21 votes

Why does my Canon 700D take so long processing when I take a long exposure?

To reduce the processing time for long exposures, you want to turn off Long Exposure Noise Reduction. However, you may not want to give up the benefit of LENR. Long Exposure Noise Reduction (LENR) is ...
Michael C's user avatar
  • 175k
8 votes

Why does my Canon 700D take so long processing when I take a long exposure?

It's not actually processing for most of that extra time. It is taking a second exposure with the shutter closed, for dark frame subtraction. This removes sensor-based pattern noise. Of course, there ...
mattdm's user avatar
  • 143k
7 votes

How to remove hot pixels with a dark frame?

Ideally, dark frame subtraction should be done with raw images before demosaicing. Then the resulting black spot is 1 pixel, and after demosaicing it will typically be invisible in the result due to ...
remco's user avatar
  • 3,161
5 votes
Accepted

What should I look for in a camera for shooting in bulb mode for astrophotography?

Regarding Bulb Mode If you use a wired remote there is generally not a time limit regarding the length of an exposure using bulb mode with most current DSLRs. Pressing the button, halfway or fully, ...
Michael C's user avatar
  • 175k
5 votes

Long exposure shots showing huge bright spot. What happened to my sensor?

I do not know that specific camera, but generally sensors will have a pattern of thermal noise which is not uniform. The "Long Exposure Noise Reduction" feature, if your camera has it, is intended to ...
Linwood's user avatar
  • 2,363
5 votes

Issues with dark frame subtraction: Dark frames adding "noise" and changing image color/tint

You misunderstand the purpose of dark-frame-subtraction. While it is a technique used to reduce noise, it only reduces noise that is consistently output from the sensor. Any read noise due to the ...
Itai's user avatar
  • 103k
3 votes
Accepted

At what exposure times do fixed pattern noise become apparent?

Shutter time is only one of many variables that affect when dark frame subtraction would be beneficial. There is no single answer to your question. Since what we call 'noise' is present in all ...
Michael C's user avatar
  • 175k
3 votes

Dark Frames for Long Exposure on a tracker?

Shoot (15 minutes) x (However many frames you want) → manually shoot one dark frame (15 minutes). You can take a manual dark frame by putting a lens cap on the lens before taking the shot. You're done....
Michael C's user avatar
  • 175k
2 votes

Black level unchanged after long exposure noise reduction

Noise reduction is concerned with maximizing the Signal-to-Noise Ratio (SNR) by differentiating between actual signal and signal created by noise. With a lens cap on the camera there is no signal in ...
Michael C's user avatar
  • 175k
2 votes

What should I look for in a camera for shooting in bulb mode for astrophotography?

To address the "for beginners" aspect of the question, most recent-generation Olympus Micro 4/3 cameras (which are mirrorless, not technically DSLRs) have a feature called "Live Bulb" which allows you ...
junkyardsparkle's user avatar
2 votes

How does in camera dark frame noise reduction work?

I am confident that the exact method used by each camera manufacturer is different and company-confidential. All manufacturers have a large vested interest in getting the maximum image quality using ...
chili555's user avatar
  • 712
2 votes

Issues with dark frame subtraction: Dark frames adding "noise" and changing image color/tint

Instead of reducing noise, the darkframe subtraction increased the noise- or rather, added some dark/monochrome noise. How long was your session? What was the ambient temperature? Was the camera at ...
Michael C's user avatar
  • 175k
2 votes

Issues with dark frame subtraction: Dark frames adding "noise" and changing image color/tint

A while back I tried some of these images and found that it was much more convenient to take a dark frame for a group of long exposures rather than sit and wait for a minute every time I took a minute ...
dmkonlinux's user avatar
  • 1,003
1 vote

Terminology - photos with lights on, lights off

I think "lit" and "natural light" are the two terms you're looking for in terms of distinguishing using lighting gear or not using lighting gear, if you don't light. A very ...
inkista's user avatar
  • 52.1k
1 vote

Issues with dark frame subtraction: Dark frames adding "noise" and changing image color/tint

Try turning on in-camera darkframe subtraction instead. The designers of the camera have insight into how to best mitigate noise because they have detailed knowledge of the sensor and the noise ...
Bob Macaroni McStevens's user avatar
1 vote

Why does a non-linear relationship exist between noise level (of dark frame) and ISO setting

Based on inspection of your "captured dark frames and their associated statistics" and some experience in document scanner technology, it appears that between ISO 400 and 200, Canon shifted away 2 ...
blekenbleu's user avatar
1 vote

What should I look for in a camera for shooting in bulb mode for astrophotography?

Some very good answers about long exposure times, but for astrophotography I thought it was worth adding another consideration - the rotation of the earth. If you're looking for star trails (https://...
ItWasLikeThatWhenIGotHere's user avatar
1 vote

Black level unchanged after long exposure noise reduction

There are many sources of noise in the CMOS imaging process. Fixed-pattern noise (FPN) refers to image noise caused by nonuniformity in the sensor. For example, differences in manufacturing might ...
Kevin Chen's user avatar
1 vote
Accepted

Long exposure shots showing huge bright spot. What happened to my sensor?

First, let's distinguish two kinds of noise. One is temporal random noise, such as thermal noise, photon shot noise, or electron shot noise in the analog electronics. These tend to follow Poisson ...
Carl Witthoft's user avatar
1 vote

Why does raising ISO make image quality appear lower even though my measurements suggest it shouldn't?

In this answer ISO, shutter speed and aperture are independent parameters. 1) Yes, setting ISO to a higher number will almost always lead to better SNR - because additional analog amplification ...
Euri Pinhollow's user avatar

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