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Andrew Reid

An adventure into the Panasonic GX85/80 begins - and a look at the Leica Nocticron for Micro Four Thirds

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2 hours ago, Mattias Burling said:

A cropped sensor doesn't affect exposure or dof, so the conversion is pointless imo.

Hi Mattias

Whereas you are correct that a cropped sensor does not affect exposure, you are wrong about it not affecting depth of field.

I think you know that a small sensor video camera (ie a typical ENG camera) cannot achieve narrow DoF, whereas a FF DSLR can achieve narrow DoF. 

So if I set up a MFT and put on it a 50mm manual lens (no sb) and measure the light with a light meter to be 5.6 at ISO 200 at 1/50, I set the lens and camera up with those settings and achieve perfect exposusre.  I then take that lens off and put it on a FF DSLR next to the MFT camera, leave the lens settings the same and set up the DSLR with those ISO and SS settings, I will also acieve perfect exposure.

This is because f stop is a ratio between aperture and focal length, so sensor size does not influence exposure, as you stated.

https://en.wikipedia.org/wiki/F-number

However, as the MFT sensor is smaller than the FF DSLR, it has a greater DoF for the same focal length when compared to a FF camera. So when you look through the view finder of the FF DSLR using exactly the same lens and settings as we used on the MFT, you will see a narrower DoF.

This is explained here : https://en.wikipedia.org/wiki/Depth_of_field

This quote from the article summarises it.

Quote

Moreover, the larger the format size, the longer a lens will need to be to capture the same framing as a smaller format. In motion pictures, for example, a frame with a 12 degree horizontal field of view will require a 50 mm lens on 16 mm film, a 100 mm lens on 35 mm film, and a 250 mm lens on 65 mm film. Conversely, using the same focal length lens with each of these formats will yield a progressively wider image as the film format gets larger: a 50 mm lens has a horizontal field of view of 12 degrees on 16 mm film, 23.6 degrees on 35 mm film, and 55.6 degrees on 65 mm film. Therefore, because the larger formats require longer lenses than the smaller ones, they will accordingly have a smaller depth of field. Compensations in exposure, framing, or subject distance need to be made in order to make one format look like it was filmed in another format.

So this is why lenses designed for MFT are smaller than an equivalent lens for FF. Sensor size compensates for absolute focal length ie a Panny 12-35 is equivalent in FoV to a Nikon 24-70 FF lens, but at the cost of shallow DoF.

Unfortunately this means that however good the Nocticron is, it can only achieve the minimum depth of field of a FF equivalent lens set at f/2.4 so it is very unlikely that the subject seperation will be as good as the Noctilux.

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3 hours ago, John Matthews said:

1) Having a stabilised, sharp manual focus preview REALLY helps getting a lock-on quickly with older lenses.

2) It's a shame I can't keep the magnified view during focus AFTER half-pressing the shutter or starting a video recording.

5) Audio sounds like there's a faucet running in the distance whenever IBIS is on. Really, it's only good for syncing in post, I imagine.

So far, I'm enjoying it and the GX80/85 seems to be a great camera for both stills and video.

Focal length = angle of view, Perspective = camera to subject distance, F-stop = depth of field, T-stop = light coming into the lens and hitting the sensor

What makes a lens great = high micro-contrast, high sharpness across the field, low distortion, round bokeh balls, low chromatic aberration, no vignetting, and maintains colors, easy-to-use, durable. Seemingly mathematical, but if you like the look, you like the look. It's more subjective than people think.

Excellent points, John, Thank you so much for sharing. My problem is that point (2) kills the benefit of (1). Practically, with a MFT camera including this GX80/85 the only way to record video is: focus - shoot - stop - refocus - shoot and stop. You cannot adjust focus precisely during video recording: no magnification for MF, and unusable (shimmering hunting) AF. The 4K image quality is great, but the ergionomics on Panasonic cameras for video recording is absolutely not my style because of these reasons. They are so close: why the hell they don't buy Sony PDAF 4/3 sensors into their cameras and add magnification with a firmware update? This is beyond me. 

BUT, in this article Andrew pointed out that the GX80/85 outputs clean HDMI that can be used by an external recorder. A decent external recorder definitely has excellent focus peaking and MAGNIFICATION WHILE RECORDING, therefore this limitation of the GX80/85 and all other MFT cameras is mitigated. At least a workaround solution to the accurate-manual-refocus-while-recording problem; Hmm, I like the idea. Blackmagic Design Video Assist 4K 7" 1920x1200 XLR recorder is only $900 + GX85 with excelent IBIS and 4/3" large sensor is only $800; total is $1700, not a bad deal. Thank you, Andrew,  for the excellent hint/suggestion/idea. Anyhow, I am waiting for the hopefully-forthcoming "4K edition of Sony A5100", then I'll make my decision.  

