Sigma Fp review and interview / Cinema DNG RAW

[mercer]

1 hour ago, rawshooter said:

I can also warmly recommend the Tokina 28-70mm/2.8 which is a bought-up and continued Angenieux design:

https://cameragx.com/2018/04/11/the-truth-about-the-angenieux-28-70-af-zoom/

Great lens. I briefly had it a couple years ago but had to sell it. I've been looking for another good copy ever since. @JordanWright has some great work with it shot on his P4K.

[paulinventome]

On 1/18/2020 at 5:23 PM, cpc said:

You can do various transforms to shrink the ratio between extremes, and this will generally reduce ringing artifacts. I know people deliberately gamma/log transform linear rendered images for rescale. But it is mathematically and physically incorrect. There are examples and lengthy write-ups on the web with what might go wrong if you scale in non-linear gamma, but perhaps most intuitively you can think about it in an "energy conserving" manner. If you don't do it in linear, you are altering the (locally) average brightness of the scene. You may not see this easily in real life images, because it will often be masked by detail, but do a thought experiment about, say, a greyscale synthetic 2x1 image scaled down to a 1x1 image and see what happens.

Yes, you're right of course i think on a practical level in those cases it's easier to take the hit for not being 100% physically accurate as a scale is usually pre processing before doing linear comp work (or after). It's nice to run energy conserving convolution filters of lens aberrations over CG footage, works really well, better than blurs.

On 1/18/2020 at 7:53 PM, rawshooter said:

To give an example, we might have an edge of a red object against a grey object. In the Bayer pixels representing the red object, red values would be high, green and blue values would be low; in the Bayer pixels representing the grey object, red, green and blue values would be about the same. But if we isolate the red matrix and only take the edge, then we'd see a high red value for the red object against a lower red value for the grey object. If we interpolate and scale, we'd average the two red values, which would be visually wrong - because we're (a) blurry the edge and (b) in the mix with the other blue and green values and their processing, create false colors.

Yes, these are the kinds of thought experiments i'm trying to wrap my head around. In the case of the edge case (ha pun intended!) even with the full RGGB bayer info would that situation be much different - if the missing pixel between the R and the R is a green - the missing red would still be interpolated. You can of course argue that the luma of the G in that position would be the basis for that interpolation and therefore more accurate. If you scaled the channels down first then output that RGR edge - it would be softened - in your example that applies if you scale up, you are adding data. But scaling down you are removing and averaging. So the thought experiment is what is the best scale to do here - is it nearest neighbour or some kind of non sharpening scale as i can see edge issues with sharpening.

I must assume sigma has tested this if it is in fact what they're doing. 

I must also go back to the basic question i wonder if there's anyway just to get 6K out of this thing. Do we know which specific USB version it's running and what the data rate would be? Also isn't the Red patent to do with lossy compression? If you just do run length encoding on the stream does that not work?

I think sigma should open source the OS

On 1/18/2020 at 4:43 PM, Lars Steenhoff said:

Question, if you put the camera in M mode and you set the shutter speed to 50 why does my fp make the shot at 100?

So i've seen a case with the stills doing odd things with exposure, when switching between cine and stills and i am trying to match for testing. But after a reset it stopped. So i reported a bug but wasn't able to give steps to reproduce.

I got caught by having the camera in S mode with a manual lens yesterday - what's annoying is the screen is compensating. So i assume that the camera thinks there is a lens where it can adjust aperture thinks it's stopped the lens down for example and compensates on the LCD but the actual shot is exposed totally wrong. So the M mode is essential.

But it makes me wonder *why* the screen isn't showing an accurate preview of the exposure (and i had the setting on)

So there are some bugs. I've not been massively affected by a shutter lag though. Does it help if you turn off screen black out and also turn on the low previews mode?

cheers
Paul

[Lars Steenhoff]

In stills mode with exposure preview ln the camera is doing lots of things it should not be doing.

For example its adjusting the frame rate / display refresh rate when in low light ( lower frame refresh )

and in bright light faster refresh rate.

On canon cameras m mode is much easier to work with.

there the display refreshes faster in preview mode and makes the final shot with the same visual exposure.

