OzVMX Forum
Clubroom => Foto Forum => Topic started by: Ji Gantor on April 09, 2009, 09:20:35 am
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Photography is the science and art of catching light.
Light passes through our eyes into the retina and via the miracle of Gods work to our brains. There the light is decoded into many pieces of data that make up an image.
What we see!
What do we see?
Shapes, texture, colour, reflectivity, shades……..
Our brains are huge computers that can process vast amounts of information just from our eyes and enable us to see and recognise a ball, a computer, a friendly face……..
A camera is a device that allows us the chance to capture this light. The light passes through the lens and is focused onto a recording media. This media has taken many forms since the pinhole camera was built. To catch the light we must first ask ourselves “What is Light” and “Where does it come from”
There are many origins of light
The Sun,
Camera flash,
Fluro light,
Incandescent light,
Tungsten light…….
All of these light sources have different characteristics and have to be captured in a specific way so the subject will be recorded the way we desire.
I have never read a sentence yet that properly explains what light is. If I was asked what is light by a blind person my answer would leave them poorer for asking the question. Scientifically light is electromagnetic radiation, particularly radiation of a wave length that is visible to the human eye. Historically light from the sun chasses away the darkness of night. If we were to direct a beam of light onto a surface of a prism we would see many coloured light beams as it passes through. These colours from the light are what gives colour to every thing we see and the intensity of light is the variable that dictates the richness of colour. There are contaminates in between subject and recording media that can ruin and or enhance the images we seek. Take the sun in the morning or afternoon. The light at these times of day are amber and give everything our eyes see a golden glow. This is the best time to take landscape images but why is the light like this. The light from the sun in the early morning or late afternoon has to pass through a lot more of our atmosphere because of its low angle. Our atmosphere is full of dust and other particles that give the light this warm glow.
Ji
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JI, you got to stop taking those drugs or cut down on wikipedia sites.
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This is a typical sunset over my home town of Brisbane.
The golden glow is easily seen and when the sugar cane is being burned up north the sky is almost crimson.
What I have captured here is light.
The light from the sun that has changed colour because it has been tinted by atmospheric influences.
Ji
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The colours that are part of sun light can be seen through a prism but the most dramatic realisation is when you try and take photos under water.
Water absorbs light or should I say the colour that makes up light. This absorption is not even so it allows us to see the different colours of light the deeper we go.
The long wave lengths of light are absorbed faster than the short wave lengths.
At a depth of 30 feet all the long wave length colours such as red are gone. The further we go down the more colour is absorbed until all we are left with is blue.
I took the attached image at a depth of about 5 feet in Vanuatu in 1986. At this depth using just sun light there was some loss of red but you can see how the red is absorbed the deeper the water is.
Ji
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I took the attached image at a depth of about 100 feet in Vanuatu in 1986. At this depth using just sun light everything is blue but with the use of a flash, skin tone film and a red colour filter in front of the film the natural colours have returned.
This example is to show that all we are capturing is light.
Ji
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We have now seen that sun light can be changed via tinting or contamination and absorption. The next alteration to sun light is reflection. Most of us would have seen how blue the ocean can be in the middle of the day. This is a reflection of the sky. Another form of reflected light colour is in the snow fields or on a cloudy day. Again red is absorbed and we are left with blue. The brain is a mighty powerful thing and compensates for the loss of colour but our recording media does not.
I took the attached image on Mount Ruapahu North Island New Zealand in 2005. It was a clear day at noon and I used Fuji Sensia slide film. Sensia has a blue cast to it but I was after a cold and bleak feel for this image. The blue cast that the film has certainly made the image less warm but not to the same level as how it would have turned out had the photo not been taken in a snowy area.
Ji
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Photography is obviously your second great passion Ji.
Here's several of my shots which play with the light. In the first the ambient light was a lot less than what is apparent. I like each of them. The third impresses me because it very closely captures the late afternoon light of the time and the highlighted difference of the wave in and out of shadow is 'as live'. It will probably disappoint you to know all these shot were taken by a muggins with a little pocket size Olympus digital set on auto. That's me.
What I find the biggest advantage of digital you are not restrained by cost of film. Just take lots of shot and trash the crap.
