Exposure Compensation

mata.morrison

mata.morrison

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Matthew
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Hi all, as some of you might know I do a lot of night photography. I have been doing long exposures for a while now, last week I was doing so star shots. To do this I know the basics are high ISO, as big an aperture you can get and as as possible shutter without creating trails.

So my shots were about 1 minute with my 10-20mm Sigma at the 10mm, F4 as wide as it will go and iso 1600 as high without being un-useable. This gave slight hints of trails and a decent outcome. I could go shorter and then boost the exposure in LR, however if I boosted the exposure comp to +2/3 what will this give me, where does it get its slight boost from? Will it affect the exposure time any or ISO as I know it can't adjust aperture, or does it just do it in camera? Or will it do nothing for helping me get a bit more light without affecting the trail effect?

I know I could just go out and try it but weather is stopping me so far and its just a thought thats come to me just now.
 
ex comp will change the shutter speed ,,plus comp ,longer shutter speed ( longer trails )
 
Use manual settings it is a lot less confusing

you are left with
- ISO
- Aperture
- Shutter speed

Getting trails or not - is a function of time. under 25 seconds = no trails

that leaves you with ISO and Aperture to play with
 
Exactly what I thought, so it won't really help me get more light without making longer trails. Thanks guys.... Should really save up stack of monies to get some faster glass... Maybe I should have gone for the 3.5 afterall haha.
 
Richard King said:
Getting trails or not - is a function of time. under 25 seconds = no trails
Click to expand...

With the 10mm the OP is using yes but otherwise it is dependent on focal length, longer focal lengths will exhibit star trails at shorter shutter speeds than wide angles.

For the record the 600 rule will let you know how long you can go before star trails, divide 600 by the focal length (in 35mm terms) of the lens you are using to give the maximum exposure time.
 
Personally, I wouldn't use high ISO or fast glass for star trails.

You need to keep the shutter open for a while to get long enough exposure to capture movement so I would be inclined to go for f8 and ISO200/400 and leave the shutter open for several minutes.
 
Russ77 said:
Personally, I wouldn't use high ISO or fast glass for star trails.

You need to keep the shutter open for a while to get long enough exposure to capture movement so I would be inclined to go for f8 and ISO200/400 and leave the shutter open for several minutes.
Click to expand...

The difficulty there is the amount of noise pollution in most parts of the UK.

Using wider apertures emphasises the trails, then stacking them minimises the noise pollution issue. It also reduces long exposure noise, hot pixels etc.
 
Russ77 said:
Personally, I wouldn't use high ISO or fast glass for star trails.

You need to keep the shutter open for a while to get long enough exposure to capture movement so I would be inclined to go for f8 and ISO200/400 and leave the shutter open for several minutes.
Click to expand...

Fast glass can help focussing, which i find bloomin' difficult when doing star trails!

And don't forget the stacking method, has saved shots a couple oftimes when the lens had dew settle on the lens after half hour or so. Since i had 60 shots with no dew, at least i had something workable...
 
Thanks again guys, just to reiterate... I don't want trails ;) I can do that easily enough. I was just trying to find out if adding exposure comp would give me more light. I have 37 seconds given the info by mark, f4 and iso 1600 being my best bet for no trails.

My question of exposure comp has being answered in that adding it adds to the exposure time... Which will then add slightly more trails. So will just stick with what I have.

Cheers
 
markmullen said:
The difficulty there is the amount of noise pollution in most parts of the UK.

Using wider apertures emphasises the trails, then stacking them minimises the noise pollution issue. It also reduces long exposure noise, hot pixels etc.
Click to expand...

A quick look at where he lives and you will see there aint much light pollution up there haha. In fact im dying to get back there to see my family and get the telescope out and tracking again.
 
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