#apertus IRC Channel Logs

morning folks!

off for now ... bbl

hi Bertl

glad you liked it

parasew said you are going to deliver the first 20 prototypes these days?

off for a nap ... bbl

the prototypes are being hand assembled, lots of electronic components to be placed

but for 20 units automated assembly is just too expensive per unit

depending on how many units crowdfunding backers/voucher holders want from this hardware generation maybe around 100 units already

where do I need to sign up :-)

there is a preorder notification list to sign up for here: https://www.apertus.org/axiom-beta

and an explanation of phased paiements here : https://apertus.org/axiom-beta-phased-payments

hehe :-)

what do you mean with "goals which need to be achieved for testing, hardware and software" in particular?

what are you going to test with the firts prototypes

is it hardware issues, thermal managment

we know that the hardware works

so that we will do

for color calibration

and hdr

dead pixel compensation

designing a proper log curve

etc.

https://www.apertus.org/axiom-beta-roadmap

camera hosted websites to control the camera

histograms, curves, heat and power consumption related guis

looking at https://www.apertus.org/sites/default/files/dr-illustration-v03.png

which is symmetric with respect to dark and bright colors?

I guess it will be possible to more closely match the response of film

because you can only reset bright pixels you need to have a large exposure time for all, so you can not bend the curve upwards (make it concave)

sure, you can mimic any curve in post

but for the shown piecewise linear curve one has high dynamic for dark pixels but low dynamic for bright pixels

I highly doubt the detail loss will be noticeable

wakalixes: The output of the camera curve should attempt to distribute equal bits per stop as a general decent concept.

yes, and the piecewise curve approximates exactly that

wakalixes: What do you mean amplified noise?

alexML: Have you seen any PW imagery yet?

you can fine-tune the two knots on the piecewise curve

wakalixes: The long and short of it is that in an 'ideal' world, of course we would only have a linear signal that grabbed _all_ the data for a 50 stop range, but that isn't realistic.

wakalixes: So the question is, what is a reasonable trade off? We obviously desire the latitude, but we also want to keep a decent degree of proper perceptual adjustment in post. That implies attempting to balance out the bits with "what we see", hence the log2 concept.

Because that wouldn't result in a very balanced perceptual equivalence.

Thinking.

wakalixes: yes, the quantization noise gets amplified, but I bet the shot noise is much higher, so you won't notice it

I am not quite seeing the 'amplification' issue though.

wakalixes: Technically there won't be any multiplication of data, at all.

wakalixes: So let's assume we can get a decent PW curve that grabs 14 stops (optimistic perhaps)

wakalixes: What noise are you speaking of? I'm not quite following you on that point.

so if we look at the linear response, we can do the following in post:

So if we slide the exposure up, there isn't any more noise

we just run out of head room.

so yeah, this noise gets amplified when you go from piecewise to linear

I suppose you could say that we are losing accuracy

but I still don't necessarily see how we are generating noise.

We are losing accuracy in the sense that the photosites might be forced to be quantized into a unit they don't belong, but in the end, such is the tradeoff.

i mean that the SNR will be dependent on the slope of the piecewise curve, i.e. for dark areas larger and for bright areas smaller

afk for a bit

So I'm still not entirely sure of the concern I suppose.

My point would be, YES we are trading off that post production versatility. That's a rough one. You can't overexpose your image or underexpose too badly.

so the ADC will give a response curve with steps of the size of the LSB

Ideally I'd like to see something specifically tuned to the number of stops.

and andoing the piecewise slope will decrease the step size for dark areas but increase them for bright

undoing

hence the noise from the ADC several bits will be "amplified" in the bright

wakalixes: FYI, Nikon compresses the highlights in the same way when saving NEF

look for " An aside on "lossy" NEF compression: "

I mean it isn't terribly practical to shoot motion pictures or still pictures with a nine stop latitude.

that is true

(Not quite. Some of us still have emotional scarring from shooting extremely thin latitude reversal stocks.)

I am asking because I know the sCMOS sensor CIS2521 (I was mentioning this one recently)

wakalixes: What are the dimensions and linear latitude range?

Oh interesting.

and on top of all an ultra-low-noise readout

What are the dimensions?

http://fairchildimaging.com/category/product-category/focal-plane-arrays/scmos

mostly looking at dark and bright frames

wakalixes: No dimensions on that page.

alexML: That's odd.

there seem to be two parallel readout circuits, with slightly different electrical characteristics

so, many of those artifacts appear because of the differences between the two circuits

I'll try doing that in software

but there is LTN4625A with 4608 (H) x 2592 (V) pixels (presented in Feb 2015)

alexML: Not sure that is ideal colorimetry wise. Would be mroe prudent if it can be equalized in hardware.

2560 Bayered????

it is APS-C

troy_s: there is an offset that can be adjusted in hardware

alexML: Interesting.

but other than that, all the other parameters look common

what I don't like is that, on a test gray frame, after subtracting a dark frame, only half of that offset is corrected

hm, histogram matching says a plain offset is enough, no difference in gains (that's good)

good night