ISO, noisy photos, and things of that nature...

First things first! Wanted to apologize for slightly lengthy posts for the first few blog entries. They should be shorter for future posts, but I first need to lay the groundwork for the basics of photography which require a bit more explanation, and thus longer posts. Thanks for your patience!

Todays topic is ISO. I'll discuss what it is, when to increase it, and the negative effects it can have.

I'm going to start by just copying and pasting my prior written definition from my second blog post...

"ISO - or International Organization for Standardization, refers to the sensors sensitivity to a given amount of light. This relates to film speed in non-digital cameras. The higher the number the faster the film. 100 being low speed, and 800 or more considered high speed film. By increasing the sensitivity of the image sensor, you are making it more sensitive to a given amount of light. So for example lets say you need to take a photograph in a dark room. You may start by trying to make the aperture it's largest possible size to let the most light reach the sensor. You may then try to make the shutter speed longer to get the light you need. Well if you have the shutter speed to slow (or open longer) you may capture the image at a proper exposure but your image will likely be blurred if you were hand holding the camera (as opposed to mounting it on a tripod). So what can you do about that? Increase the sensitivity of the sensor. By bumping up the ISO to a higher number, one can shoot at a shutter speed that wont cause any motion blur. Without adjusting the ISO, the image will look dark and underexposed. By increasing the ISO, the light that is available in the room will seem more apparent in your photos because of the increased sensitivity to light."

So we now know that if a situation occurs where it is dark and we need to handhold our camera for a shot, we can bump up the ISO to allow us to shoot at a faster shutter speed as to not blur the photo. Increasing ISO may also prove useful if you have a situation in lower light conditions where you would otherwise already have a fast enough shutter speed for handholding, but your subject is actually moving which may require an even faster shutter speed. Below is an example of this type of situation:

I was photographing a bridge opening on the York River where a boat was passing through the bridge. In the first photo I wanted to show the blur of the boat. At an shutter speed of 30 seconds, all you see is the blur of the lights from the boat. For the second photo I needed to freeze the movement of the boat so that you could still tell what it was. I quickly bumped up my ISO so that I could hopefully freeze the action. The photo didn't turn out all that well, but I think it helps demonstrate the concept (oh, and I had to use a tripod for the first photo in order to keep the bridge sharp because it's humanly impossible to handhold an exposure of 30 seconds)-

ISO-100, 30 seconds, F/9

ISO-3200, 1/4 second, F/2.8 - In this case I should have shot at an even faster shutter speed and a higher ISO to compensate. However, I was trying to avoid image noise as much as possible. We'll get into that in just a minute.

Similar to yesterdays post, I want to give you a stop chart to show what amounts of ISO represent one full stop of light.

• Low ISO, Less image noise, Lower sensitivity to light
• ISO-100
• ISO-200
• ISO-400
• ISO-800
• ISO-1600
• ISO-3200
• ISO-6400
• ISO-12800
• High ISO, More image noise, Greater sensitivity to light

it should be noted that your camera may have ISO settings between the ones listed above. again, many cameras let you increase or decrease your ISO in 1/3 stops of light where those listed above are full stops. if your camera allows 1/3 increments, 3 clicks of the ISO setting wheel will increase or decrease your ISO 1 full stop.

So now we've added a third and final way to adjust our exposure. Let's say we have our settings in such a way that your photo is properly exposed by only changing aperture and shutter speed. You can then increase or decrease your ISO one full stop and would in return have to increase one of the other two settings one full stop to maintain the same original exposure.

Example 1: ISO-100, F/5.6, 1/125

You can increase the ISO one full stop to ISO-200 (see chart above) and then change either the aperture or shutter speed one full stop. So let's increase the shutter speed for this example.

New settings: ISO-200, F/5.6, 1/250th second

Example 2: ISO-100, F/8, 1/250th

You can increase the ISO let's say 3 full stops and then decrease the aperture (or make the hole smaller to compensate for the increased sensitivity to light) 3 full stops.

New settings: ISO-800, F/22, 1/250th

In both examples you were able to change settings and end up with the same exposure.

So I'm hoping at this point you're starting to get the concept of ISO and how it effects your photograph. In that last photo, and in the chart above, you may have noticed the comments regarding image noise. What is image noise? Image noise is a negative side effect of increasing the ISO. The more you increase the ISO, the more image noise or graininess you'll notice in your photos (especially in the shadow areas).

Examples of noise at different full stop ISO settings (missing ISO-6400, accidently deleted it before uploading..again, I think you still get the idea though). In these examples I changed the shutter speed accordingly to maintain the same exposure when I adjusted the ISO. I left aperture the same for each photo.

ISO-100

ISO-200

ISO-400

ISO-800

ISO-1600

ISO-3200

ISO-12800

It should be noted that the greater the ISO and noise level, the less sharp your image will be. You can also reduce the noise in post processing with noise reduction software, but that's another days topic. If you want to get a jumpstart though, one of the best programs for this is called Noise Ninja.

So that's ISO in a nutshell. It can be a bit confusing, but the best way to learn it is use this guide and go out and play with the settings. Just remember if you've got your slowest possible shutter speed that you can hand hold and your widest aperture for the most light and you still can't get enough light....increase the ISO until you get a properly exposed photo.

