Alley in Pisa, Italy

by Lars Kotthoff

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I have a Canon 550D using a 10-20mm Sigma lens, with tripod.

I have taken some photos of my city at night, and while the shots are ok... upon zooming in just a little you can see many lights are blurred and just not very sharp.

I set up two different ways, with ISO 100-200, F16, Shutter '25 or more... or i shot ISO 100-200 F6 with a shutter of about 6-8 seconds...

I used self timer and there was no wind, and I was on on stable ground...

I used auto focus on something in the middle frame... and this lens has no stabilizer, so that didn't come into it.

The effects I get are ok — he water in the river is very glass-like, which I love, and the colors are ok... but it's just a touch dark maybe — and just not *sharp.

What am I doing wrong?

The only thing I can think of is mirror lock... and maybe focusing with live view...

enter image description here

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2  
You can use hosting like imgur.com to post your photo ;) –  zacharmarz Jun 6 '12 at 6:31
    
i did that...thanks please take a look and see if you have any advice...thanks alot i.imgur.com/a8N5N.jpg –  Kelvin Jun 6 '12 at 8:33
    
I see a lot of JPG compression artifacts, but apart from that it looks fine. Is this the image straight from your camera or has it been post-processed? If this is straight from the camera I'd be concerned about those artifacts... –  Andrew Heath Jun 6 '12 at 8:55
    
its just straight from the cam i didnt adjust anything...i shot on the 2nd large L which is two down from L+RAW...im not sure what you mean about JPG compression artifacts? i guess you mean its changing my pic in compression and i should go straight to RAW? –  Kelvin Jun 6 '12 at 9:02
1  
Hi Kelvin, if you look at the Quay West building in your image, towards the top left there are 4 images in a square arrangement that are particularly bright. When viewed at full size you can see all sorts of image irregularities in the spaces between the windows. While a certain amount of "noise" is to be expected, what I'm seeing there looks a lot more like poor quality JPEG compression. Unless you have serious space concerns, you should be shooting on the best JPEG quality setting your camera has. See page 72 of your camera's manual. Choose the highest "L". –  Andrew Heath Jun 6 '12 at 9:15

3 Answers 3

up vote 5 down vote accepted

One possible explanation is that you're seeing the effects of diffraction softening your image at f/16 but since you also tried at f/6 and still got soft results it must be something else.

Mirror lockup won't affect a 25 or even 6 second exposure - the vibration die down quickly thus the percentage of the exposure during which the camera is vibrating is small enough not to affect the result. It could be simply that your images are slightly out of focus due to slight miscalibration of either lens or camera. This can be worked around by focusing with live view at 100% magnification (as you suggest).

edit:

After looking at the image, I don't know the 550D or Sigma 10-20 very well but that doesn't look too far off what I would expect for an ultra wide on an APS-C body. It's not tack sharp but with night photos you get a lot of flare and haloing as you're shooting into the lightsource(s). There's also a lot of JPEG compression artifacts either from imgur or you camera which does help. And possibly a little diffraction and/or lens blur if the focus wasn't spot on.

The bottom line is, I don't think there's anything wrong with the image - you've just fallen into the trap of viewing images at 100%. I think what you've captured there will look great in print.


The biggest piece of advice I can give about night photography is don't do it at night! You;re just making things much harder.

The best time to shoot is during twilight, where artificial lightsources show up, but when you still have enough daylight boosting the darker parts of the scene, taming the dynamic range. The best part is shots under these conditions still look as if they were taken at night!

See this example, straight out of camera, no HDR going on:

And here's an enlargement (not 100%):

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ok i uploaded a pic, please have a look i.imgur.com/a8N5N.jpg –  Kelvin Jun 6 '12 at 8:32
    
Matt, thanks very much for the info, im only new to photography i dont know anyone else who does it, and so i guess im judging what i do against things i see online and in mags so its great to get some info back from people who know more than me...its good to know im on the right track and not screwing up totally :) its a great hobby thats for sure :) all the best –  Kelvin Jun 6 '12 at 11:37
    
@Matt Grum - and [then you can do this to it :-) ](i.stack.imgur.com/wcxzI.jpg) - just playing / very rough, but has potential :-) –  Russell McMahon Jun 7 '12 at 3:17
    
@matt, beautiful pic :) wonderful place. –  Kelvin Jun 7 '12 at 11:20

I think that you can be pleased with the overall result given the equipment that you are using. You are fighting against effects which are unbeatable without cheating and compromise. If you want substantially better you need better equipment or you need to "cheat" or both.

There are several apparent affects at work here.

As Matt says, there are substantial JPG compression artefacts. The original file from imgur was 750 kB suggesting it had been compressed substantially somewhere along the line.But, this is probably not a major contributor.

