Is this night photography coloured dot distortion from my sensor?

SirTomster · 12-07-2019, 09:52 PM

I was checking in Photoshop and I did not see hot pixels in this image.

Just stars.

I have seen plenty of Hot Pixels in my images because I love nightscapes. Where are you seeing them?

**Craigbob** · 01-10-2020, 03:10 PM

Originally posted by stevebarnes

Wow guys! What a lot of input. Thank you. Here's a bit of clarity:

A. I wasn't using long exposure noise reduction. Does it affect RAW files? If so, I must reconsider.

B. I've heard of using a dark frame subtraction. I'll have to look up how to do this on my K-1. Any references appreciated.

C. I used two lenses in this shoot. I believe I started with my Samyang flat 14mm f/2.8. It's this lens that the camera always thinks is 15mm. I should post another topic about this to see what people have to say. (advice, opinions?)

D. The other lens is my (made for K-1) Pentax D-FA 24-70 f/2.8. I must confess I thought the image from the prime lens was much superior. I use the 24-70 a lot for dog photography (fourfootfotos.com) and for portraits. It is wonderful on auto-focus compared to my other lenses, and produces a consistently nice image.

E. I'm a Ubuntu Linux devotee (please don't run away). After an injury that left me unable to work and took my house, I learned to week with open-source software. I use Darktable and GIMP. I also have RAW Therapee, but it's very technical, and I'm still learning it when I have time (yes, and a million other things too).
Whilst Darktable is quite amazing, offering drawn masks, parametric masks and other goodies Lightroom doesn't, I still haven't got Chromatic Aberration working properly! I need to get some expert advice I think.

I must download the images stevebrot produced! Thank you so much Steve.

Lastly, as a small VICTIMS fur my K-1 photography, I've been asked today to be a featured photographer at the Ballast International Foto Biennalli here in Australia. I'll be doing two (weekend) days during the 6 week festival of dog photography! It's a paid gig (only a few hundred each time at my own determination), but the amazing thing is the exposure. We have international exhibitors here, and people come from overseas and all round Australia to this amazing festival. I'll have my 4.5x3m black gazebo set up as a studio and my Pentax equipment will be proudly on show. I'll be advertised, and the organisers will take bookings for 15 minute time spots. My dog photography site is https://fourfootfotos.com. The Biennalli site is BALLARAT INTERNATIONAL FOTO BIENNALE |.

Dark Frame Subtraction is the same as Long Exposure Noise Reduction, the only difference is LENR is done in camera vs Outside the camera in SW like Sequator or Deep Sky Stacker. I highly recommend not wasting the time doing it while shooting which doubles the time for each shot, But taking a bunch of Dark frames of the same time and hopefully same temperature as your main images (Stick the camera in the fridge if it's cold outside). Then use those in Sequator od DSS to reduce noise.

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12-07-2019, 09:52 PM	#16
SirTomster Veteran Member Join Date: Mar 2014 Posts: 416	I was checking in Photoshop and I did not see hot pixels in this image. Just stars. I have seen plenty of Hot Pixels in my images because I love nightscapes. Where are you seeing them?

01-10-2020, 03:10 PM	#17
Craigbob Loyal Site Supporter Join Date: Mar 2017 Location: San Antonio, TX Photos: Albums Posts: 521	Originally posted by stevebarnes Wow guys! What a lot of input. Thank you. Here's a bit of clarity: A. I wasn't using long exposure noise reduction. Does it affect RAW files? If so, I must reconsider. B. I've heard of using a dark frame subtraction. I'll have to look up how to do this on my K-1. Any references appreciated. C. I used two lenses in this shoot. I believe I started with my Samyang flat 14mm f/2.8. It's this lens that the camera always thinks is 15mm. I should post another topic about this to see what people have to say. (advice, opinions?) D. The other lens is my (made for K-1) Pentax D-FA 24-70 f/2.8. I must confess I thought the image from the prime lens was much superior. I use the 24-70 a lot for dog photography (fourfootfotos.com) and for portraits. It is wonderful on auto-focus compared to my other lenses, and produces a consistently nice image. E. I'm a Ubuntu Linux devotee (please don't run away). After an injury that left me unable to work and took my house, I learned to week with open-source software. I use Darktable and GIMP. I also have RAW Therapee, but it's very technical, and I'm still learning it when I have time (yes, and a million other things too). Whilst Darktable is quite amazing, offering drawn masks, parametric masks and other goodies Lightroom doesn't, I still haven't got Chromatic Aberration working properly! I need to get some expert advice I think. I must download the images stevebrot produced! Thank you so much Steve. Lastly, as a small VICTIMS fur my K-1 photography, I've been asked today to be a featured photographer at the Ballast International Foto Biennalli here in Australia. I'll be doing two (weekend) days during the 6 week festival of dog photography! It's a paid gig (only a few hundred each time at my own determination), but the amazing thing is the exposure. We have international exhibitors here, and people come from overseas and all round Australia to this amazing festival. I'll have my 4.5x3m black gazebo set up as a studio and my Pentax equipment will be proudly on show. I'll be advertised, and the organisers will take bookings for 15 minute time spots. My dog photography site is https://fourfootfotos.com. The Biennalli site is BALLARAT INTERNATIONAL FOTO BIENNALE \|. Dark Frame Subtraction is the same as Long Exposure Noise Reduction, the only difference is LENR is done in camera vs Outside the camera in SW like Sequator or Deep Sky Stacker. I highly recommend not wasting the time doing it while shooting which doubles the time for each shot, But taking a bunch of Dark frames of the same time and hopefully same temperature as your main images (Stick the camera in the fridge if it's cold outside). Then use those in Sequator od DSS to reduce noise.