Question about changing f stop exposure for class

Shyy said:

Shyy wrote:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Does my logic seem correct?

Click to expand...

trekkeruss said:

trekkeruss wrote:

trekkeruss said:

Shyy wrote:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Does my logic seem correct?

Click to expand...

You have the exposure reversed. If you want to underexpose, you want to let in less light. So for example, -1 stop, you want to close the aperture from f/2.0 to f.2.8. Or you opt for a faster shutter speed. If you want to overexpose, you want to let in more light. +1 would require opening the aperture (which is beyond what your lens is capable of) or slowing the shutter speed to 1/60.

Click to expand...

Shyy said:

Shyy wrote:

Hi guys,

I have a project for my photography class. We are using regular B&W film camera. For this project we have to show a subject in different exposure which shows 3 stops over and under exposed. My question is if my logic is correct.

Say I am using my Canon AE-1 Program and it meters and tells me the subject correct exposure is f2 at iso 400 with a shutter speed of 125. My prime lens f stop range goes from f2 to f4. To get the first 3 under exposed, I would use the following parameters.

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Shyy said:

-3 = would be a F0.7 but since my lens can only do f2 - I would change my shutter speed to three stop faster which is 1/1000?

Click to expand...

Shyy said:

-2 = would be a F1 but since my lens can only do f2 - I would change my shutter speed to two stop faster which is 1/500?

Click to expand...

Shyy said:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

Click to expand...

Shyy said:

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

Click to expand...

Shyy said:

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Click to expand...

Shyy said:

2 = 4, so I would just adjust it two stop to f4 with the shutter speed of 125

Click to expand...

Shyy said:

3 = 5.6, so I would just adjust it three stop to 5.6 with the shutter speed of 125

Click to expand...

Shyy said:

Does my logic seem correct?

Click to expand...

Shyy said:

Shyy wrote:

Would this now be correct?

-3 = would be a F5.6 but since my lens can only do f4 - I would change my shutter speed to one stop faster which is 1/250?

-2 = would be a F4 I would leave my shutter speed to 125

-1 = would be a F2.8 I would leave my shutter speed to 125

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

+1 = 1.4 but since my lens can only do f2 - I would change my shutter speed to one stop slower which is 1/60?

+2 = 1 but since my lens can only do f2 - I would change my shutter speed to two stop slower which is 1/30?

+3 = 0.7 but since my lens can only do f2 - I would change my shutter speed to three stop slower which is 1/15?

Click to expand...

Leonard Migliore said:

Leonard Migliore wrote:

Leonard Migliore said:

Shyy wrote:

Hi guys,

I have a project for my photography class. We are using regular B&W film camera. For this project we have to show a subject in different exposure which shows 3 stops over and under exposed. My question is if my logic is correct.

Say I am using my Canon AE-1 Program and it meters and tells me the subject correct exposure is f2 at iso 400 with a shutter speed of 125. My prime lens f stop range goes from f2 to f4. To get the first 3 under exposed, I would use the following parameters.

Click to expand...

Please explain "My prime lens f stop range goes from f2 to f4". I'm pretty sure your lens goes to f/16 and it may well go to f/22.

Leonard Migliore said:

-3 = would be a F0.7 but since my lens can only do f2 - I would change my shutter speed to three stop faster which is 1/1000?

Click to expand...

Have they bothered to teach you anything in this photography class? One of the first things that are taught about f/stops is that they are reciprocals. And the next thing is that the light that gets through a lens is reduced by the square of the f/stop.

Knowing this, you would discern that 3 stops under f/2 is f/5.6 (the traditional cadence of f/stops is 2,2.8,4.5.6,8,11,16,22). So 3 stops under 1/125 at 2 is 1/125 at 5.6.

Leonard Migliore said:

-2 = would be a F1 but since my lens can only do f2 - I would change my shutter speed to two stop faster which is 1/500?

Click to expand...

Again, leave the shutter speed the same and stop down 2 stops, or f/4.

Leonard Migliore said:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

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Guess.

Leonard Migliore said:

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

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That's your default exposure.

Leonard Migliore said:

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Click to expand...

Since f/stops are reciprocal, f/2.8 allows half the light that gets through at f/2. Leave the lens at f/2 and double your exposure time to 1/60.

Leonard Migliore said:

2 = 4, so I would just adjust it two stop to f4 with the shutter speed of 125

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Two stops over 1/125 at 2 is 1/30 at 2.

Leonard Migliore said:

3 = 5.6, so I would just adjust it three stop to 5.6 with the shutter speed of 125

Click to expand...

3 stops over 1/125 at 2 is 1/15 at 2

Leonard Migliore said:

Does my logic seem correct?

Click to expand...

