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Messages - tesla500

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Chronos User Discussion / Re: New 3350 mAh battery
« on: June 16, 2020, 12:34:23 AM »
I'm curious to see too! I don't know of any of these batteries, other than the (obscenely expensive) OEM Nikon one, that actually meet their capacity spec.

When selecting a battery to ship with the camera, I ordered many different versions and tested their capacity. None of them met their stated capacity, for example, the included DSTE battery that comes with the camera claims to be 3Ah or something like that, and I measured it at 2.2Ah. Far from spec, but not far behind the Nikon one, and about 1/5th the price. The DSTE battery was selected because it was readily available, had good build quality, and had one of the better capacities.

When the camera is operated at low horizontal resolutions, the horizontal line readout period is reduced, and there is less time for the sensor's analog-domain correlated double sampling operation to complete. This causes the pixel black levels to be offset upwards, so black comes out as dark grey. This is all invisible to the user, the black calibration corrects for this increased offset automatically, but it does decrease the dynamic range as you mentioned. The offsets are variable across the 32 analog to digital converter (ADC) channels in the image sensor, so different amounts are subtracted from each column.

When the image is saturated to white, the ADCs are all clipped, and so output the same value. When the column offsets are subtracted from this clipped output, it results in this vertical banding you see, since some columns have more subtracted than others. I don't believe there is any significant improvement to be made here unfortunately, it may be possible to have some improvement in a future software update by optimizing the sensor register settings, but it's largely a limitation of the image sensor itself.

To answer your question on homogeneous exposure, if you stay below the point where the vertical banding starts to occur, a homogeneous light pattern illuminating the sensor should result in a homogeneous image output. This is an offset issue only, there should not be any significant variance of gains across columns.

The simplest way to remove this is to simply gain up the images enough that the darkest pixels clip to white. You could also use the digital gain option on the record settings screen, but this doesn't have particularly good granularity. Doing it in postprocessing would be the most accurate.

Chronos User Discussion / Re: Accuracy of Chronos 1.4
« on: May 26, 2020, 01:43:01 AM »
Hi jbehler,

The frame period is internally quantized on 10ns increments, and the accuracy of the period/frequency is +/- 50ppm based on the internal clock's tolerance.

The exposure time is internally quantized on the image sensor's horizontal line readout period. The exact value is a little bit complicated to calculate, but it's approximately the frame period divided by the frame height in pixels. For example, say your frame period is 1ms (1000fps), and you're at a resolution of 1024 pixels. The horizontal line period is somewhere close to:

0.001 / 1024 = 976.6ns

So the ultimate exposure time will be a multiple of ~976.6ns periods, whichever is closest to the set exposure time.

You can observe this behaviour on an oscilloscope if you set frame sync output on one of the triggers. This signal active when the image sensor is actually exposing.

Let me know if you need any more info.


Chronos User Discussion / Re: Videos saved but gone
« on: May 26, 2020, 01:01:26 AM »
Hey Martin,

I had thought of a few things to check here, just to cover all bases.

  • Does your eSATA device have multiple partitions on it? If you selected a different partition than expected when selecting the storage device, the file may not be where you expect. If this other partition is something your PC's OS can't see (Like EXT3 from Windows), this other partition may not show up.
  • It is theoretically possible that, due to a bug, the files got saved onto the camera's OS card (microSD in the bottom of the camera), although this shouldn't be allowed by the user interface and underlying API. You could check to see if the files are on the OS card. You'd need to check both the FAT32 and EXT3 partitions that are present on this card.
  • [The d'Oh! one...]Was there any other save media inserted, such as an SD card? Could the files be on that media?

In addition to the file browser, another safety check that could be relatively easily added is to have the API check that the file was successfully written and is a reasonable size, and throw a warning if something doesn't seem right.


Chronos User Discussion / Re: 1.4 Boot problem
« on: May 12, 2020, 01:30:08 PM »
Does the power LED flash red just before the camera turns itself off? This indicates the PMIC watchdog thinks the main CPU has crashed, and is about to power it down. You might try reflashing the OS card with the latest software, as seen here

I would recommend a maximum ambient temperature of 40C. You can check the internal temperature on the About tab in the Util window, as long as the System and Image Sensor temperatures stay under about 70C you should be fine.

