Exercise : Scene Dynamic Range

SCENES WITH DYNAMIC RANGE

The scenes below offer a range of DR.  The dark silhouette of the trees against the orange sunset.
Secondly a garden shot, the dark treees and bright sky, as with the third of the horses in the field, the dark colour of the pony and light sky.
The bright sunlight highlights the statue just causing fractional clippings / highlights and to the darkness of his jacket.
The final shot is one with a low range - neither highlights or lowlights, quite a flat image.

HIGH 

FLAT/ LOW

Exercise : Your Cameras Dynamic Range

Your Cameras Dynamic Range


Both highlight clipping and and noise are digital problems, they are at opposite ends of the tonal scale.  They define what is known as the dynamic range of the camera.  The easiest ways of measuring it is in the form of f-stops.

The dynamic range is the number of stops between the brightest highlight and the darkest shadows.  The cameras range is less than that of a scene - something has to be lost.  This is the cause of most of your exposure problems.  Highlight clippings are one end of the scale and are therefore easier to find, and noise determines the other - this is not always as easy to find.  There is a point at which it is impossible to distinguish between noise and real detail.  To find this you need to lighten the image in photoshop temporarily to see.


Ths scene below is of high dynamic range.
Bright sunlight.
At least one reflective surface.
An area of deep shadow with a dark surface.
A3 white card as highlight.

The ISO is set to low and set the exposure to the white card with no clipping.

The white card here measures 50cm x 70cm  ( Img 6902 )  1/1000   f8

I've opened the image in photoshop and checked the RGB values, they were all to 255.  
Then I moved to shadows and adjusted the brightness until the details were visible.  This was
+3.60 exposure.

I would say my Dynamic Range was about 8 or 9, however I have printed details from the internet which all vary and say 10 or more.

Items researched on Internet.

Exercise : Your tolerance for noise

YOUR TOLERANCE FOR NOISE

This is my second attempt at 'Tolerance for noise' - hopefully now I understand, well actually I do understand the effect of noise its just that I didn't do the exercise correctly, and Im sure when I came back to typing this up I would have realised that it was incorrect.

When I looked in Lightroom, I noticed that when studying a part of the floor its starts off the floor becoming darker but still having all the detail, but then once we get to 800 and 1600 the same part of the floor may have look a little lighter but its sort of smudgy - noise.

Its is hard to differentiate between shadows and noise sometimes, and the noise can be lost as shadow.

IMG 7140

ISO 100   1/8   f3.5

IMG 7142

ISO 200  1/10   f3.5 

IMG 7143

ISO 400    1/25    f3.5 

IMG 7144

ISO 800    1/40     f 3.5

IMG  7145 

ISO  1600       1/80     f 3.5

______________________________________________________________________

Well this exercise has gone completely wrong - my tutor has pointed out that my shots should be getting darker as I change the ISO not lighter as they are here.

I think - hopefully - I may have realised this once I typed my notes up - as I did know this was the aim but it looks like the exercise just went wrong when I was taking the shots.  Im not sure exactly what has happened.  It was maybe as suggested that I kept my camera on whilst making changes to ISO and progressively over exposing the image. So the images below are now VOID .... and hopefully I have learned from my mistakes.... which I feel I have.

IMG 6823

ISO 100  1.6  80

IMG  6824

ISO 200 

IMG 6825

ISO 400

IMG 6826

ISO 800

IMG 6827

ISO 1600

Exercise : Highlight clipping

Highlight Clipping


The exercise is to find an scene with a range of brightness.  I have taken an image as a sample, in auto,
Then I have found the setting that shows Highlights and made a note of the shutter speed and aperture.
I have increased the shutter speed by one stop by adjusting the shutter speed. As you make this increase  the highlights increase also.

Then I have taken three more shots with a decreased shutter speed, exposure, so these five frames have all been separated by one fstop.

I have opened them in Lightroom to compare side by side.  Then I looked at them magnified.  I selected a area of the curtains first and the things I noticed were that some of the colour remained but very bright, nearly loss of information, the colour weak.  I noticed the biggest colour loss is in the window, the sky outside.  This is the brightest point and biggest detail loss.  Also in one of the pictures the edge of the orchid is lost against the sky and as far as I could see there wasn't anything I could do in Lightroom to recover this.