I ain't seen no logic.

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trekkeruss said:

trekkeruss wrote:

trekkeruss said:

Shyy wrote:

Would this now be correct?

-3 = would be a F5.6 but since my lens can only do f4 - I would change my shutter speed to one stop faster which is 1/250?

-2 = would be a F4 I would leave my shutter speed to 125

-1 = would be a F2.8 I would leave my shutter speed to 125

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

+1 = 1.4 but since my lens can only do f2 - I would change my shutter speed to one stop slower which is 1/60?

+2 = 1 but since my lens can only do f2 - I would change my shutter speed to two stop slower which is 1/30?

+3 = 0.7 but since my lens can only do f2 - I would change my shutter speed to three stop slower which is 1/15?

Click to expand...

You can also adjust the ISO. So for +1, you could leave the aperture and shutter speed alone, and change the ISO to 200. For +2, you could have f/2.0, 1/60 and ISO 200 or f/2.0, 1/30, and ISO 400 or f/2.0, 1/125 and ISO 100.

Click to expand...

trekkeruss said:

trekkeruss wrote:

You can also adjust the ISO. So for +1, you could leave the aperture and shutter speed alone, and change the ISO to 200. For +2, you could have f/2.0, 1/60 and ISO 200 or f/2.0, 1/30, and ISO 400 or f/2.0, 1/125 and ISO 100.

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Tom_N said:

Tom_N wrote:

Tom_N said:

trekkeruss wrote:

You can also adjust the ISO. So for +1, you could leave the aperture and shutter speed alone, and change the ISO to 200. For +2, you could have f/2.0, 1/60 and ISO 200 or f/2.0, 1/30, and ISO 400 or f/2.0, 1/125 and ISO 100.

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The OP is using a film SLR. On that, changing the ISO setting will not affect the sensitivity of the sensor (film). It will only affect exposure indirectly...

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Tom_N said:

.... by causing the camera to modify the suggested aperture and shutter speed.

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Barrie Davis said:

Barrie Davis wrote:

Barrie Davis said:

Which modification is exactly what is required. In fact, changing ISO would be a very practical way to do it.

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Therefore, if using 400 ISO, shoot at 50, 100, 200, (400) 800, 1600, 3200 (seven frames, respectively.)

The difficulty comes from ascertaining which exposure is ABSOLUTELY CORRECT at 400, in order to establish the centre point of the whole bracket. Myself, I would recommend the use of an incident light meter, or (second best) metering from an 18% grey card in the same light as the subject.

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Barrie Davis said:

Barrie Davis wrote:

Barrie Davis said:

Barrie Davis wrote:

Barrie Davis said:

Which modification is exactly what is required. In fact, changing ISO would be a very practical way to do it.

Click to expand...

Therefore, if using 400 ISO, shoot at 50, 100, 200, (400) 800, 1600, 3200 (seven frames, respectively.)

The difficulty comes from ascertaining which exposure is ABSOLUTELY CORRECT at 400, in order to establish the centre point of the whole bracket. Myself, I would recommend the use of an incident light meter, or (second best) metering from an 18% grey card in the same light as the subject.

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Alternatively, shoot an even WIDER bracketed series, (9 or 11 frames, say) and from those use the seven frames which are best centred about the correct exposure, as chosen from the negatives when actually developed.

Note: You may get extra Brownie points for taking this empirical route to a successful project. (Photography is a practical art, so anything that works should be considered legitimate.)

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Shyy said:

Shyy wrote:

Shyy said:

trekkeruss wrote:

Shyy said:

Shyy wrote:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Does my logic seem correct?

Click to expand...

You have the exposure reversed. If you want to underexpose, you want to let in less light. So for example, -1 stop, you want to close the aperture from f/2.0 to f.2.8. Or you opt for a faster shutter speed. If you want to overexpose, you want to let in more light. +1 would require opening the aperture (which is beyond what your lens is capable of) or slowing the shutter speed to 1/60.

Click to expand...

Thanks! you are absolute correct, I just looked at my sheet for the project and I did reverse the information.

Would this now be correct?

-3 = would be a F5.6 but since my lens can only do f4 - I would change my shutter speed to one stop faster which is 1/250?

-2 = would be a F4 I would leave my shutter speed to 125

-1 = would be a F2.8 I would leave my shutter speed to 125

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

+1 = 1.4 but since my lens can only do f2 - I would change my shutter speed to one stop slower which is 1/60?

+2 = 1 but since my lens can only do f2 - I would change my shutter speed to two stop slower which is 1/30?

+3 = 0.7 but since my lens can only do f2 - I would change my shutter speed to three stop slower which is 1/15?

