Tuesday, August 20, 2019

Viewing the night sky in color with an Amcrest IP4M-1026

So called Starlight cams seems to be becoming a thing so I thought I'd see what is possible with a camera I already had. You can look at my video Night sky Aug 10th 2019 and Night sky Aug 9th 2019 to see what I'm talking about here.

With a few simple tests the Amcrest IP4M-1026 seemed to have the best low light video and the widest view. Mainly I wanted to try and capture some of the neighborhood's fireworks displays.  My first test with pretty much default settings came out OK with lightning.  It seemed to me it switched to night view earlier than it needed so I played with the options to get the video linked above.

I was surprised how much I could make out by just moonlight. It basically looked like what I would see looking out the window.


Below are the setting I used. You might be able to tweak this a bit further with experimenting but I'm happy with the results. Though the fireworks capture was pretty much a bust as they were a lot more subdued this year and the few that did make it into were mostly blocked by the trees. Thinking now I'll add another cam to close to double the 118 degree view. Note I also did a test with a GW5747MIC 5MP Optional TWO-Way Audio PoE IP Camera 1.9mm 160° Wide Angle Night Vision Sony Starvis HD 1920P Security Mini Dome 5 Megapixel Built-In Microphone and Micro SD slot, Audio in/out Recording but the view was not only no wider but not as good in low light.

Added video without the Moon to show when it is too dark to even see out you can still see the horizon glow of Austin, the planets, at least 1 star, the bard and trees. Here are compare pics from my cameras that catch bits of the same view all from the same time, 8/21/2019 at 10PM local despite what some of the on screen timestamps say.

Screen grab from the posted video
Snapshot directly from Blue Iris
Snap shot from Reolink RLC-411WS (5MP Version) of west end of barn in sky pic
Snapshot from RLC-511W across south deck. Note plane from video and above Amcrest snapshot is just above far horizon. 

Snapshot from Reolink RLC-511 (non WiFi) of mid drive. Ton of IR down here so any bits not lit are hard to see.
From Hikvision DS-2CD2035-I overlooking the pool area (not currently up). Note when the moon is up you can usually see the horizon in this view.
Just in case you think the Amcrest is optimized for night, here is a snapshot from high noon.
Amcrest IP4M-1026 snapshot of sk with sun skirting top of frame.


Sunday, August 11, 2019

Doing the math on pixels per inch at a distance for your cam

Seeing a lot of posts where people are talking up 1080p cams with wide angle. Let's do the math on that. There is a simple calculator online to get the width of the area being viewed by a cam with a given view angle. For example let's take my old work hours the Foscam 9800 series that is 720p and 70 deg view angle.

So at 20 feet the view width is 24.4 feet or 293 inches. 720p resolution is actually 1,280 pixels so when we divide the pixels by the view width you get  4.3686 pixels per inch. So a face, about 6 inches wide will be 26 pixels across at 20 feet with this cam. 40 is considered to be the min. So even with the best lens focused for 20 feet this is still not going to cut it.

For convenience I worked up the charts below from my compare sheet. Note these charts assume the camera is focused for the target distance and not the upscaled resolution some cams advertise. Despite claims, outdoor fixed focus cams seem to be focused at around 20 to 30 feet. You might get a "decent 2X screen grab" of targets within +- 10 feet of that. Of course for a large range of  depth you really should look at a camera with autofocus like the Reolink RLC-411WS I've tried. Though it has had the occasional glitch as well. For long distance something adjustable like the Microseven 6-22mm 3MP Manual Zoom Varifocal Len HD 1080P.







Not those are best case numbers under perfect conditions. While 7 pixels per inch is bare min 14 is the more accepted min. If I change the wanted pixels per inch to 14 the last chart becomes

Note 12 degrees is a fairly extreme telephoto lens in the range of 22mm
70 is standard though up to 90
between 90 and 130 is often called wide angle
180 to 360 are often called 360 view cameras

For a more indepth info look here.