[Steve]

I took a couple of hours out the other night to do some night time photography of a local landmark to see if I could capture something suitable for entry into this months competition of Architecture/buildings. Even though I am not allowed to enter I still like to capture something that fits the theme to "join in" with you guys and keep myself interested. I have an advantage of being able to show you my attemps during the run up to the competition though The Lowery at Salford Quays is a weird building but strangely beautiful. The shot below was captured on my Canon 20D using the Canon 17-40L lens.

Manual control, F22 for 30secs, remote release. Final image run through Noiseware then colour balanced using curves in Photoshop CS to remove the orange noise pollution from the city lights. These versions could have done with a lttle sharpening added for web display but the large version (whichI did the work on) is fine. you'll have to take my word for that 8)





A larger version (1100x492 and 179kb) can be viewed by clicking the link here

[Matt]

Last time I show you a vantage point












Nicely fixed Steve, it looks a lot better without the red sky doesn't it?
I would have liked to have been there with a nice twilight sky.

[lolyton]

Brilliant effort!

I was in a hotel up there the other week (golden tulip it probably just about visible in this shot), wish i had my camera with me. But travel methods meant i could not. I like a bit of night photography every now and then. I feel it brings out the best in places and from my experience of this place Steve's image certainly has brought out the best.

Spot on!

[CT]

Very nice shot. There's not much wrong with digital when you can achieve night images that noise free.

[lolyton]

How do you digital guys go for 'reciprocity' do you still get it and need to compensate on exposures? Though i guess this isn't sooo much of a problem as you can see the pic straight after to see if exposure is alright or not.

[CT]

That's interesting actually. Reciprocity failure used to be a consideration with shutter speeds quicker than 1/1000 sec and longer than 1 sec. With modern SLRs commonly having top shutter speeds of 1/8000 sec, I'd guess things have been improved somewhat as far as filmstock is concerned. I suppose there's no reason really why compensation for reciprocity failure couldn't be programmed into the processor with a digital camera, but I doubt it is somehow. As you say though, the advantage of a digital camera is you can 'suck it and see' and keep previewing your images till you're happy with the results.

[Steve]

If By reciprocity you mean..the relationship between different choices of aperture and shutter speed that result in identical exposure.

For example..In most situations there is an relationship between aperture and shutter speed, with a wider aperture requiring a faster shutter speed for the same exposure. For an exposure value of 10 may be achieved with an aperture of f/2.8 and a shutter speed of 1/125 s. The same exposure can also be achieved by doubling the aperture to f/2 and halving the shutter speed to f/250 s; or by halving the aperture to f/4.0 and doubling the shutter speed to 1/60 s.

However, during very long exposures, sensors can respond much more slowly than usual, resulting in underexposure. It is said then, that reciprocity failure has occurred, i.e. the conventional relationship between aperture and shutter speed has broken down. Most film manufacturers publish data on the latitude of their films (how much they can be pushed or pulled beyond their normal exposure range), and also reciprocity corrections. For example, if a light meter indicates a required EV of 5 and the photographer sets the aperture to f/11, then ordinarily a 4 second exposure would be required; a reciprocity correction factor of 1.5 means that the actual exposure must be extended to 6 seconds.

With digital it’s a little different and the best way is to check your results as you shoot using the histogram.
For this shot is was unnecessary as It was just inside the limits of the camera light readings and I also shot this in RAW which gave me extra headroom to recover the picture if required (this was not required in the end as the exposure was spot on though.

However if it had been outside the range when I was shooting I would have done as below…btw this is one of the tips and tricks that can be read in article that I wrote a while ago and is posted on the front of the site here

The Easiest way I know is to set the camera on manual and the aperture wide open (small F stop), then check to see what the meter says. If necessary increase the ISO up too, until you get an exposure of less than 30 seconds. Then start adjusting back to the aperture and ISO you really want, doubling the time for every full stop. Here is an example for clarity..

