# QUESTIONS:

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• 12-28-2011, 02:09 PM
ME Super
A short write up about the relationships between EV, ISO, f/stop and shutter speed.
When not doing flash photography, there are four things that determine whether a scene will be properly exposed. They are:

1. The amount of light falling on the scene (we'll call this Exposure Value (EV)).
2. The sensitivity (ISO) of the film.
3. The aperture (f/stop).
4. The shutter speed.

A bright sunny day has an EV of 15. The "Sunny f/16" rule says that correct exposure for this scene at f/16 is the closest reciprocal of the film speed. So for ISO 100 film, the correct exposure is 1/125 second at f/16. For ISO 200 film, the correct exposure is 1/250 second at f/16. For ISO 400 film, a correct exposure is 1/500 at f/16. For ISO 800 or 1000 film, 1/1000 second at f/16. Different scenes have different EVs. Open shade has an EV of 12. Sunsets are at EV 11. Brightly lit home interiors are at EV 6, average home interiors are at EV 5, nighttime scenes away from city lights and under a full moon are at EV -3.

There are many equivalent exposure values. Let's suppose that you've got ISO 400 film loaded in your camera, and your scene is an EV 15 scene. The following aperture/shutter speed combinations will give you correct, equivalent exposures (note that not all of these combinations may be available on your camera (for example, my camera's top shutter speed is 1/2000 second so the 1/4000 and 1/8000 second exposures are not available to me without filters, which is outside the scope of this post)):

• 1/250 second at f/22
• 1/500 second at f/16
• 1/1000 second at f/11
• 1/2000 second at f/8
• 1/4000 second at f/5.6
• 1/8000 second at f/4

For a good write-up about exposure when you don't have a light meter handy, along with two handy charts to calculate f/stop and shutter speed combinations for a given scene, Fred Parker has a good write-up at http://www.fredparker.com/ultexp1.htm.

Flash photography is a different beast. Every flash has a guide number. My camera's built-in flash's guide number is 42 at ISO 100. Consult your camera and/or flash manual for your flash's guide number. Guide numbers vary with film speed. With flash photography, shutter speed is less of an issue as long as it is no faster than your flash sync speed (consult your camera's manual to find the flash sync speed). For straight flash photography, divide your flash's guide number at the ISO you are using (remember, guide numbers vary with film speed) by the camera-to-subject distance. This will give you the f/stop to use to take the photo. For example, if my camera is loaded with ISO 100 film, and my flash's guide number is 42, and my camera-to-subject distance is 10 feet, then 42/10=4.2. I can set my aperture to f/4 and my subject will be properly exposed.

Note that guide numbers can be given in feet or meters. My camera's manual actually gives me the guide numbers in meters but I'm used to working in feet. Multiply meters by 3.28 to get feet, or divide feet by 3.28 to get meters.

I hope this helps without confusing you.
ME Super
• 12-28-2011, 02:16 PM
keithwms
Quote:

Originally Posted by ME Super
When not doing flash photography, there are four things that determine whether a scene will be properly exposed. They are:

1. The amount of light falling on the scene (we'll call this Exposure Value (EV)).
2. The sensitivity (ISO) of the film.
3. The aperture (f/stop).
4. The shutter speed.

Not to be pedantic, especially after your informative post, but I would add three more, for more advanced shooters ;)

1. Bellows factor
2. Filter factor
3. Reciprocity factor
• 12-28-2011, 02:21 PM
pbromaghin
This web page in the link below - one single page - contains all the basic information that you are now asking for. There is a chart there that explains exposure in the context of the "Sunny 16" rule. Read the web page and print out the chart and carry it with you whenever you carry a camera. If you follow its guidance, you will *always* produce reasonably well-exposed photographs.

http://www.fredparker.com/ultexp1.htm

Your Pentax is a pretty modern model with fairly advanced electronics inside. It reads a code on the film when you load it and sets the ISO for you.

Second the recommendation to get a book on basic photography. Despite what you say about all the reading you have done, you are asking the questions that would be asked only by someone who has either not done any reading, or did and understood none of it.

Edit to add: the web page takes the same basic theme of MESuper's excellent post into greater detail.
2nd edit to add: Same page. Forget what I said, just listen to him. He knows more and has more patience than I do, anyway.
• 12-28-2011, 03:19 PM
ME Super
Right. I did not go into filter factor, bellows factor, or reciprocity factor. Those were beyond the scope of my post. And yes, do visit the web page. It explains in much more detail how exposure works. Print the charts and follow them as they cover most of the situations you will encounter.

I've also found it useful to put the palm of my hand in the same light as my subject, meter off of it, and open one stop. This works well for photographers with caucasian skin. It's a "poor man's incident meter". For those with different skin tone than caucasians, YMMV.
• 12-28-2011, 07:36 PM
amundenovskiy
Quote:

Originally Posted by E. von Hoegh
Get and read a manual for the Mamiya. Yes, there is a difference between 200ASA and 400ASA film. You really should get and study a book on basic photography, it will help answer many of the questions you post here. Do some homework.

