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Old 29-04-2018, 04:40 PM
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What is the best iso

First I post a link which I read today and am now somewhat confused.

I need to read it again but thought folk here might like it.

https://petapixel.com/2017/03/22/fin...c-range-noise/

In any event researching ISO today I went from an understading (flawed or not) that dslr cameras used a base iso and adjusted brightness by multiplying or decreasing based off that base iso...Further research suggested that base iso was indeed 100.
I was forming the view that shooting at 100 was therefore the best.
However reading all that is in the link has me confused.
He suggests noise may even be less at what I call very high ISO...so very confused.

So now I dont know which high or low...

So what should I use on my Nikon D5500?

Last night I stacked 120 frames ( 30 seco d each) thinking I was getting the Cats Paw but looking and processing I am not sure if I was on it..it is not in the image..It should have been as I was shooting at 200 mm thru my little 70 - 200 camera lens so I was confident it should have been in there...maybe the Moon was too bright...did I say I was at 3200 ISO?
The stack looked great but I cant get it to you via a post because I am having power problems (the panels are not charging my "office" batteries and I am desparatly trying to top them up with a 2.5 amp battery charger from Kmart via a little genny)... those in the house have banned me from playing on the lap top☺.

Anyways beside the point...does anyone have any views on the best ISO for dslrs and specifically the Nikon D5500 as apparently as the link mentions there are diffetent approaches depending on the camera.
And another question...perhaps yet another thread☺
Alex
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Old 29-04-2018, 04:56 PM
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Atmos (Colin)
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The D5500 is quite similar to my D7200 and I found the best ISO for the D7200 was 400.
I found for the D7200 that any ISO over ISO800 did nothing other than decrease the dynamic range without lowering the read noise any appreciable amount.

Now although they are different cameras with different but quite similar sensors, I'd say 200-800 is your best range. I middled that at ISO400.
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Old 29-04-2018, 05:26 PM
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Thank you very much for your help Colin.
You remind me that I did Omega Centuri at 400 iso the other night (Lobster night I think) and that seemed like a nice image.

I have quite a few to go over so I must have a long look at that one.

And I have yet to dither in an effort to improve.

Thank you very much for your reply.

I highly value your input particularly on this matter as rather than helping all I read today just complicated the matter and left me confused and timid.

Alex
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Old 29-04-2018, 06:43 PM
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Hello Alex,

I would also say that around ISO 400 (maybe 200 to 800) is a good choice and a reasonable compromise between noise and exposure time. See the ISO series assembled below from the DPreview studio test scene set to LOW LIGHT (very challenging compared with the DAYLIGHT illumination setting) for the Nikon D5500 below from ISO100 to 12800. Much of that chroma noise at the higher ISO should be able to be removed if dithering. Bear in mind the image shown is a tiny crop from the test image. Hopefully image is not degraded too much as a result of upload/JPEG

Best
JA
Attached Thumbnails
Click for full-size image (NIKON D5500 NOISE ISO 100-12800.jpg)
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Old 29-04-2018, 07:01 PM
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Thank you JA.

The 100 iso looks best to me.
I must work out a simple way to dither...

All of this is more concerning because I have been very happy running with 1600 iso which I never used once way back.
The irony is I am more or less happy with a pretty picture and tend to overlook the flaws but there is a side of me that seeks to do the best I can...I thank my mother..she always told me to do my best and that I did not have to win...but I win..only two wins in moto cross however but my excuse I was a late starter as in the age I took it up... but I did win all the other stuff art bird calls dancing arm wrestling pool☺ and judo stuff mmm in drinking I was impossible to beat as well.☺☺☺

Alex
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Old 29-04-2018, 07:24 PM
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Here's some comparison charts for the Nikon's.

http://dslr-astrophotography.com/iso...nikon-cameras/
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Old 29-04-2018, 08:50 PM
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Thank you Rick.
Alex
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Old 30-04-2018, 06:49 AM
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I might be a little late here Alex, but I never went over 400 ISO with The 5D, I found it to be the best overall.
If you have a perfectly black sky no light pollution to shorten the exposures, and your tracking was spot on I expect 100-200 would be great.

Leon
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Old 01-05-2018, 10:24 PM
Wavytone (Nick)
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Alex, all digital cameras seem to have a sweet spot with respect to ISO, as you know the fundamental issue is noise vs exposure duration. What I've done with mine is this:

- go to a really dark site where you really will hit the sensor limits regarding noise; suburbia isn't dark enough for this test.

