETC can only really go up to ISO400 before starting to see the same amount of noise.

The GH4 is also a single sensor camera which means not every pixel has accurate color. With normal shooting and when users shoot 4k and down convert the loss of color data is compensated for. By shooting ETC you are only getting the de-bayered 1920x1080 center pixels from the sensor. Not only is the color detail going to be less accurate but the overall image will likely be a bit softer. Bayer sensors can never resolve the full pixel detail one would expect. It is impossible to gain true 1920x1080 pixels of resolution. This is why some single sensor cameras that only have a 1920x1080 sensor look so soft compared to even the GH1.

So you don't lose resolution but at the same time you will not resolve as much raw detail.

Now ETC can actually gain a few things like less moire and aliasing. Pixel binning is a crude way of down sampling a larger than 4k sensor and the side effects are aliasing and moire. By shooting ETC you no longer deal with pixel binning and you can actually get less moire in the video. 4k shooters enjoy this benefit as well since they are basically using the same concept as ETC and shooting with the 4k center of the full sensor.
 
I agree with Thomas Smet's comment "So you don't lose resolution but at the same time you will not resolve as much raw detail." I have never been happy with any ETC shot footage with my GH4. This is causing me to save up for the Pany 100-300mm lens or maybe a 300mm prime.
 
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The ETC mode of the G6 and GH4 is the one feature that sets it apart from any other cameras on the market. In the simplest terms it is astounding.

Here's one I just did last month with a 100-300 in cineV all zero's 16-235 at a equivalent focal length of 1500mm.
https://vimeo.com/116448341

The tiny difference in detail with ETC vs. the same equivalent focal length in 4k down sampled to 1080 is insignificant compared to the content you can fill the screen with. Content is king! Get that image in your face and all this other little pixel peeper whining goes away right quick. Take a 50mm f/1.4 lens in ETC and you get a 250mm equivalent at f/1.4 There is no such thing ever made for any camera that can compare.

Here's an older one I've shown a number of times with a G6 and a 600mm lens in ETC for an equivalent focal length of 3000mm.
https://vimeo.com/90916591

The Panasonic ETC function is the single most amazing tool put in a camera since HD came along IMHO !!!

Cheers,
Pete
 
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Thank you all, I learned a lot..
Basically the relationship between lens and sensor does not change so depth of field remains constant. That is good news. I had not considered the noise increasing. That is a big one, but with fast glass I can stay at ISO 200-400.
Moiré is ruining a lot of my shots. Certain fabrics are psychedelic! I prefer to shoot AVCHD 1080p for archival purposes. I don't edit or format my cards until I have 2 copies of the original footage. (do we still call it that?)
I have 3 choices:
1) Shoot 4K, and archive after downsizing to 1080. A longer work flow.
2) Use ETC. Positives and negatives there.
3) Use my AF100.
Option 3 is becoming the most appealing for a certain job I do most often - talking head interviews. The audio is there too. I just love that GH4 image though.
 
c3hammer said:
The ETC mode of the G6 and GH4 is the one feature that sets it apart from any other cameras on the market. In the simplest terms it is astounding.

Here's one I just did last month with a 100-300 in cineV all zero's 16-235 at a equivalent focal length of 1500mm.
https://vimeo.com/116448341

The tiny difference in detail with ETC vs. the same equivalent focal length in 4k down sampled to 1080 is insignificant compared to the content you can fill the screen with. Content is king! Get that image in your face and all this other little pixel peeper whining goes away right quick. Take a 50mm f/1.4 lens in ETC and you get a 250mm equivalent at f/1.4 There is no such thing ever made for any camera that can compare.

Here's an older one I've shown a number of times with a G6 and a 600mm lens in ETC for an equivalent focal length of 3000mm.
https://vimeo.com/90916591

The Panasonic ETC function is the single most amazing tool put in a camera since HD came along IMHO !!!

Cheers,
Pete
Click to expand...

I agree with you to a certain degree as long as you are outdoors in good lighting. The detail is not as much of a concern as is the noise when shooting with ETC mode. If you have fast glass or good lighting not as much of a concern but for those that think the GH4 already isn't great in low light it gets much worse when using ETC.

Another thing to factor in is the optical quality of the lens. Some vintage lenses that have a softer look fall apart even faster when using ETC mode. The over sampling of the image helps with lower quality glass as well. Softer lenses will look more detailed. By shooting ETC you may get even softer video with those older lenses. Native m43 lenses tend to work very well in ETC mode due to their insanely sharp nature. Well made adapted modern lenses work much better as well. The rule is the lower the optical quality of the glass the worse it will look with ETC. Lenses that take super sharp stills will handle ETC much better. Normal shooting can be a bit more forgiving of lens quality which is why we typically hear people say a certain lens is ok for stills but looks great when used for video.

