Noise!!!!!!!!!!!

[raymo]

Thankyou all; there's stacks of stuff there to keep me experimenting for months, and it will be months because we've moved into the time of year when suitable nights are about 1 in 10 if I'm lucky, [but that's another
story].
raymo

[lazjen (Chris)]

I'll add to the chorus of not using in camera noise reduction.

I build a library of darks for each ISO/duration combination. They're named with the temperature details, so they're easy to match with the lights (also have temperature details in the file name).

Liveview is off (it's power hungy and generates a huge amount of heat), focusing, etc is all done via the laptop (BackyardEOS mostly, sometimes APT). Images are stored on the laptop, not the camera.

I've got a power adapter for the DSLR that I run through my break out box (so it works for 240/12V) - this also means I'm not limited by battery time and can go all night.

I almost always use PHD dithering when taking images, so there's a very slight position difference - this improves the result in DSS (which, btw, you should be using the latest beta if you aren't already).

Flats/Dark Flats are taken each session (about 10 each). For the backyard I have a convenient house floodflight near by I can switch on that gives a nice glow to the white cloth over the scope. When I'm at a dark site, I either do the flats in the late afternoon or use the car lights.

[raymo]

Thank you all sooo much for the wealth of information. I have printed out
all 7 pages of this thread so I can peruse it at my leisure, and make some changes to my method of image acquisition.
raymo

[raymo]

Perhaps Justin or Chris could clarify what they mean by having Liveview
switched off while imaging[Justin said that it would get rid of the lines
on my images]. I only use it for maybe 20 secs or so with my Bahtinov
mask to get the focus right before starting the session. I will now be focusing using BYE. I don't understand why I would want Liveview on
during imaging.I like to store my images in the camera as well as on the laptop as a backup. This doesn't cause noise does it? Sorry, I'm not very
tech savvy.
raymo

[alistairsam]

hi Raymo,

you mentioned that not even one of your 60 sec subs was usable, are you able to post that here, or even a screenshot of it? would be good to see the noise you're referring to.

focusing with software is much easier.

You also mentioned you save as jpg's?

My suggestion would be to change the settings to save as raw and jpg, use the jpg's to browse and select the ones you want to discard, and then use DSS to stack the respective RAW's. you'll find that results will be better this way rather than stacking jpg's.

Cheers
Alistair

[pluto (Hugh)]

Originally Posted by raymo

Perhaps Justin or Chris could clarify what they mean by having Liveview
switched off while imaging[Justin said that it would get rid of the lines
on my images]. I only use it for maybe 20 secs or so with my Bahtinov
mask to get the focus right before starting the session. I will now be focusing using BYE. I don't understand why I would want Liveview on
during imaging.I like to store my images in the camera as well as on the laptop as a backup. This doesn't cause noise does it? Sorry, I'm not very
tech savvy.
raymo

There is no reason to leave Liveview running while imaging but some people might do it anyway and this would generate excess heat and battery drain, you're obviously not one of them so you don't need to worry

Writing images to the card would generate a bit of heat if you were taking shots quickly and it was constantly writing but writing an image every 30/60/90 seconds isn't going to do anything negative IMO.

In terms of heat, using Liveview on the camera and focusing using BYE would be the same, as the mirror is up and the camera is reading and processing image data, but I wouldn't worry too much as 20 seconds to focus is negligible compared to a night of imaging.

[raymo]

Hi again Alistair, thankyou for your continuing interest in my problems.
As I said the other day, I'm not at home at present, and don't have
access to my images which are on my laptop there. Even if I was there I wouldn't know how to send a screen shot. Another way of describing the
noise would be to imagine horizontal rows of seismic readouts of earthquakes, but with small spikes like little tremors would produce.
Another 1100D owner recently posted about the same pattern he was getting. The lines are really close together like knitting would be.
Research is a little difficult for me, as my laptop's memory is nearly full,
so I discard pretty much all of my substandard material. I just thought of another suitable description: barbed wire with the barbs almost touching each other. Even if I don't have any individual subs showing this effect, I will presumably have some finished images showing it. I usually minimise
it by saturating the black, but that loses me other detail of course.
raymo

[raymo]

Thanks very much Hugh, that cleared that up.
raymo

[nebulosity. (Jo)]

I have the whole screen turned off when I'm imaging with the 1100d, not just live view. I think it's the screen being lit that corses a lot of the warmth, not just the live view.

My sequence when imaging is this: turn on live view, focus, press live view button again to turn off live view and then press 'display' button to make the screen go completely black.

Imaging like this I get hardly any noise banding ( I think that's what they call what your talking about) previewing the image for a few second after its taken it doesn't corse any dramas.

Sorry if this is already what you do, but it seems to work for me.

Cheers
Jo

[alistairsam]

Originally Posted by raymo

Hi again Alistair, thankyou for your continuing interest in my problems.
As I said the other day, I'm not at home at present, and don't have
access to my images which are on my laptop there. Even if I was there I wouldn't know how to send a screen shot. Another way of describing the
noise would be to imagine horizontal rows of seismic readouts of earthquakes, but with small spikes like little tremors would produce.
Another 1100D owner recently posted about the same pattern he was getting. The lines are really close together like knitting would be.
Research is a little difficult for me, as my laptop's memory is nearly full,
so I discard pretty much all of my substandard material. I just thought of another suitable description: barbed wire with the barbs almost touching each other. Even if I don't have any individual subs showing this effect, I will presumably have some finished images showing it. I usually minimise
it by saturating the black, but that loses me other detail of course.
raymo

hi Raymo,

are the lines anything like this?
http://i96.photobucket.com/albums/l1...talBanding.jpg

is it vertical or horizontal?

