A Very Still Night…500 sec Exposure with the M8

[david strachan]

Advertisement (gone after registration)

This is with Summicron 50mm (1952) collapsible at f5.6, on Leica M8 (23,000 exp), 500 sec on Timer and Bulb , 160 ISO.  I could only guesstimate/view the focus on the birdbath….it is -4 to -5 EV.  It’s a pretty dark night with minor light from the house.  UV/IR filter. In camera settings contrast: medium high, colour sat: medium high, sharpening standard. Straight out of camera JPG, opened and reduced for l-camera-forum in LR 5.7. Of course the “dark slide” kicked in for 500 sec too.

I stopped the image after 500 sec, but will try some even longer exposures soon.

 

The image could do with minor crop and processing to get something pretty good, certainly.  The DNG is available for best file and processing.

 

It was a very still night…

 

Cheers  Dave S  

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[david strachan]

Here is the processed 500 second image from raw.

cheers  Dave S

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[fiftyonepointsix]

That is amazing! The CCD is not even cooled... This camera would be great on a telescope.

[fotoism]

David:

 

Have you noticed any heating-up issues with the sensor for such long exposures?

[david strachan]

Here is 1000 second exposure opened in LR and adjust for exposure only (-2.85 stops).

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

 

 

But the sensor seems out of focus, and spots appear...they look like dust and gunk on the sensor...but I'm sure they are not "dusts"

[david strachan]

Using the Summicron at f2.8 and 360 seconds shows good star trails (city night clouds),  Good even star trails, good colours and evenly lit trails, without spots and lumpy gain exposures.. The battery has lasted well with past couple of nights experimenting.  Make sure you start with a bright battery out of the charger.

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

 

 

 

But on magnification...there are random tiny spots...like dust on the sensor. This can happen at very long sensor exposure...I wonder what it is, and just why it occurs??

 

 

Cheers  Dave S

 

[fiftyonepointsix]

Advertisement (gone after registration)

Basically- there are two kinds of noise in a sensor. Noise that occurs as the signal is read-out, digitized, and acquired- essentially a constant per image. The other noise is "Dark Current" which is a function of exposure duration. This noise is not from photons hitting the sensor, but from sensor itself. This latter signal is subject to more non-uniformity within the sensor, some pixels are "hotter" than others. A 20-minute exposure- amazing that the image looks this good. Dark Current increases with temperature, and the CCD heats up as it is operated. Many cameras designed for long exposures use a cooler, often a thermo-electric cooler (TEC). I could see someone buying an M8 and modifying it with a TEC, would be cheaper than a 10megapixel camera designed for astrophotography.

[david strachan]

Thanks for your comments everyone.

 

Strange I didn't get the spots on the first image at 500 seconds.

 

The star trail noise reduction certainly gives a very smooth background in long exposure with the M8.  Not lumpy with tonal variations, like other digital sensors I've used for star trails. However on extreme magnification the trails do show variations in gain with bright points joined with fainter points. Film (slide) still remains the best,IMHO, for star trails as the background stays ultra smooth, and the trails are perfect lines; star colours are better too.

 

Fiftyonepointsix's comments on the noise are very relevant, thanks Brian.  But I suspect the black spots are due to noise reduction, rather than overexposed pixels.  I just don't know though...

(Reckon you are right could make a good telescope camera...maybe too heavy though.)

 

Again thank you and fotoism for your thoughts. I will do some more experiments in due course...perhaps some ghost pictures..

 

cheers  Dave S

Edited September 14, 2015 by david strachan