There's your ISO "From The Ground Up!"

View the full post here...

Aperture & Shutter Speed (A Beautiful Relationship)

So today I want to hit a bit more on aperture and shutter speed.

As I said in the last post...

Aperture = Size of hole in the lens. Bigger hole equals more light. Smaller hole means less light. Bigger hole means shallower depth of field (less in focus in front of and behind your subject). Smaller hole means larger depth of field (more in focus in front of and behind your subject).

Lets add a bit to what we've already learned. The size of the aperture is referred to as an F-stop.

This is the confusing part... This will be tough for many people to wrap your heads around. I know it was for me at first

The larger the F-stop number (ex. F/22), the smaller the hole opening.

The smaller the F-stop number (ex. F/2.8), the larger the hole opening.

Let's lay this out in a table of sorts:

• Little number, Shallow DOF, More light
• F/2.8
• F/4
• F/5.6
• F/8
• F/11
• F/16
• F/22
• Big number, Large DOF, Less light

if you set your camera to manual and read the instructions on how to change aperture...

scroll through the numbers by changing the aperture. you'll notice there are other numbers between these that I have listed. i didn't list them because the numbers above are 1 full stop of light each. just know that you can change the F/number in smaller increments perhaps 1/3 a stop by using one of these other numbers.

So now what is a stop or an F stop?

A stop is how we measure how much light is being allowed to hit the sensor through the cameras aperture.

So lets say we shot a photo and it was really bright and overexposed. One way of fixing this is changing the size of the aperture, perhaps reducing it one stop of light (meaning a bigger F/number). This would in turn reduce the size of the aperture opening allowing less light to reach the sensor.

Shutter Speed - Length of time the shutter is open allowing a given amount of light to pass through the aperture opening to your cameras sensor. Slower shutter speed means more light. Faster shutter speed means less light. Slower shutter speed blurs movement. Faster shutter speed freezes the movement.

Again with the confusing part. When referring to shutter speed, a seemingly large number (1/1000) is actually a lesser amount of time than a seemingly smaller number (1/15). One one thousandths of a second is a very short period of time whereas one fifteenth of a second is a considerably longer amount of time. Keep this in mind.

• Small Number, Shorter period of time, Less light, Freezes action
• 1/1000 of a second
• 1/500
• 1/250
• 1/125
• 1/60
• 1/30
• 1/15
• 1/2
• 1 second
• Bigger number, Longer period of time, More light, Blurs movement

again each number in the table above represents one full stop of light. your camera settings will likely show numbers between these numbers but they are in increments of 1/3 of a stop.

So how does aperture and shutter speed relate to each other. It's rather genius really...

To keep a set exposure, but change the artistic effects, you can change either the aperture or shutter speed to reach the desired effect. If you change either of these things you will throw your exposure off soooooo: If you reduced the aperture by one stop to get a desired effect, you can increase the shutter speed by one stop to maintain the proper exposure. So what you do to one, you have to do the opposite to the other!!

Lets say you have a photo where you've nailed down the exposure. It's really great. The only problem is that the photo is blurring the movement and you really want to capture that car moving by freezing the action:

Sample Settings for desired exposure: 1/30th second & F/11

If you refer to the above table you'll see that you change your shutter speed to something more suitable for a moving car say... 1/250th of a second. That's 3 stops of light. You must then drop the F/stop down by 3 stops. The trusty table above will show the appropriate F/number to maintain your exposure is F/4.

We've just changed the artistic effect without hindering our desired exposure.

Another example:

You have a portrait and you'd like the background to be blurrier or more out of focus (OOF).

Current settings: 1/30th second & F/8

We want to make the f-number smaller or the hole larger (don't forget that trickery). To do this we may stop down the F-number to something like F/4. Conveniently F/4 is exactly 2 stops of light less than F/8. To maintain our desired exposure we should then increase the shutter speed by two stops. Trusty table above says 2 stops of light difference would be 1/125th of a second.

So again we've changed the artistic effect without changing our shutter speed.

it should also be noted that since your camera allows you to choose stops in 1/3 increments as mentioned above....three clicks of the wheel in either direction would adjust your setting 1 full stop. so if you want to decrease you're aperture one full stop you'd click the aperture wheel 3 clicks to the left. in turn, you'd click the shutter speed wheel 3 clicks to the right to maintain that desired exposure.

To wrap this up, let's take a glance at a few examples of the artistic effects available with aperture and shutter speed.

Desired Effect: Blur everything closer than and beyond our focal point (the little knob sticking out of the tree). We need a large aperture opening to gain the desired effect aka a small F/number.

F/4, 1/80th second

Desired effect: Subject (people) and background in focus. We need a small aperture opening (large number) to gain this desired effect.

F/22, 1/100th second

Desired effect: Freeze the action. We need a fast shutter speed.

F/2.8 1/4000th second

Desired Effect: Blur the movement. We need a slower or longer shutter speed.

F/4.5, 1/25th second

In conclusion: Whatever you change in either aperture or shutter speed, you must then change the other in the opposite direction to maintain a desired exposure.

This has been aperture and shutter speed "From The Ground Up!"

View the full post here...