Gabi Butcher
07-11-2008, 08:43 AM
Now that everyone knows where to find the EXIF of your digital pictures we can move to the next level and begin to learn what all that information means and start taking charge of ... yes... the camera will no longer be the boss of you... it will be a slow process but I'm sure it's going to be FUN and enlightening.
Today we will learn about ISO, on further exercises we will return to this because as you will find out EVERYTHING on a camera is related... If you change one thing it affects all the others, but don't worry with practice this will all make sense in a while.
ISO sensitivity expresses the speed of photographic negative materials (formerly expressed as ASA).
Since digital cameras do not use film but use image sensors instead, the ISO equivalent is usually given.
What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.
And, where you would have needed to physically change to a different roll of film if you wanted a different ISO speed, digital technology allows you to simply dial one in. In this way, you can record images taken at different ISO speeds on the same memory card.
There is a lot more to this but with this information we can all start to change some things...
What are we going to do?
1) Place an object on some place with light (natural if possible) and take a photo of it in the AUTOMATIC mode.
2) Now with the same object and light I want you all to take your cameras and put it in the MANUAL mode (if you don't know where it is let me know and we can figure it out together - BTW ALL cameras have some sort of manual mode even the point and shoot ones). Try to find where the ISO option is (mine is in Manual/ISO) and put it in 100 - take a picture
3) With the same scene change now the ISO to the highest your camera allows (mine is 400) take the same shot...
4) I want all 3 images WITH the EXIF information posted in your post, PLEASE try to make the visible so everybody can see the different modes the camera used.
You will note that the EXPOSURE TIME from the ISO100 is very different than the other with the higher ISO and that the image with ISO100 does not have as much GRAIN/NOISE as the one with the higher ISO.
Next exercise we will learn more about Exposure Time
If you are using a point and shoot you will probably NOT SEE any changes... WHY? Because you don't have the full control of the point and shoot's BUT when you upload the imagesmto your computer and open them side by side you will see what we used to call GRAINS on the highest ISO images. Now it's called NOISE.
All this increase in sensitivity does not come free. There is a price to pay with your image appearing more noisy. See, when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject. Remember that an image sensor is still an ****og device and it generates its own noise, too! The increased sensitivity allows the image sensor to record more light signal and more noise. The ratio of light signal to noise (S/N ratio) determines the "noise" in your resultant image.
An image sensor is usually calibrated so that it gives the best image quality (greatest S/N ratio) at its lowest possible ISO speed. For most consumer digital cameras, this value will be expressed as ISO 50, ISO 64 or ISO 100. A few digital cameras use ISO 200 as their lowest ISO speed.
Just as with its film counterpart, an image sensor will exhibit "noise" (comparable to "graininess" in film) at the higher ISO speeds. Unlike film, where graininess can sometimes contribute to the mood of the image, noise produced by an image sensor is undesirable and appears as a motley of distracting coloured dots on your image.
To reduce NOISE there are some PS Plugins and also some Programs (I use Noiseware Community Edition - a free program that has it's full/more complete version for sale)
Now you ask... so WHY will I use this since it will only give me NOISE and I actually CAN'T control all the camera (when you change the ISO the camera will do it's part by changing automatically - most point and shoot will - it's apperture* and Film Speed*) - because you WILL gain some CONTROL of your pictures by turning the Flash OFF and increasing the ISO... now you will be able to take some pictures in some environments that DON'T NEED flash. Flash from PAS (point and Shoot) cameras are BAD... they give you too much shaddows, red eyes and black backgrounds... to day the least.
* we will learn more about this in future exercises
OBS.:
- I'm using my point and shoot instead of my DSLR so I can be in the same situation as most of you
- AFTER putting your camera into MANUAL but BEFORE taking the second shot (there should be 3) don't forget to turn the FLASH OFF - I want the 2 last pics without flash! The first will be decided by the camera, but most likely it will have a flash light, cause these cameras are too insecure :giggle: to trust on the photographer.
- This will probably work different for the girls using DSLR... so I will do this exercise in the DSLR version tomorrow - but in the meantime if you have a Point and Shoot join us here so you will start to learn the features of ALL cameras.
Now my examples... Mind you this are all SOOC (straigh out of the Camera images with no treatment)
http://farm4.static.flickr.com/3072/2657859651_c47fc43f35.jpg http://farm4.static.flickr.com/3064/2658685780_f676c90620.jpg
http://farm4.static.flickr.com/3174/2658686296_ca2d0e9a99.jpg http://farm4.static.flickr.com/3211/2658685906_d1c47a6242.jpg
http://farm3.static.flickr.com/2395/2658686426_f018b9b49c.jpg http://farm4.static.flickr.com/3260/2657859567_c98eba978c.jpg
and now see how the GRAIN/NOISE is different from the 100 and the 400:
http://farm3.static.flickr.com/2175/2657859943_eb570e2e25_o.jpg >>>ISO100 http://farm4.static.flickr.com/3132/2657859903_d230b66646_o.jpg >>>ISO400
OBS.: Mic I know you can't see the images I posted so if you want I can send you by e-mail.