And I feel the best image is this one below....... There is slight colour loss in the sky though the window, but there is still detail of the orchid against the sky.  The colour has kept in the curtains, although lightened.  The rest of the room could maybe be lifted slightly in exposure but this would be adverse to the highlights making them lighter also.

IMG 6834

______________________________________________________________________




This image was a sample image taken on auto ..

IMG 6831

1/100  5.6   ISO 400

IMG 6832

1/100   3.5  ISO 200

IMG 6833

1/125  3.5  ISO 200

ONE F STOP BRIGHTER..  ( shutter speed ) ....

IMG 6834

1/50   4   ISO 200

THREE SHOTS, 1 F STOP DARKER (Shutter speed ) .....


IMG 6835

1/100   4   ISO 200

IMG 6836

1/250   4   ISO 200

IMG 6837

1/500  4  ISO 200

Exercise : Sensor Linear Capure

This is the first exercise of part two.... Sensor Linear Capture 


The instruction is to take any Jpeg image, I selected one taken in a recent trip to Paris.  I opened this in Photoshop and converted it to 16 bits per channel.  Image - Mode - 16 bits.

Here I have gone to image - adjustments - curves and made a curve using a few points to make it smooth.  It has made the image dark.  This is what the image would have looked like when captured, before the cameras processor has got to work.  I saved this image (Paris16bt).

I reopened the first image and put along side this one, looking from  one to the other.  I opened the histogram for both.  The dark image the histogram was pushed to the left, confirming the darkness.  The histogram for the original image was more central showing an even coverage.  I have made a note of these histograms in my notes.  What this means is that most of the levels available to represent the tones are devoted to the brightest part of the image, while the darkest parts - the shadows at the far left are actually represented by very few levels.  This also has a very important implication for noise.

I have reopened the dark image and opened the curves dialogue.  I created a curve and tried make the image look as close to the original as possible by adjusting the curve.  I did feel maybe I couldn't get it exactly, but this may be lack of photoshop knowledge.  I have the new image below (Paris16bt 2).

This has done more or less what the cameras processor does each time.  Notice the biggest effect has been on the darkest parts.  They have been lightened by what seems several stops.

If there is noise in an image it is concentrated in the shadows.  As captured, before processing in the camera, it is in a sense buried in the overall darkness.

However the strange curve that has been applied to lighten the image to a normal appearance has the unfortunate side effect of exaggerating this noise because it lightens the shadow areas so strongly.

Response to Tutor Report - Ass 1

I received my tutor report for this first assignment. thank you.  I have read through and taken note of what was said.

In response I will keep contact sheets from now on, I did in previous projects, keep rough copies of all my photos which I have in my folders.  I shall now print off all I have for this first part of this assignment and carry on as I continue, keeping a record of my shots.  I shall learn to do this properly and make it part of my routine.

In the last two sections that I have completed the tutors have only wanted the final 12 shots to be handed in, but I can put all into the Dropbox for your reference, and I would be grateful for your comments on my selection choices.

I think with the picture 6618 - I chose this more because I liked the picture and wasn't really thinking whether it fitted in with the rest of the selection.  This I obviously need to concentrate on more.

Thank You for the 'image numbering' link, this I have printed off and read, and taken note.  I shall now start my own file naming and see how it works for me, it may take a few adjustments.  I hope to find a system that suits me as I can see the importance of good numbering, especially in the work environment, when you need to identify who has been working on a project or photo.

As suggested I shall purchase a decent light meter, which I am looking into now.

I have been reading various reading material and looking at other works.  I have books on photoshop learning and also camera magazines.  I will make sure that from now on I log all that I am doing on my Blog.

I have also purchased the two books that you recommended - Digital Asset Management for photographers and Colour Management for photographers. Which I should get from Amazon tomorrow.

Short List of Photos for Assignment One

Here are a selection of photos of the Chelsea Flowers Show, it is a short list before I make my final choices.


Marble Body - IMG 6512

Camera - IMG 6518

Orange Chairs - IMG 6519

Green Garden  -  IMG 6555

Waterfall  -  IMG 6582

Cameraman  -  IMG 6595

Alys   -   IMG 6615

Fern  -  IMG 6618

Chelsea Pensioners  - IMG 6632

Purple pair  -  IMG 6641

Orange Brolly - IMG 6505

Mauve Bronze  -  IMG 6643

Parasol  -  IMG 6646

Jubilee  -  IMG 6676

Tulips  -  IMG  6663