Consider the marked up version below.
You can also look at the marked up imgur version here and
As marked up version here - click icon 2nd from right above photo to "download original file".

enter image description here

  • The target is just too big for the available pixels!!! - it's a magnificent view but

The 550D in full song produces a maximum 5184 x 3456 = 18 mp image and the imgur copy was 3888 x 2592 = 10mp so it's about 45% of the resolution of the original area wise or about 75% linearly. Even given another 33% you just haven't got enough pixels for the details. Here's an example where the bloated D800 sensor almost makes sense.

Camera needs to be set to produce max-everything. RAW if using RAW. Best possible jpg if not. EXIF or at least core data for this particular image would be useful.

See note G on image - the streetlight has been blown up to show the detail. That's a 30 x 30 pixel original as it came to me. There is not enough detail there for the light to be expected to be much sharper than it is.

  • You may be getting visible diffraction effects. The tasteful starring on the street lights is often a sign of small aperture and possibly diffraction. You say f16 which seems probably about marginal for such effects.

  • The sensor is saturated in luminance (highlights "blown") and so also in some or all 3 colour channels in many areas.

You cannot expect "genuine focusing" of original material if the highlights are fully saturated and detail is destroyed.

This is an unavoidable result if you want to render a picture with such wide dynamic range and achieve an eye pleasing result without resorting to HDR, tone mapping or magic in general. Notes A. B. C, E show histograms of small areas.

The light at A has a nicely blown spot of 100% white ijn place of the light. The brain accepts that without much complaint.

The light at B also has it's max level fully saturated - red channel shown here - but has a very large component of output across the range. (What the histogram shows depends on how much surrounding dark gets included - but it's clear that "tone mapping" or HDR or in camera local contrast management (DLighting etc) would render this better if violently enough applied.

I included C to show that a line of lights with surrounding moderately lit areas has much full saturation even though this is not necessarily obvious at a glance.

Where's Wally / D ? ?

E is on the river reflections - the brightest spots are saturated.

I looked at F to see if some sort of filtering might help the lights. Blue is well down but red and green are well saturated in the centre.

Overall it's a nice image.
It would arguably tolerate a somewhat reduction in total exposure and this will help some of the more blown highlights - but only somewhat.

This is an example what HDR is made for (an opinion, feel free to disagree :-) )- tastefully used, possibly with manual control, it will probably add much - but the effort may be severe and many will not notice.

Selective contrast or brightness control would also probably help - depending on how the camera was set, more aggressive treatment may be available.

Playing with aperture will confirm or reject the thought that you are getting some perceptible diffraction effects on point lights.

In the days of film, some serious dodging and burning might be invited.

How good is your tripod?
Have you trialed the tripod / camera / timer setup on known perfect point sources with perfect focusing and time delays of the same magnitude? In recent tests at extreme settings and using a focus magnifier I was somewhat surprised at how un-solid and apparently solid tripod mount was and how long it took to settle down after last being touched or knocked . That was extreme (1275mm equivalent focal length - the orbital motion of the Moon at the fl means it takes about 20 seconds for its edge to transit the frame!) but still applicable to your situation and the focus magnifier gives you insight into vibration that the standard viewfinder will never give you.

I haven't mentioned lens quality as it's something of an unknowable and there is enough above to explain what you are seeing (or are not seeing) that really needs addressing before a lens improvement will help vastly. I think! Lens experts by all means disagree.

I haven't mentioned atmospherics, which are also a variable feast and not easily knowable. Evening when cool and calm (or cooler and calmer) is generally a good time in that respect.

Image duplicated to minimise scrolling. Remove if desired.

enter image description here

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1  
Nice analysis, Russell! –  Andrew Heath Jun 6 '12 at 12:19
    
+1 I see I have a lot to learn :) –  zacharmarz Jun 6 '12 at 12:58
    
+1 for "...would render this better if violently enough applied..." GREAT ANALYSIS. I think I learned a few things here! –  huzzah Jun 6 '12 at 15:15
    
i now feel totally retarded haha..but i still thank you for the info, i have no idea how you got such history from various part of the photo like that but its great information. Ill be going back to the location in a few days to try again after all these tips and see how i go..the best thing as a beginner is hearing ''Overall it's a nice image.'' from an experienced photographer. Thanks for taking the time in making such a detailed examination of my photo :) i have heaps to learn. –  Kelvin Jun 7 '12 at 9:05
    
@Kelvin - I used a very blunt tool to get information from selected areas - some software will do it far more easily. Most viewers will give a histogram of the whole image, often with luminance and RGB displays. In this case I highlighted each area and then cut and pasted it to a second copy of the viewer and then displayed a histogram of the "whole image" which was now the selected part from the larger image. Where useful I then copied the histogram and pasted it back. ie a manual process. Doesn't take long and can be useful. Better is a viewer which allows histograms of selected areas. –  Russell McMahon Jun 7 '12 at 10:28

I weight down my tripod by hanging my backpack on it when shooting long exposures to stop any extra movement. I find this greatly helps keep the shots sharp and minimize the blur I used to see.

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Weighted tripod is a good idea. Effectively adds to rigidity of the system. –  Russell McMahon Jun 7 '12 at 2:55

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