The camera has over-temperature protection, it will simply turn off if it gets too hot, but the image quality will degrade slightly while it's hot. The warmer the sensor, the higher the image noise. This isn't permanent, it will go back to normal when it cools down.


You can use the m2 SSD on the top of the camera and they may not cover the screen

Good idea, did you make a setup using one of these?

This is an SSD holder for the Chronos 1.4 and 2.1-HD. This accessory is invaluable when shooting DNG on the go; save speed is vastly improved compared to an SD card. The camera can write about 60MB/s to a SATA SSD instead of ~12MB/s to most SD cards. DNG saves at about 12FPS on the 2.1-HD and about 18FPS on the 1.4, at full resolution.

We plan to offer this for sale in our store eventually, but you can 3D print one right now! The attached models have been updated from the pictures shown, the SD card opening was widened so you can easily grab an SD card with your fingers instead of needing pliers to remove it.

We're in the process of ordering custom versions of the eSATAp cables that have a short cable length to avoid the need to coil up the extra cable.

Items you'll need

3D Printer to print the SSD cage (see attached files)

3D Print Instructions
This file has been tested on the Makerbot Replicator 2X
Recommended settings:
Print with raft, raft expansion 12mm
Print with supports
Orient the part with the drive opening pointing straight up

We've been using these at Krontech for the last few months and these mounts are incredibly useful, let us know how they work for you! One modification we were thinking about is centering the SSD above the camera. Currently, it overhangs the screen and makes it harder to see if you're looking from an upward angle. Thoughts?

Chronos User Discussion / Re: Post Chronos 2.1 clips here!
« on: February 17, 2020, 03:14:21 PM »
Had some fun over the long weekend vacuuming sawdust

Chronos User Discussion / Re: eSATA 3G interface
« on: February 13, 2020, 11:34:24 PM »
If you get an eSATAp cable, you can power the drive with just one cable

You can find an example of this cable here. We also sell these on our web store.

Chronos User Discussion / Re: Chronos 2.1 newbie questions and impressions
« on: February 13, 2020, 01:20:15 PM »
If you want to do a speed ramp, an Arduino would work, as would pretty much any programmable signal generator. You need to generate a TTL pulse for each frame capture.

You mentioned wanting to trigger a studio flash on every frame, which one did you have in mind? Most studio flashes I know of can only fire at a rate of a few Hz or maybe tens of Hz at most, with a low flash power setting, not the kilohertz rate needed for this application.

The battery gauge isn't the most accurate, and will decrease quite quickly at the start of discharge then slow down later. The battery should last 1 hour before the camera shuts down. I just tested mine and it ran for 1 hour and 5 minutes. How long were you seeing until the LED on top starts flashing red? It's possible your battery is defective.


Chronos User Discussion / Re: Post Chronos 2.1 clips here!
« on: February 13, 2020, 10:48:20 AM »
I've never heard of dB gain when talking about video recording, what does this mean exactly?

dB is decebel, a way to measure two relative signal strengths. In this case, 6dB of gain is equivalent to 1 stop, or a doubling of sensitivity. So 24db is four doublings, or 16x gain.

Thanks!I dont know what is the Max Setting, but 24dB Still looks more than ok!Looking great.

I find that 24dB gain on the 2.1 is about the same apparent noise as 0dB gain on the 1.4, the new sensor is really phenomenal with respect to noise!

Chronos User Discussion / Re: eSATA 3G interface
« on: February 13, 2020, 10:44:26 AM »
The eSATA interface is 3Gbps, so second generation.

Due to CPU limitations, the real-world write speed when saving DNG will be about 50-60 megabytes per second to a SATA SSD.

Chronos User Discussion / Re: Chronos 2.1 lenses
« on: February 12, 2020, 04:45:30 PM »
It may look rather weak but the C mount is quite strong. As Simon said I've used large 1kg+ lenses without issue, including dropping a camera with a ~900g F mount lens attached about 1.2m onto concrete, and the lens mount held up just fine.

Obviously, don't do anything remotely high-G with lenses like this, but for general use they will be just fine.

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