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16 minutes ago, Miklos Nemeth said:

Excellent points, John, Thank you so much for sharing. My problem is that point (2) kills the benefit of (1). Practically, with a MFT camera including this GX80/85 the only way to record video is: focus - shoot - stop - refocus - shoot and stop. You cannot adjust focus precisely during video recording: no magnification for MF, and unusable (shimmering hunting) AF. The 4K image quality is great, but the ergionomics on Panasonic cameras for video recording is absolutely not my style because of these reasons. They are so close: why the hell they don't buy Sony PDAF 4/3 sensors into their cameras and add magnification with a firmware update? This is beyond me. 

Have you tried getting used to focus peaking? 

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3 hours ago, Miklos Nemeth said:

Excellent points, John, Thank you so much for sharing. My problem is that point (2) kills the benefit of (1). Practically, with a MFT camera including this GX80/85 the only way to record video is: focus - shoot - stop - refocus - shoot and stop. You cannot adjust focus precisely during video recording: no magnification for MF, and unusable (shimmering hunting) AF. The 4K image quality is great, but the ergionomics on Panasonic cameras for video recording is absolutely not my style because of these reasons. They are so close: why the hell they don't buy Sony PDAF 4/3 sensors into their cameras and add magnification with a firmware update? This is beyond me. 

I've been combing through these forums for a couple of years. One thing is certain, there's no perfect camera. I don't know why they chose to turn off magnification when recording starts and it's probably just one of the many limitations this camera offers. This camera DOES offer compactness (one major feature of MFT, yet possibly something even the future GH5 can't offer), great IQ, and cutting edge IBIS for a crazy-good price. Compactness usually sacrifices ergonomics, usability, and build. It's not a DSLR you can "pound nails with," but in many ways, it's a swiss army knife... not the best at one thing, but not bad at anything- just "competent." I also noticed the ergonomics and build when I first picked it up, but I quickly forgot and adjusted after just a few days. Concerning firmware, we can hope... but Panasonic isn't Fuji.

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51 minutes ago, mercer said:

So you can't just double tap the screen again, while recording, for magnification to reappear?

Nope. Not with the current firmware... but maybe there's something I'm not doing right. It seems there are a WIDE variety of ways (touch, buttons, wheels) to punch on focus with manual lenses BEFORE but not WHILE filming. What I would like is to turn off half button shutter focus and use it for magnification before or during... can't seem to do it.

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5 hours ago, DevonChris said:

Hi Mattias

Whereas you are correct that a cropped sensor does not affect exposure, you are wrong about it not affecting depth of field.

I think you know that a small sensor video camera (ie a typical ENG camera) cannot achieve narrow DoF, whereas a FF DSLR can achieve narrow DoF. 

So if I set up a MFT and put on it a 50mm manual lens (no sb) and measure the light with a light meter to be 5.6 at ISO 200 at 1/50, I set the lens and camera up with those settings and achieve perfect exposusre.  I then take that lens off and put it on a FF DSLR next to the MFT camera, leave the lens settings the same and set up the DSLR with those ISO and SS settings, I will also acieve perfect exposure.

This is because f stop is a ratio between aperture and focal length, so sensor size does not influence exposure, as you stated.

https://en.wikipedia.org/wiki/F-number

However, as the MFT sensor is smaller than the FF DSLR, it has a greater DoF for the same focal length when compared to a FF camera. So when you look through the view finder of the FF DSLR using exactly the same lens and settings as we used on the MFT, you will see a narrower DoF.

This is explained here : https://en.wikipedia.org/wiki/Depth_of_field

This quote from the article summarises it.

So this is why lenses designed for MFT are smaller than an equivalent lens for FF. Sensor size compensates for absolute focal length ie a Panny 12-35 is equivalent in FoV to a Nikon 24-70 FF lens, but at the cost of shallow DoF.

Unfortunately this means that however good the Nocticron is, it can only achieve the minimum depth of field of a FF equivalent lens set at f/2.4 so it is very unlikely that the subject seperation will be as good as the Noctilux.

Take a picture out of a magazine. Take a pair of scissors. Cut out a x3 crop piece. Did the dof change?

 

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38 minutes ago, Mattias Burling said:

Take a picture out of a magazine. Take a pair of scissors. Cut out a x3 crop piece. Did the dof change?

 

I think you and I must be talking about different things. 

You seem to be saying that a crop sensor only takes a small part of a scene (ie taking a pair of scissors to it) whereas in actual fact it records the whole scene but with a narrower field of view, which is then subject to the physics that creates a deeper depth of field that I mentioned above.

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To simplify the discussion: a 42.5mm/f1.2 lens on MFT has the sane DoF as a 42.5mm/f1.2 lens on FF, but a narrower angle of view.

To obtain the same DoF AND angle of view of a 42.5mm/f1.2 MFT lens on FF, you'll need a 85mm/f2.4 lens.

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1 hour ago, Mattias Burling said:

Take a picture out of a magazine. Take a pair of scissors. Cut out a x3 crop piece. Did the dof change?