Another thing that bugs me is at I cannot turn of noise reduction for the previews.  I want to see the shot without noise reduction. even when shooting in raw it noise reduces the preview image in camera

[rawshooter]

4 hours ago, paulinventome said:

Also isn't the Red patent to do with lossy compression?

Unfortunately not - while the RED codec is lossy, the RED patent much more broadly covers any kind of compression of raw/undebayered moving images.

[Andrew Reid]

Hopefully Sigma will read all of this before putting a firmware update out. I'll send them an email with all the annoyances and bugs in it.

[paulinventome]

1 hour ago, rawshooter said:

Unfortunately not - while the RED codec is lossy, the RED patent much more broadly covers any kind of compression of raw/undebayered moving images.

But if you compress the transport stream - like gzip or similar - that's not RAW compression, right? The RAW is still uncompressed. The Red patent is all about compressing the RAW before saving it out - i doubt you can patent compressing a transport stream - after all http2 is compressed like this too...

cheers
Paul

[paulinventome]

5 hours ago, Lars Steenhoff said:

In stills mode with exposure preview ln the camera is doing lots of things it should not be doing.

Yeah, one thing i've noticed is that if you have it set to X iso and Y shutter and then dial the physical aperture on the lens the preview lightens then slowly darkens. You can see the waveform doing it - like the screen tries to brighten then realises it's M mode and animates to the new display. It's odd because i cannot understand why anyone would code it like that. With an animation as well

5 hours ago, Lars Steenhoff said:

Another thing that bugs me is at I cannot turn of noise reduction for the previews.  I want to see the shot without noise reduction. even when shooting in raw it noise reduces the preview image in camera

Odd, i've not noticed that and i don't think the LCD is high enough res to show any noise. Is this all DNG or JPEG?

cheers
Paul

[Andrew Reid]

There's no noise reduction on/off switch in the menus so LCD is showing a JPEG or proxy still image with NR added. And it's a very clean sensor anyway, even at ISO 12,800 you have to zoom very very far into the image to see the slightest hint of noise.

I have tried every combination of setting to try and get the exposure to match between stills M live-view and final image when taken, and it's no go... Very strange as it's fine in Cine mode or with a lens that communicates aperture to the body. So I assume it is a bug where the lens aperture is unknown, and that will need a firmware update. For now, I do advise Auto ISO and Exposure Comp in M mode, or use A mode, as a workaround.

Update:

Actually since Exposure Comp (effectively ISO) does not work in M mode on any of the dials and can't be assigned (have to dive into menus for it), here is a better workaround when using lens with manual aperture and you want full manual control with matching LV / stills.

- Use S priority mode instead of M

- Set ISO to Auto and control it with Expo Comp.

- Set aperture manually on your adapted lens (aperture ring)

- Set shutter speed manually

That is pretty much it. Now the problem is gone.

[Lars Steenhoff]

After I take a shot, I zoom in to check focus, and at high iso I see a noise reduced mess, I would like to see the noise/ actual pixels.

Good to hear you send a bug report to sigma @Andrew Reid

[Andrew Reid]

On 1/18/2020 at 11:26 PM, rawshooter said:

I can also warmly recommend the Tokina 28-70mm/2.8 which is a bought-up and continued Angenieux design:

https://cameragx.com/2018/04/11/the-truth-about-the-angenieux-28-70-af-zoom/

It's a blazing lens. Glorious. Still totally undervalued. I got my Canon EF version for £200. The AF even works well on the Fringer Nikon Z adapter (pictured below) for stills. Not so much video as the AF motors are clunky and old, very noisy... Optically though, it's glorious.

 

[Lars Steenhoff]

1 hour ago, Andrew Reid said:

There's no noise reduction on/off switch in the menus so LCD is showing a JPEG or proxy still image with NR added. And it's a very clean sensor anyway, even at ISO 12,800 you have to zoom very very far into the image to see the slightest hint of noise.

I have tried every combination of setting to try and get the exposure to match between stills M live-view and final image when taken, and it's no go... Very strange as it's fine in Cine mode or with a lens that communicates aperture to the body. So I assume it is a bug where the lens aperture is unknown, and that will need a firmware update. For now, I do advise Auto ISO and Exposure Comp in M mode, or use A mode, as a workaround.