(Each of them are a lot better at high resolution on my screen straight from the hard drive ;) :))
(http://i323.photobucket.com/albums/nn458/mx250syd/Picture064.jpg)(http://i323.photobucket.com/albums/nn458/mx250syd/PA130090.jpg)
(http://i323.photobucket.com/albums/nn458/mx250syd/Picture093.jpg)(http://i323.photobucket.com/albums/nn458/mx250syd/Picture133.jpg)
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Light can also be made into a colour we like or a colour we hate. A light source that we don't like in photography is the light from a florescent light tube, these emit a green cast and is not flattering to an image unless that is what the photographer was after. Modern digital cameras have a setting that can balance this cast out of the images. When film is developed this can be removed via a colour filter.
I took the attached image in 2006 in Brisbane at the River Fire festival. The fireworks are manufactured so when ignited they will burn a certain colour.
Ji
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Light has different wave lengths long and short so may be you are asking yourself "What is White Light"
White light or as close as we can get to it is 5500 kelvin and this is what most flashes are set to. If we buy light bulbs for our homes we should always get 5500K or white light bulbs. The light from these bulbs makes the home feel fresher and I can guaranty that you will notice a difference. 3000k is amber and 11000k is blue.
Armed with this knowledge we can select a colour cast for our photos and capture what we are after.
Ji
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Our eyes see colour and our brains enjoy gloss vivid clean colour like lollies or lip stick. A good splash of colour in our vista makes us feel great like the feeling you get when eating chocolate. This said, as photographers, our aim is to capture every colour that light posses green, blue, red, orange, purple and so on.
If the subject we are interested in is a mono tone or one colour we can add colour to the image by placing a colour filter over an axillary light source. This adds colour to our images in a subtle way that is hardly noticed by the viewer but is appreciated by the eye. The filter can be colour gel from a lighting shop or just cellophane from the newsagents.
See the green light I sprinkled over the rusty brown keys. This is a prime example of light capture and colour manipulation.
Ji
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How does light affect colour saturation?
Light plays a very important role when it comes to colour saturation. The best way to remember this relationship is "The more light the less colour the less light the more colour"
To test this go take a shot of a black dog while using a flash, when you review the image you will notice that the dog looks greyish.
To produce the most colour saturation we need the least amount of light. Not withstanding we still need an amount of light to show detail and to produce the correct exposure.
I took the attached image at dusk standing on the Good Will bridge on Australia Day 2007. This captured just about all the colours and the lack of light saturated them to perfection. I used Fuji Sensia that as we know has a blue cast.
Ji
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Ji, how about explaining shutter speed and what it will do to images of speed and aperture for depth of field and focal length. Maybe pushing film speed (ASA/ISO) so that the guys know about shooting in low light. Although over in Oz the sun is always shining so maybe something about polarizing filters.
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Ji,
Sorry but the reason the black dog looks gray has nothing to do with the amount of light, it is simply a result of the incident light meter that resides in all modern cameras [and the resultant exposure]. You can achieve a 'correct' exposure in any light level with the right technique and equipment. That doesn't mean that you can shoot, pin sharp, action images in the dead of night, that isn't practical but the theory still stands.
The incident light meter is designed to create an average exposure [of a ‘hypothetical’ average scene] and render this as a mid tone 18% gray.
If you aim your camera at a quality grey card and shoot you should get an accurate gray image. Aim your camera at a white wall and bingo you still get the gray wall - the camera assumes that it an ‘average’ scene and under exposes the image to produce an 18% gray. Shoot a black wall and you guessed it, yep another gray wall. As this time the camera has over exposed the image to change the gray wall [or dog] to an average 18% gray.
This is why any quality camera has an exposure compensation feature to allow the user to over-ride the incident light meter when shooting non-average scenes.
That is also why the well informed photographer will use a 'reflective' light meter, and/or their experience to over-ride the limitations of the incident meter.
Your golden premise that 'the more light the less colour… etc' simply isn't correct. Shoot an image at high noon, on a sunny day and you get great colour saturation, but you will also exceed the contrast range of the chip [or film]. Shoot on a cloudy day with diffused sunlight and you get a flat, low contrast image. Neither is wrong, but a well exposed low contrast image can be post-processed much more easily than an image with lots of deep underexposed shadow areas that contain minimal data or detail.
It is much easier to add contrast and a bit of midtone saturation [as all low/mid price digital chips lack mid tone saturation] to make a low contrast capture 'POP' than it is to try to add detail into underexposed shadow areas. That is why we use reflectors, fill in flash and multiple exposure HDR techniques in high contrast situations - to add detail [and therefore reduce the contrast] in the black or dense shadow areas. This is also the reason that we shoot in studios [where applicable], to control the quality, intensity and contrast of the light use in the shoot.