 

If you blow up the image 3x (because when you want to compare images, you compare them at the same size), the dof will change. Because DOF is a concept that relies on the Circle of Confusion.

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Quote

To simplify the discussion: a 42.5mm/f1.2 lens on MFT has the sane DoF as a 42.5mm/f1.2 lens on FF, but a narrower angle of view.

Actually this is wrong!

A 42.5mm f/1.2 lens on MFT has the same depth of field as a 42.5mm f/2.4 on FF as well as a narrower field of view as you mentioned.

So if you want the depth of field that a FF f/1.2 lens gives you on MFT, you will need a f0.6 lens

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Read this, http://toothwalker.org/optics/dof.html, and understand it.

 

And btw, conversions make all the sense in the world. A 36x24 proyection with a 85 2.4 lens will give the same image as a 18x12 proyection of a 42.5 1.2. lens. The total amount of light will be the same, and both images when magnified to the same size, will look almost identical (except the smaller format will look proportionally shittier, blurrier, which you might like if you are going for the hipster look)

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1 hour ago, Nikkor said:

 

If you blow up the image 3x (because when you want to compare images, you compare them at the same size), the dof will change. Because DOF is a concept that relies on the Circle of Confusion.

No the dof doesn't change, only your perspective on it.

A 50mm f1.8 is always a 50mm f1.8 no matter what. The only difference is the crop. And a crop is exactly the same thing as cropping in post with a pair of scissors.

I know this is a touchy subject for some, and I personally don't see any point what so ever to talk about "equivalents" so I will leave it at that.

 

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17 hours ago, Brian Williams said:

 

You should be shooting your video in manual. AF for video is for grandparents shooting clips of their grandkids on their iPhones.

This is the most ridiculous post of 2016 on Eoshd. 

AF like the one on the 1DX2 is a real game changer for anything like fast street shooting, tracking, Gimbal use, and so on. 

It as never been used before professionally because it sucked in video. 

It is the same in photo. Before people used to shoot manual, since the AF is good all pros shoot with AF. Go see a pro sport photographer and tell him only grand ma should use AF. You are a real idiot :) 

@Andrew Reid of course the lens is about the look you are right. But the subject isolation and DoF is also a criteria. I am not saying it does everything but it is something and on this point M43 is not FF. I am fine with it though, my biggest concern with M43 is more for landscape stills. I agree that the subject isolation can be good enough on m43 especially with the right lenses.

did you try the new 42.5 f1.7 apparently it is almost as good and 3 times less the price. Could be a great cheap combo with this camera. And the new OIS on it is a killer with the dual IS apparently. 

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Andrew:

I'm curious about the HDMI-out functionality.  Could you elaborate more?

1) For instance, when a clean signal is outputting via hdmi, does the rear LCD screen shut off or does it stay on so we can see our settings and make changes to the settings?

2) If we want on-screen overlays on the hdmi-out signal is this possible?  If so, is the output windowed (like the A7S) or is it full 16x9 (like the 7D Mark II) or is it like a hybrid arrangement (i.e. RED, Canon C300II)?

3) Does hdmi-out remain active as we are recording internally?

 

For my uses I like using a larger external monitor so being able to record internally and still get an hdmi-out feed with overlays in full 16x9 is important to me.

 

Thanks

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I'm bowing out of this discussion as it is clear that some people don't understand the principles.

The link that @Nikkor provided explains it perfectly, and mathematically supports the argument that sensor size does influence DoF.

<edit>

This is the important part of the article in the link :

Quote

Although the perspective, composition and F-number are the same, the depths of field differ greatly. The digital image has 5 meters of DOF, the 35-mm image barely 1 meter. This is due to the very short focal length of the digital camera, which outweighs the smaller COC criterion. The infinity blur in the above table denotes the blur disk diameter, on the film/sensor, of a distant point. So, in addition to the larger DOF, the digital image also has less background blur. (Both absolute and relative.) On a 20×30 cm print, the blur disks would measure 0.43 and 1.8 mm, respectively. These characteristics of miniature-sensor digital cameras are considered an advantage in landscape photography, which often requires a large DOF, but it becomes a nuisance in portraiture when the photographer tries to blur the background. This is often just not possible, certainly not with cell phone cameras which usually have an even smaller sensor than in the shown example.

</edit>

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Just a correction in the article about the 1080p codec:

"The 4K codec is 100Mbit/s 30/25/24p so same as the GH4, however the 1080p codec is at a lower bitrate. 28Mbit/s in 60p and 20Mbit/s in 24p. This makes for some nice small files but there’s no ALL-I or high bitrate option like on the GH4. Just shoot 4K for best quality 1080p delivery, or an external recorder."

If you shoot in AVCHD at 24p, you get 24Mbit/s. Not 20 Mbit/s. Still 4k is best. What are your settings in the Standard profile?

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