Update:

Actually since Exposure Comp (effectively ISO) does not work in M mode on any of the dials and can't be assigned (have to dive into menus for it), here is a better workaround when using lens with manual aperture and you want full manual control with matching LV / stills.

- Use S priority mode instead of M

- Set ISO to Auto and control it with Expo Comp.

- Set aperture manually on your adapted lens (aperture ring)

- Set shutter speed manually

That is pretty much it. Now the problem is gone.

Interesting workaround however I don't like auto iso, when I make a noise reduction profile in resolve I like the noise to be consistent and not change during the shot.

 

[Andrew Reid]

Indeed, but you don't need to do this trick for video as the exposure is consistent in Cine M mode. Only stills.

Unless you are doing a timelapse in stills mode or something?

[Lars Steenhoff]

Mm, I think your right, I got confused with video for a moment

[BTM_Pix]

2 hours ago, Andrew Reid said:

I have tried every combination of setting to try and get the exposure to match between stills M live-view and final image when taken, and it's no go...

Does it do anything at all when you change "Preview Exposure in M Mode" from on to off ?

Might it be a conflict with Brightness in the LCD Menu being set to Auto over riding it ?

A real downer if something as fundamental as that doesn't work properly.

[Andrew Reid]

I diddled with those two settings to try and coax it into behaving, but no joy!

I'd also like a feature in the next firmware to shoot a still while in Cine mode.

But they better fix the bugs first :)

[BTM_Pix]

14 minutes ago, Andrew Reid said:

I diddled with those two settings to try and coax it into behaving, but no joy!

I'd also like a feature in the next firmware to shoot a still while in Cine mode.

But they better fix the bugs first :)

I've just tried it on my SD Quattro with an m42 lens in case its a "feature" they carried over and it appeared to be behaving the same way you describe so I went in and out of Program mode and it started behaving itself as it should and was still cured after a reboot.

I've seen some reports of people having to dick around power cycling between aperture changes to get A mode to work on the SD Quattro as well when using m42 lenses. For "m42 lenses" read "manual lenses" as those are the only ones you can adapt to it of course !

Long shot that its an initialisation issue but might be worth a cycle around the modes.

Anyway, I'm off to find a wrench to remove the now stuck m42 to SA adapter on my Helios 44!

[Andrew Reid]

Just gave that a go... In and out of P mode and then a power cycle, unfortunately it is still behaving like a drunk midget. Literally the only time I can get taken shot to match live-view is in Cine mode or in Stills mode with Auto ISO.

I am using Nikon -> M mount -> L-mount adapter, lens is the old 55mm F1.2.

[BTM_Pix]

2 minutes ago, Andrew Reid said:

Just gave that a go... In and out of P mode and then a power cycle, unfortunately it is still behaving like a drunk midget. Literally the only time I can get taken shot to match live-view is in Cine mode or in Stills mode with Auto ISO.

I am using Nikon -> M mount -> L-mount adapter, lens is the old 55mm F1.2.

Its not the real Leica M to L adapter is it by any chance ?

That could be passing misleading bullshit back to the camera, it certainly does on occasion with my SL.

Be interesting to know if you put an M lens on it whether it would be any different.

Ditto if you got an F to EF adapter and then put it on via the MC21 ?

 

[Andrew Reid]

Just a dumb passive Novoflex adapter, no electronic contacts on it. I think when this camera comes to "guess" at the aperture it gets it wrong, as it obviously works fine when it knows the aperture (i.e. from L-mount lens with electronic contacts).

Tried MC-21 just now with manual focus Voigtlander Ultron 40mm F2.0... This lens reports aperture electronically so it worked.

MC-21 with any passive adapter like M42 ring or Nikon F to EOS ring, has the dreaded bug.

Sigma advertised the Fp with a lot of manual stuff, PL lenses, all sorts, so it's a bit strange they didn't see such an obvious thing in testing!

[paulinventome]

Turning the screen brightness from Auto appears to have made M mode slightly more reliable as @BTM_Pix suggests. So fixed shutter speed and fixed ISO and ramping through manual apertures appears to work better. It sill animates between brightness levels which i total don't understand why.

What i do notice though is in low exposures in stills mode the brightness flickers randomly. Does everyone see this? I have reported that as well

cheers
Paul