There seem to be a number of reports of vertical and horizontal banding with the 1100d.
I've never seen it with my 1000d even with 10min exposures at 20deg C, sure lot of noise, but not bands.

I would've mentioned changing USB leads but you said you save it to the card...
when you do use USB to capture, make sure it is good quality and isn't running too close to your dew heater supply cable or other power leads.

See if you can capture BIAS frames. there's a long thread in SGL where they've got some good results with just using flats and BIAS, not even darks, to remove the banding.

make sure you save as raw+jpg when using BackyardEOS and change the image type to Light/dark/bias so the files will be tagged/named accordingly.

If your stars aren't elongated, you shouldn't be discarding frames.

Cheers
Alistair

[raymo]

Yes, that is what I do Jo and it certainly doesn't work for me. Up to now I have been imaging manually[which is a drag when getting a lot of subs],
so the screen only lights up after each shot for a fraction of a second
before I take the next sub. I am going to turn the screen off altogether
after focusing, and see if that helps, and also leave 10secs between subs
for sensor cool down. Oh well, keep trying.
raymo

[paul71 (Paul.)]

Hi raymo, I see you are still having problems with horizontal banding,
my 1100d is still giving me the same banding issues as you are having.
There are a lot of reports on the net relating to the 1100d and horizontal banding,when I had the problem last my sensor temp was in the high 30s,eg 38-39 and I was taking 5min subs.so maybe this was a big contributing factor.
I think when I am imaging again next all I can do is try a lower iso around 400 instead of 1600 and maybe shorter subs.
The thing that disappoints me most is that I bought the camera new and then sent it to the usa to hap griffin to have it fully modded, if i had known that the 1100ds were prone to this sort of banding i would not have wasted my time and money.
Cheers Paul.

[raymo]

Hi Paul, How do you know what the sensor temp is? I'm using lower ISO as my PA improves, allowing longer exposures, but have found that the noise at 1600 is hardly any less than 6400. Next step 400 and 800.
I don't frequent any other forums, so wasn't aware that this banding was
being discussed elsewhere; certainly none of the respondents to this thread have mentioned knowing of it. I wonder if it is confined to the 1100D. Assuming that this is an artefact of this model only, I certainly wouldn't have bought one either. Perhaps I was fortunate that I couldn't
afford to get it modded.Perhaps we could PM each other if we see anything of interest or importance about this problem crop up on the net.
Cheers raymo

[alistairsam]

hi Paul, Raymo,

I'd strongly suggest you'll acquire BIAS, Flats and Darks and then stack your images.
From reading forums, this seems to remove the banding and Justin here who has some very nice results from his 1100d from memory also uses flats, darks, bias. I wonder if he's noticed any banding.

I believe this has been noticed with 450d's, 300d's and 350d's, but not as much as the 1100d. I'm surprised as the 1100d is known to have low noise.

Cheers
Alistair

[raymo]

Hi Alistair, thanks for your contribution; I'll digest it along with all the other info I have printed out. I am still trying to find out how to know what the sensor temp is.
cheers raymo

[scagman (John)]

Hi Raymo,

The sensor temp, along with a heap of other data is recorded/embeded in the image. If you right click on 1 of your images, select "properties". This will open a window, click on details and should be able to find it in there. You can also use firefox with the Exif Veiwer addon to view it as well.

Hope this helps

Cheers

PS here's a link with some info on Exif files http://photographylife.com/what-is-exif-data

[raymo]

Thankyou so much John.
raymo

[raymo]

Been through 6 photos; no mention of the sensor amongst the scores of
items. The camera section has no info at all. I have looked at older images
taken with a different camera, and all the shooting details are there along
with the camera make and model, but still no mention of the sensor.
raymo

[rcheshire (Rowland)]

To be honest Ray, sensor temp is nice to know, but if you stick to the calibration formula and religiously take darks and flats immediately after or during imaging (bias if your software needs them), you shouldn't have a problem. Your image will be easier to analize for problems after proper calibration.

Temperature differences are inevitable with uncooled DSLRs. What matters is that you are taking calibration frames around the same ambient air temperature. If you take enough, the average is better and accounts for fluctuations in sensor temperature.

If you take your darks in an identical sequence to your lights the frames should be more consistent. It's all about consistency when working with temperature. That's why regulated cooling is an advantage.

Dithering, and I don't mean by a half or 3 pixels, but aggressively, for uncooled DSLRs, (12 - 15 pixels) will take care of a host of noise problems as well as inevitable calibration artifacts, due to slight temperature mismatches 5C or so.

An uncooled DSLR sensor is not at all like a cooled CCD.

Rant over...

[raymo]

Hi Rowland, I'm not tech savvy enough to be wanting to know the sensor
temp for practical purposes; I keep having people talking about it, so I was curious to know how to find out what sort of temps mine runs at.
The sensor temp doesn't seem to be where John said I should find it.
Searching through my images I find that some images have the imaging
details[camera make/model, shutter speed, etc : and others have a blank
section where the camera info should be. Mysterious. This digital business
is like a twisting road, you've no idea what's coming next.[except clouds].My next adventure is to get my BYE in use. I believe I can dither with that, but need a plug in.
raymo