I agree content is king which is why ETC is a great feature to have. I use it myself when I have need. It still pays to know what is going on with the image however and what the trade offs are.
 
@Mark Williams... I think you'll be pleasantly surprised by the Panny 100-300 lens. I've been using it a lot recently filming surfing. It needs a bit of rigging to support the lens though, and I cant believe how well its OIS works whilst panning on sticks, throwing the focus about (stopping at an end point when panning with OIS on sticks can catch you out) Have used the ETC (a few times with OIS on) and it ain't too shabby if you pick the right shot.
 
What was your frame rate when shooting those bucks? I can't remember if the frame rates are limited in ETC mode. That footage was nice.
 
Ed Jeffersen said:
Thank you all, I learned a lot..
Basically the relationship between lens and sensor does not change so depth of field remains constant. That is good news. I had not considered the noise increasing. That is a big one, but with fast glass I can stay at ISO 200-400.
Moiré is ruining a lot of my shots. Certain fabrics are psychedelic! I prefer to shoot AVCHD 1080p for archival purposes. I don't edit or format my cards until I have 2 copies of the original footage. (do we still call it that?)
I have 3 choices:
1) Shoot 4K, and archive after downsizing to 1080. A longer work flow.
2) Use ETC. Positives and negatives there.
3) Use my AF100.
Option 3 is becoming the most appealing for a certain job I do most often - talking head interviews. The audio is there too. I just love that GH4 image though.
Click to expand...

Option 3 is probably the best for workflow. Option 1 for ultimate quality. I guess it depends on what you want. There have been jobs where I just wanted to do as efficiently as possible, so I know how you feel.
 
maranfilms said:
What was your frame rate when shooting those bucks? I can't remember if the frame rates are limited in ETC mode. That footage was nice.
Click to expand...
Thanks! There's no upper limit for shutter in ETC only a lower limit of 1/frame rate. I shoot 1080-60p at 1/60th second for all my wildlife work. Occasionally when it is really dark at dawn and dusk I will shoot 1080-30p at 1/30th second. I think more motion blur is always more appealing to view than stutter I see with a 180 shutter angle.

Cheers,
Pete
 
edmundronald said:
Why do ETC rather than just crop 4K to HD in post after stabilising in post?

Edmund
Click to expand...

Because one may want to shoot 60p. You cannot shoot 60p at 4k on the GH4. Also the ability to shoot 200mbps all-I while using ETC could be very attractive when shooting high levels of motion or detail. 4k at 100mbps is a tad low (think HD at 25mbps roughly) and the artifacts will show up even more by cropping in post. Shooting ETC at 200mbps would be vastly superior in terms of compression.

One other thing to consider is using an external HD recorder for even better quality when shooting ETC. You could end up with a little bit better color (4:2:2, 10bit) and much less compression compared to cropping 4k in post. Yes you could record externally in 4k as well but that is a lot more difficult and expensive to do right now.
 
Yes, by going to 200Mbps in ETC you're effectively at 8x the data rate on the central region compared with cropped 4K@100Mbps. It's a very good remark. However, with all-I you use the benefit of temporal compression, so on fairly static scenes the detail you can have will be limited. This whole thing demands to be tested, but you have a very good point, there is probably some real gold hidden under that tarp :)

Edmund
 
edmundronald said:
Yes, by going to 200Mbps in ETC you're effectively at 8x the data rate on the central region compared with cropped 4K@100Mbps. It's a very good remark. However, with all-I you use the benefit of temporal compression, so on fairly static scenes the detail you can have will be limited. This whole thing demands to be tested, but you have a very good point, there is probably some real gold hidden under that tarp :)

Edmund
Click to expand...

Temporal compression only matters when you have a limited datarate. That is how 50mbps IPB can look as good as 200mbps all-I. By shooting 200mbps you don't lose any quality or detail but the codec may be wasting bits. If one has the storage space it doesn't really matter if the codec wastes bits. Just let it throw a crap load of bits at every frame and never worry about the codec trying to figure out how complex each frame is and how many bits it should throw at the frame. All-I on the GH3 wasn't as good because it was only 72mpbs. That is bit starving the encoder for all-I. As long as the all-I codec has enough bits it will look amazing. 200mbps is more than enough for beautiful 8bit HD video. I used to use 200mbps mpeg2 as an editing format with Avid Liquid. Great format equal to ProRes outside of the 10bit support that is. Keep in mind Apple ProRes 422 standard only uses 117mbps for 23.976 1080p video. ProRes 422 HQ uses 176mbps and those are compressing 4:2:2 and 10bit. ProRes 422 standard at 59.94p 1080p would use around 300mbps but again remember that is for 10bit and 4:2:2. 200mbps 60p may be a tiny bit lower quality than using ProRes 422 but not by a whole lot once you factor in the less bits needed for 8 bit and 4:2:0 color.
 
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