Another point to realise is that ALL low/mid price digital cameras use a chip with a ‘linear array’. The average quality mid price chip can record an image contrast range of approx 6 stops - at noon on a sunny day the contrast range can easily exceed 10 stops. So you have to make a decision which tones to clip. It all depends on the scene in front of the camera [this is where the operator comes in as the camera has no idea what it is looking at no matter how sophisiticated the incident meter algorithms are] as to whether you clip the highlights or shadows - but with no other intervention, 4 stops of data will have to be lost. So what does the linear array have to do with this?
As I said the average chip can record a scene with an approx 6 stop range. If your image contrast range is 6 stops or less then the chip can record the scene without clipping. If it is beyond this 6 stop range then you have to decide [by using the exposure compensation] which tones to clip.
A polar bear in a snow storm - you would probably clip the shadows [because they don't represent many tones in the scene]. A coal miner in the pit - then you would probably expose for the shadows and sacrifice the highlights. The term 'linear array' refers to the principle that in this 6 stop range, not all stops are created the equal. In an average chip with 4096 levels, the first stop of the chip [at the highlight end] will have 2048 levels and the next stop will have 1024 levels, all the way down to the last stop [the blacks or dense shadows] where it will only have 64 levels.
This is why it is vital to correctly expose the highlights with a digital camera. If you are one stop under exposed you have thrown away 2048 levels of tone, or half the data the chip is capable of capturing - that is why the exposure compensation feature is your best friend [or worst enemy if you choose not to use it].
Try to post-process an underexposed image and you will soon see the tell tale traces of ‘digital noise’ that exists in the shadow areas that have the lowest ability to capture variations in tonality.
How you use this information depends on what kind of photography you are doing. If you are happy to just point-and-shoot and just make a record of the moment, then do just that. If you wish to manipulate, or further process the image capture then you need to embrace these fundamental principals to ensure that you capture all the possible data to allow for effective post-processing.
If you are aiming to go down this path then I know you won’t have your camera set to process the images a jpeg file, but instead you will save them as RAW images. But that is for another time…
Also as I [am glad to] see that TonyT is back on OZVMX I look forward to his insights on this subject.
VMX42
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That's very interesting about the levels of tone in each stop of contrast. I never knew that. I guess it makes sense as it's much easier to pull detail out of a brighter scene than a darker scene. Exposures are always a bit of trial and error for me and I have to admit I've never played with the exposure compensation at all. Often in bright scenes I use fill-in flash to up the detail in the shadows. For example in this shot, I've used the flash to make up for the auto-rated exposure given the bright subject. I think it worked OK. In the second, one of my favourite photos, I haven't at all and just went with an exposure off the tree's shadowed area and ended up with a well over-exposed foreground. I don't mind that, but could I have done better with the knowledge re exposure compensation?
(http://www.ozvmx.com/images/forum/snow2.jpg)
(http://www.ozvmx.com/images/forum/snow1.jpg)
By the way, given I now have my new camera to play with and it saves to RAW format, can anyone offer up some more info about that? I can use either RAW PEF or DNG formats, and I am assuming DNG is more useful for most image programs as PEF is a Pentax format. I assume RAW contains all the image data and is therefore much easier to post process than JPEG (which I have read is a pretty lossy format). Any pointers about working with RAW and whether it's an advantage for a hack point and shooter like me?
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Graeme, VMX42 is the man to explain RAW v's JPEG and I want to here it all again to Jeff. Remember we talked about it, but being just an amatuer and when it comes to digital a complete novice so the more onfo I can get and understand the better.
I like the shoot Graeme, but then Im bais as I like snow ;D
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Yep, he knows what he's talking about alright. Complex subject especially when you add in the vagaries of working with digital. I have to say that I am with Ji too re the qualities of light. Late afternoon tones are always superb and so nice to work with, as are early morning. When it comes to bike mag photography, back in the day I loved ADB for their 'get in close' shots and the use of the fill-in flash to bring up the detail. The photos weren't quite as imaginative or technical proficient as some of the stuff you see today, but they really complemented the articles. I alo loved Motorcyclist's work around the late 70s - lots of pics taken early morning or late arvo with deep hues and lovely soft tones. They had a penchant for shots using natural backlighting at those times to really 'lift' a photo. Marvellous stuff!
Didn't mean to highjack your thread Ji. Back to you.