Today we will learn about ISO, on further exercises we will return to this because as you will find out EVERYTHING on a camera is related... If you change one thing it affects all the others, but don't worry with practice this will all make sense in a while.
ISO sensitivity expresses the speed of photographic negative materials (formerly expressed as ASA).
Since digital cameras do not use film but use image sensors instead, the ISO equivalent is usually given.
What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.
And, where you would have needed to physically change to a different roll of film if you wanted a different ISO speed, digital technology allows you to simply dial one in. In this way, you can record images taken at different ISO speeds on the same memory card.
There is a lot more to this but with this information we can all start to change some things...
What are we going to do?
1) Place an object on some place with light (natural if possible) and take a photo of it in the AUTOMATIC mode.
2) Now with the same object and light I want you all to take your cameras and put it in the MANUAL mode (if you don't know where it is let me know and we can figure it out together - BTW ALL cameras have some sort of manual mode even the point and shoot ones). Try to find where the ISO option is (mine is in Manual/ISO) and put it in 100 - take a picture
3) With the same scene change now the ISO to the highest your camera allows (mine is 400) take the same shot...
4) I want all 3 images WITH the EXIF information posted in your post, PLEASE try to make the visible so everybody can see the different modes the camera used.
You will note that the EXPOSURE TIME from the ISO100 is very different than the other with the higher ISO and that the image with ISO100 does not have as much GRAIN/NOISE as the one with the higher ISO.
Next exercise we will learn more about Exposure Time
If you are using a point and shoot you will probably NOT SEE any changes... WHY? Because you don't have the full control of the point and shoot's BUT when you upload the imagesmto your computer and open them side by side you will see what we used to call GRAINS on the highest ISO images. Now it's called NOISE.
All this increase in sensitivity does not come free. There is a price to pay with your image appearing more noisy. See, when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject. Remember that an image sensor is still an ****og device and it generates its own noise, too! The increased sensitivity allows the image sensor to record more light signal and more noise. The ratio of light signal to noise (S/N ratio) determines the "noise" in your resultant image.
An image sensor is usually calibrated so that it gives the best image quality (greatest S/N ratio) at its lowest possible ISO speed. For most consumer digital cameras, this value will be expressed as ISO 50, ISO 64 or ISO 100. A few digital cameras use ISO 200 as their lowest ISO speed.
Just as with its film counterpart, an image sensor will exhibit "noise" (comparable to "graininess" in film) at the higher ISO speeds. Unlike film, where graininess can sometimes contribute to the mood of the image, noise produced by an image sensor is undesirable and appears as a motley of distracting coloured dots on your image.
To reduce NOISE there are some PS Plugins and also some Programs (I use Noiseware Community Edition - a free program that has it's full/more complete version for sale)
Now you ask... so WHY will I use this since it will only give me NOISE and I actually CAN'T control all the camera (when you change the ISO the camera will do it's part by changing automatically - most point and shoot will - it's apperture* and Film Speed*) - because you WILL gain some CONTROL of your pictures by turning the Flash OFF and increasing the ISO... now you will be able to take some pictures in some environments that DON'T NEED flash. Flash from PAS (point and Shoot) cameras are BAD... they give you too much shaddows, red eyes and black backgrounds... to day the least.
* we will learn more about this in future exercises
OBS.:
- I'm using my point and shoot instead of my DSLR so I can be in the same situation as most of you
- AFTER putting your camera into MANUAL but BEFORE taking the second shot (there should be 3) don't forget to turn the FLASH OFF - I want the 2 last pics without flash! The first will be decided by the camera, but most likely it will have a flash light, cause these cameras are too insecure :giggle: to trust on the photographer.
- This will probably work different for the girls using DSLR... so I will do this exercise in the DSLR version tomorrow - but in the meantime if you have a Point and Shoot join us here so you will start to learn the features of ALL cameras.
Now my examples... Mind you this are all SOOC (straigh out of the Camera images with no treatment)
http://farm4.static.flickr.com/3072/2657859651_c47fc43f35.jpg http://farm4.static.flickr.com/3064/2658685780_f676c90620.jpg
http://farm4.static.flickr.com/3174/2658686296_ca2d0e9a99.jpg http://farm4.static.flickr.com/3211/2658685906_d1c47a6242.jpg
http://farm3.static.flickr.com/2395/2658686426_f018b9b49c.jpg http://farm4.static.flickr.com/3260/2657859567_c98eba978c.jpg
and now see how the GRAIN/NOISE is different from the 100 and the 400:
http://farm3.static.flickr.com/2175/2657859943_eb570e2e25_o.jpg >>>ISO100 http://farm4.static.flickr.com/3132/2657859903_d230b66646_o.jpg >>>ISO400
OBS.: Mic I know you can't see the images I posted so if you want I can send you by e-mail.