I think u miss understood me, I know the difference in 200ASA and 400ASA... I was asking would there be a difference in the 400, if the 200 said to use 4.8f-stop for inside conditions. for the 400ASA..... o.O
• 12-28-2011, 07:40 PM
JBrunner
Quote:

Originally Posted by amundenovskiy
I think u miss understood me, I know the difference in 200ASA and 400ASA... I was asking would there be a difference in the 400, if the 200 said to use 4.8f-stop for inside conditions. for the 400ASA..... o.O

Yes, 1 stop, about a third under 5.6.
• 12-28-2011, 07:43 PM
amundenovskiy
My question in this matter has since been answered - so thank you everyone, even tho Im sure I tested some patients for some people that were educated, blah blah blah in this area. But like I said if a photographer can't help a newbie then how can he expect to be good at his own work?
Anyway I have to download old copies of my camera's manuals since I don't have a single one! :(

Quote:

Originally Posted by ME Super
When not doing flash photography, there are four things that determine whether a scene will be properly exposed. They are:

1. The amount of light falling on the scene (we'll call this Exposure Value (EV)).
2. The sensitivity (ISO) of the film.
3. The aperture (f/stop).
4. The shutter speed.

A bright sunny day has an EV of 15. The "Sunny f/16" rule says that correct exposure for this scene at f/16 is the closest reciprocal of the film speed. So for ISO 100 film, the correct exposure is 1/125 second at f/16. For ISO 200 film, the correct exposure is 1/250 second at f/16. For ISO 400 film, a correct exposure is 1/500 at f/16. For ISO 800 or 1000 film, 1/1000 second at f/16. Different scenes have different EVs. Open shade has an EV of 12. Sunsets are at EV 11. Brightly lit home interiors are at EV 6, average home interiors are at EV 5, nighttime scenes away from city lights and under a full moon are at EV -3.

There are many equivalent exposure values. Let's suppose that you've got ISO 400 film loaded in your camera, and your scene is an EV 15 scene. The following aperture/shutter speed combinations will give you correct, equivalent exposures (note that not all of these combinations may be available on your camera (for example, my camera's top shutter speed is 1/2000 second so the 1/4000 and 1/8000 second exposures are not available to me without filters, which is outside the scope of this post)):

• 1/250 second at f/22
• 1/500 second at f/16
• 1/1000 second at f/11
• 1/2000 second at f/8
• 1/4000 second at f/5.6
• 1/8000 second at f/4

For a good write-up about exposure when you don't have a light meter handy, along with two handy charts to calculate f/stop and shutter speed combinations for a given scene, Fred Parker has a good write-up at http://www.fredparker.com/ultexp1.htm.

Flash photography is a different beast. Every flash has a guide number. My camera's built-in flash's guide number is 42 at ISO 100. Consult your camera and/or flash manual for your flash's guide number. Guide numbers vary with film speed. With flash photography, shutter speed is less of an issue as long as it is no faster than your flash sync speed (consult your camera's manual to find the flash sync speed). For straight flash photography, divide your flash's guide number at the ISO you are using (remember, guide numbers vary with film speed) by the camera-to-subject distance. This will give you the f/stop to use to take the photo. For example, if my camera is loaded with ISO 100 film, and my flash's guide number is 42, and my camera-to-subject distance is 10 feet, then 42/10=4.2. I can set my aperture to f/4 and my subject will be properly exposed.

Note that guide numbers can be given in feet or meters. My camera's manual actually gives me the guide numbers in meters but I'm used to working in feet. Multiply meters by 3.28 to get feet, or divide feet by 3.28 to get meters.

I hope this helps without confusing you.
ME Super

• 12-28-2011, 07:46 PM
JBrunner
1 stop is the difference between 200 and 400. One more stop than 400 would be 800. One less stop than 200 would be 100. Everything in photography is half and double. Twice 200 is 400, half 200 is 100. Both are 1 stop. Twice 5.6 is 8. Half 5.6 is 4. Both are 1 stop. Twice 1/125 is 1/250. Half is 1/60. Both are one stop. All three legs make the stool. Capiche?
• 12-28-2011, 09:24 PM
zsas
Ohhhhh fully manual camera (Mamiya Sekor), very nice to hear! That will be an excellent camera to learn on! You set the ISO (same as ASA) manually based on your film (note DIN or the Deutsche system is phased out and we genenlly don't talk in DIN scale anymore), adjust aperture and shutter speed based on light meter reading (hope your light meter is still working) and you are set! That sounds like an outstanding camera! Your other sounds like a great kit too but learning on a fixed lens (non-zoom) is often very nice so you can focus on composition and your body position to zoom, the most pure analog, IMO. Happy holidays to you too, you will have a ball shooting film!
• 12-29-2011, 10:17 AM
E. von Hoegh
Quote:

Originally Posted by amundenovskiy
I think u miss understood me, I know the difference in 200ASA and 400ASA... I was asking would there be a difference in the 400, if the 200 said to use 4.8f-stop for inside conditions. for the 400ASA..... o.O

No, you don't know the difference. If you did know the difference, you wouldn't have asked the question.

As far as misunderstanding goes, your writing is difficult to decipher.

As I said, do your homework. Don't expect us to do it for you. I can't speak for others, but I am happy to share whatever knowledge I might have, as long as you make some effort to inform yourself. Don't expect us to spoon feed you things you can learn on your own.
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