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Hey DJ,
Raw is pretty simple to understand. It is simply the unprocessed capture data from your cameras chip.
If you choose the save as a jpeg file then the camera will process the RAW image 'in-camera' based on the settings you specify [and some you don't] and using the preinstalled algorithms. All is fine if the settings, for example colour temp is correct, but if you make a mistake then it is difficult [and limited] as to the range of changes available to you before you start to seriously degrade the image. You also have to contend with the data loss of the jpeg compression and the conversion to an 8 bit file.
With a RAW capture, the file remembers all the camera settings but it doesn’t commit them to the file. When you open a RAW file in either your generic manufacturer supplied software or in Photoshop [or Lightroom] you have access to all the captured information and you are free to change or tweak the image characteristics as you see fit. When you are happy you can then process the image for printing. Additionally the RAW file will remain untouched, so you can go back and have another go if your not happy with the end result.
But probably the biggest advantage of a RAW file is that it is a 16-bit file.
An in-camera processed jpeg image is saved as an 8-bit file, which means there are 256 tonal levels between 100% colour and 0% colour in each of the 3 capture channels [RGB]. A 16-bit image has 65,536 tonal values between 100% and 0% for each channel. This vastly larger colour space allows significant and aggressive [if you choose] manipulation of the image before you start to degrade the resultant file. And if you use Photoshop Smart files or Lightroom then you have even greater control of the image before you reach significant degredation.
[As the next step HDR will then take you way beyond that, with muliple 32-bit images combined to allow an almost limitless contrast range. But you can’t take action photos in HDR].
The ways you can manipulate a RAW file before processing is truly astounding and continues to evolve at a great rate. Compared to in-camera processing it is another world.
DNG is a generic algorithm created by Adobe for the long-term storage and retrieval of bitmap files. Each manufacturer has their own version of a RAW file and you can’t [if you don’t have the software] open another makers RAW file on your computer. If as Graeme says he as the option of a Pentax PEF RAW format, he will have problems sending the file to DJ to process using his Canon RAW converter. Photoshop continually updates its list of RAW converters, but potentially older RAW file formats could be left behind and become unopenable [is that a word] in years to come. Kind of like having all your favourite MX footage on VHS tapes and only being able to access a DVD player.
So DNG has been created as an open platform format to try to ensure that you will be able to open your images in years to come. I don’t use the format so I can’t comment on the workflow, but I can’t imagine it would be a problem.
Like all things, it is good to be aware of the basics and make your own choices about how to incorporate this info into your photography. Don’t let the detail weigh you down and take the enjoyment out of it, but conversely if you know what you are doing: you can survey a scene, understand how the camera will see it, consider the histogram and get a picture in your mind as to how the capture will look before you press the shutter – then you will be able to really move forward with your photography. There is nothing worse than getting one great image and not knowing how to do it again.
But again it is horses for courses, I know many successful professional photographers who couldn’t care less about this stuff. They immerse themselves in the shoot and enjoy the spontaneous results – I am a bit of a control freak and I like to know and anticipate what results I am going to get. I think that explains why I will never be a highly paid fashion photographer.
VMX42
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I think that explains why I will never be a highly paid fashion photographer.
VMX42
And I just thought it was because you scare the girls, Jeff............... ;)
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Hey Tony,
I was going to say welcome back - but now I am not so sure?
I might scare the girls, but what kind of reaction do you think an old bloke in a vintage Merc towing a $7000.00 Postie Bike through Snow Town will get? I wouldn't stop and ask for directions if I was you!
Are you planning on having coloured tassels on the handlebars, or just 40 kilos of other peoples mail?
VMX42
P.S. are you coming to CD6. Come on… give the Merc its head over the Hay Plains and you only have another 12 hours to go…. It has to be worth it to catch up with those crazy Queenslanders doesn't it?
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what kind of reaction do you think an old bloke in a vintage Merc towing a $7000.00 Postie Bike through Snow Town will get? I wouldn't stop and ask for directions if I was you!
I reckon that makes the score one all.......... :D
Still waiting to hear back about a job over the CD6 weekend. I've given them a quote I can't imagine they'll accept, but you never know................ :-\
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love the outdoors,,,,,,,, :P ,,,,,,,, #'s one and six :o
http://news.ninemsn.com.au/glance/8097763/wildlife-photographer-of-the-year-2010
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I like the one with the stag but the dolphin one doesnt look real.