If you have to set the aperture to f/4 and ISO 400 to get a reading under 30 seconds - for simplicity, say that the camera picks exactly 30 seconds but you really want f/11 for good depth of field, and of course you want ISO 100 to keep noise to a minimum.

f/4 to f/11 is 3 stops (f/5.6, f/8, f/11). So you have to double 30 seconds 3 times (1 minute, 2 minutes, 4 minutes)
ISO 400 to 100 is 2 stops (200, 100). So double 2 more times (8 minutes, 16 minutes).

In this example you would set the camera to f/11, ISO 100 and an exposure of 16 minutes.

Since 16 minutes is a long time to wait I'd cut that in half by underexposing 1 full stop and do a picture at 8 minutes and then check the histogram. Judging the histogram will give you an idea for the next try. Sure, the 8-minute shot might be an extra, unnecessary step, but why wait 16 minutes to find out it's messed up? Also remember that most photographs can easily be recovered from being underexposed by 1 stop in most image editing software packages, so if time is a premium, sometimes this can be a life saver.

[lolyton]

Sorry i was being lazy, i should have said reciprocity 'failure' but forgot to type the failure bit.

However, during very long exposures, sensors can respond much more slowly than usual, resulting in underexposure. It is said then, that reciprocity failure has occurred, i.e. the conventional relationship between aperture and shutter speed has broken down. Most film manufacturers publish data on the latitude of their films (how much they can be pushed or pulled beyond their normal exposure range), and also reciprocity corrections. For example, if a light meter indicates a required EV of 5 and the photographer sets the aperture to f/11, then ordinarily a 4 second exposure would be required; a reciprocity correction factor of 1.5 means that the actual exposure must be extended to 6 seconds.

This was exactly what i was referring to. And as usual explained perfectly!

As a rule, do you reckon you get about 30 seconds of open shutter before reciprocity failure starts to effect the exposure?....shooting RAW!

[Steve]

Originally Posted by lolyton

Sorry i was being lazy, i should have said reciprocity 'failure' but forgot to type the failure bit.

As a rule, do you reckon you get about 30 seconds of open shutter before reciprocity failure starts to effect the exposure?....shooting RAW!

No problem that’s what I thought you meant and as its quite a advanced topic I took the opportunity to expand on the answer to aid others that may have been interested.

To answer you last question, I really don't know The longest time exposure I have done was about a minute and that was shot in RAW mode. The results where pretty much spot on out of the camera though and only needed a small amount of adjustment that was well within the range. Modern digital photos respond well to exposure adjustments and just one stop reduction can half the time the shutter needed to be open so there is a large margin for error and reciprocity failure is all but a thing of the past.

[lolyton]

reciprocity failure is all but a thing of the past.

All sounds good to me!

[Matty]

no idea what your talking about, but its a nice picture!

[Steve]

Originally Posted by EosD

no idea what your talking about, but its a nice picture!

:lol: [smilie=l: [smilie=w:

[Arkady]

Reciprocity Failure is when the metered exposure fails to deliver the expected result because of the film not behaving according to the rule of 'reciprocity'. It is different for every type of film and tables are available from the manufacturers to tell you how much extra exposure to apply in various conditions, typically slower than 1 second and faster than 1/100,000 sec. Most of us only experienced this with slow shutter speeds as we didn't have access to ultra-high shutter speeds in the Good ol' Days.
With digital there is a different problem, that of increased digital noise with long exposures. This is (roughly speaking) caused by the pixels recording too much information at each pixel site and rendering a false colour value as a result, which manifests itself as 'noise'. Modern Pro cameras have more sophisticated software to take account of this: some manufacturers even render a 'black' pixel for each colour value and combine this during interpolation to lessen 'noise' on long exposures - the reasoning being that black looks better than red, green or blue against a dark background.
When we tested the D1X in 2002, we recorded images at up to 32 seconds with no significant noise at 125ISO, which gave better results than rating the chip at a higher speed, say 800ISO.
Since the firmware update two years ago, it's even better and cameras bought in the last year should be even better.
Cheaper cameras - less than £800, say - may be less suited to long exposures - do a test before you buy, if in doubt..