- ideally have the camera on a tripod or mount so you can repeatedly photograph the same region of sky, this helps the subsequent comparisons.

- take a series of shots that should have the same exposure, using the same lens aperture for all (f/2 is good for this - helps if you can set the camera to manual everything) and varying both the ISO and exposure duration by factors of 2. For example:

ISO 100 for 4 minutes,
ISO 200 for 2 minutes
ISO 400 for 1 minute
ISO 800 for 30 sec
ISO 1600 for 15 sec
ISO 3200 for 8 sec

Even though star trails will appear in the longer shots, what you're really interested in is the sensor noise - which appears as a speckle with no trails. Anything that trails is a star.

Examine the dark areas of the resulting images and you may find the optimum shot (lowest noise) is not necessarily the base ISO of the camera. For example with both my Panasonic LX5 (base ISO 80) and GX85 (base ISO 200) the best results are at ISO 400.

From semiconductor theory it's possibly also temperature dependant to some extent. Although... I tried the test in subzero conditions one night at Shangri-La at 3200m altitude and still got the same results as I did at Mt Cook in NZ in summer (ie ISO 400).

Lastly some cameras do automatic dark frame subtraction in-camera (the Panasonics do) just to make matters more complicated.

Last edited by Wavytone; 01-05-2018 at 10:38 PM.
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Old 01-05-2018, 11:05 PM
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I have done extensive testing with my 1100D and 600D, and find that
results closely align with the results in the link provided by Alex.
My 1100D is clearly happy at 1600 followed by 3200.
My 600D is best at 800 followed by 1600.
In both cases the ISO below their respective sweetspots was inferior.
I also found that the noise situation definitely improved with wider
aperture. The difference between f/4 and f/2 was immediately apparent.
raymo
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Old 02-05-2018, 12:05 PM
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if you have phil Hart's shooting stars e-book he has a very good chart of a canon camera whereby he took a series of shots from iso100-3200 [maybe 6400 i forget] when he works the file in curves & strecthes them -they come out looking nearly identical. there were 1 or 2 iso's which look slightly better -iso i think is just a digital gain setting in a non-film based system
he also has a good noise explanation relating to filling buckets of water
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Old 02-05-2018, 08:24 PM
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Thanks to everyone I much appreciate hearing from people I trust.

I tried at 100 and 6400 and have yet to really examine them but initially the 6400 was a surprise as it looks rather good.
I think the omega at 400 seems noisey which I did not expect and it seems the Lobster was at 400 and I am doing a reprocess of it...and I have been stacking jpg so going to redo some in raw.
Back in Sydney after 10 hours on the road but its clear here but I found some black zambucca so might take a break for an hour or two and have a drink.
Great trip had some many ideas and made so many plans...
Alex
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Old 02-05-2018, 08:32 PM
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Raymo I will do as you suggest I think your approach will give me some direction.
Alex
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Old 10-05-2018, 09:03 AM
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Its a common question and impossible to accurately answer online, only as a generalisation. So many factors at work, including a Fact that no two [insert any camer make and model here] will ever have the same noise characteristics. Plus what you see as unacceptable noise amount, others may find acceptable. I'm yet to see a definitive SnR measurement test that can quantify to a value for everyone.

The real answer everyone must provide for themselves by testing the camera they own. Camera on tripod with manual settings and adjust only ISO, shutter time not important as you are looking to take shots of the noise, not really equivalent exposures (and you can find debates on more shots of less time vs less shots of longer time), all you can do is take noise shots to see what YOU feel is your camera sweet spot setting. do all the values at the same outting as quick as you can, leave camera on for 5min or so to let it warm up a bit (as it will when shooting subs) then take iso changing shots. I suggest use a burst mode to take several shots each time you click, so you can see how consistant the noise is at each iso.

You can also experiment with in camera noise reduction options too with this process just repeat the iso set again with different nr option, take notes as you make adjustments

if you shoot with a lens you should do a similar sort of test by adjusting the f-stop value along with shutter speed as you do want equivalent exposures this time since its signal not noise you're looking at. This will help you find the sweet spot of your lens for sharpness, pay attention to center frame and corners and how it changes.

After those two tests you have an ideal ISO value and f-stop value you can manually set, after those you only have shutter speed to ever worry about.
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