Click to expand...

dsjtecserv said:

dsjtecserv wrote:

dsjtecserv said:

Shyy wrote:

dsjtecserv said:

trekkeruss wrote:

dsjtecserv said:

Shyy wrote:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Does my logic seem correct?

Click to expand...

You have the exposure reversed. If you want to underexpose, you want to let in less light. So for example, -1 stop, you want to close the aperture from f/2.0 to f.2.8. Or you opt for a faster shutter speed. If you want to overexpose, you want to let in more light. +1 would require opening the aperture (which is beyond what your lens is capable of) or slowing the shutter speed to 1/60.

Click to expand...

Thanks! you are absolute correct, I just looked at my sheet for the project and I did reverse the information.

Would this now be correct?

-3 = would be a F5.6 but since my lens can only do f4 - I would change my shutter speed to one stop faster which is 1/250?

-2 = would be a F4 I would leave my shutter speed to 125

-1 = would be a F2.8 I would leave my shutter speed to 125

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

+1 = 1.4 but since my lens can only do f2 - I would change my shutter speed to one stop slower which is 1/60?

+2 = 1 but since my lens can only do f2 - I would change my shutter speed to two stop slower which is 1/30?

+3 = 0.7 but since my lens can only do f2 - I would change my shutter speed to three stop slower which is 1/15?

Click to expand...

Why do you say your lens can only do f/4? It may not be able to use f-numbers less than f/2, but it should have f-numbers beyond f/4, all the way up to f/16 to f/22. Can you explain?

Dave

Click to expand...

Shyy said:

Shyy wrote:

Shyy said:

dsjtecserv wrote:

Shyy said:

Shyy wrote:

Shyy said:

trekkeruss wrote:

Shyy said:

Shyy wrote:

-1 = would be a F1.4 but since my lens can only do f2 - I would change my shutter speed to one stop faster which is 1/250?

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

1 = 2.8, so I would just adjust it one stop to f2.8 with the shutter speed of 125

Does my logic seem correct?

Click to expand...

You have the exposure reversed. If you want to underexpose, you want to let in less light. So for example, -1 stop, you want to close the aperture from f/2.0 to f.2.8. Or you opt for a faster shutter speed. If you want to overexpose, you want to let in more light. +1 would require opening the aperture (which is beyond what your lens is capable of) or slowing the shutter speed to 1/60.

Click to expand...

Thanks! you are absolute correct, I just looked at my sheet for the project and I did reverse the information.

Would this now be correct?

-3 = would be a F5.6 but since my lens can only do f4 - I would change my shutter speed to one stop faster which is 1/250?

-2 = would be a F4 I would leave my shutter speed to 125

-1 = would be a F2.8 I would leave my shutter speed to 125

n = 2 from Canon's meter so I would leave it at f2 with the shutter speed of 125

+1 = 1.4 but since my lens can only do f2 - I would change my shutter speed to one stop slower which is 1/60?

+2 = 1 but since my lens can only do f2 - I would change my shutter speed to two stop slower which is 1/30?

+3 = 0.7 but since my lens can only do f2 - I would change my shutter speed to three stop slower which is 1/15?

Click to expand...

Why do you say your lens can only do f/4? It may not be able to use f-numbers less than f/2, but it should have f-numbers beyond f/4, all the way up to f/16 to f/22. Can you explain?

Dave

Click to expand...

Click to expand...

Member said:

MrMojo wrote:

1. Why are you required to use a B&W fllm camera?

2. What is the goal of the exercise i.e why 3 stops under/over exposure?

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Shyy said:

Shyy wrote:

Abit confused with the iso, is giing from ISO 100 to 200 to 300 considered each a full stop?

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ywjrh said:

Ted Kahn wrote:

ywjrh said:

Shyy wrote:

Abit confused with the iso, is giing from ISO 100 to 200 to 300 considered each a full stop?

Click to expand...

Click to expand...

ywjrh said:

A stop is always a factor of 2, so going from 100 to 200 is 1 stop, going from 100 to 400 is 2 stops, going from 100 to 800 is 3 stops, and so on.

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MarkInSF said:

MarkInSF wrote:

MarkInSF said:

MrMojo wrote:

1. Why are you required to use a B&W fllm camera?

2. What is the goal of the exercise i.e why 3 stops under/over exposure?

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Many photography classes are taught by Luddites. They think digital is a passing fad and only film is of lasting significance. They're idiots who require their students buy equipment they'll probably never use again and learn irrelevant skills when they could be doing something useful. Most are high school football coaches in real life. Or community college volleyball coaches.

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Member said:

MrMojo wrote:

1. Why are you required to use a B&W fllm camera?

2. What is the goal of the exercise i.e why 3 stops under/over exposure?

Click to expand...