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09-12-2011, 09:24 PM   #1
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Exposure question

Hi guys,
I have just joined this forum and this is my first post. I am a newbie and I have two questions.
1. Under the same conditions and exposure, which mode will you shoot, Aperture or shutter priority? The reason why I ask is that in the end you still have the same exposure anyway, so what does it matter.
2. I set my ISO to auto-iso, so that i dont have to worry about it. but sometimes i realise that it wont go to the highest ISO range to increase the shutter speed. How does the ISO range work. what takes priority in this situation?

09-12-2011, 09:33 PM   #2
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I shoot in Hyper-program (P) mode most of the time. When I nedd to shoot some dynamic pictures (ie action), I use shutter priority. I rarefly use aperture priority, although I am aware that a number of Pentaxians do.

Just my own limited experience...
09-12-2011, 09:48 PM   #3
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I can address the first question. There is a big difference between Av and Tv mode. Understand that there are many different aperture shutter speed combinations for a given lighting situation. The exposure will be the same however the look can be very different. With larger apertures (smaller f numbers) you will get shallower depth of field in the image with a faster shutter speed. But if you want more depth of field you will need to use a smaller aperture with slower shutter speeds. So you use Av to control depth of field. You can use Tv to control the way you want to express movement in an image. I really only use Tv to set speed when there is an action seen and I want to stop any motion blur. Some intentionally use longer shutter speeds with a tripod to use blur to express movement. The best example is images of rivers and waterfalls. This is a very simple answer to a very important fundamental aspect of photography. Someone will invariably recommend Bryan Peterson's book Understanding Exposure. It is a good book to begin building your understanding of the so called triangle of exposure where shutter speed ,aperture, and ISO interrelate to make an exposure.

I don't use auto ISO. So I will defer to others.
09-12-2011, 09:49 PM   #4
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You can get the same exposure using *any* mode. The only difference is which mode allows you to get the specific combination of shutter speed and aperture you want in the most natural way for the way you think, with the least amount of intervention.

09-12-2011, 09:54 PM - 1 Like   #5
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You may have the same exposure by changing aperture and shutter speed but you will have very different photos. Aperture controls depth of field, which can give you a lot of creative control. Here's a wide aperture setting photo I took yesteday.



f4 1/1000 ISO 400

Shutter speed controls how much motion you can freeze. Notice how sharp the tree is even though there was a stiff breeze. (with no PP sharpening) Slow shutter speeds will blur your photo. Fast ones will help stop blur. You still have to hold your camera reasonably steady. With sports or action you will generally want a fast shutter speed, though deliberate blurs can be creatively useful.

I'm not a fan of auto ISO except when shooting with poor light or needing to stop motion. The higher the ISO the less dynamic range and the more noise your photos will have. Depending on your camera there will be a different maximum ISO for high quality images. The newest model like the Kr, Kx and K-5 can handle higher ISO than older cameras or point and shoots.

When shooting birds, I will go up to ISO 400 with my K-5 and still get great image files. My K20d has noticeably less dynamic range at 400 ISO. When shooting landscapes I will try for 100 ISO if it isn't windy. There is a difference in image quality. When I put the camera away, I set it for Av with f8 and 200 ISO, which gives me the best compromise between quality and the ability to just grab the camera and take a quick shot.

Last edited by mysticcowboy; 09-12-2011 at 09:59 PM.
09-12-2011, 09:58 PM   #6
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Howdy! Choosing modes and exposure settings depend on what effects we want.

We use Av (aperture priority) often with manual lenses, or when we know we want a certain DOF (depth of field) in a picture. We may use a wide aperture like f/1.7 if we want to really separate a subject from their surroundings via thin DOF, or a tight aperture like f/11 if we want thick DOF where everything is sharp.

We use Tv (shutter priority) when shutter speed is important. We may use a slow shutter like 1/10 in very low light or if we want to capture motion blur like moving water. We'll use a fast shutter like 1/1000 for action sports or just in very bright light. And we use Sv (sensitivity | ISO priority) when we want to maintain a consistent noise level in a series of shots, or when we know that a certain ISO is needed for a shot.

You didn't say what camera you have. Some Pentax dSLRs also have TAv (shutter+aperture) priority mode, where if we know that we want both a certain DOF and a certain shutter speed for capturing action, we can set those and let the ISO float to whatever level is needed to make the exposure.

The Auto-ISO range depends on what you've set. Look in your manual to see how to change that range. We generally keep the ISO low if we want great detail and low noise in pictures, or higher if we know that the speed is necessary for action or low-light shots. Depending on what mode you're in, for low-light shots the camera will first try to lower the shutter speed, then try to raise the ISO. By choosing a priority mode, you control which of those is first.

Hope this helps. Good luck!
09-12-2011, 10:00 PM   #7
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Thanks for the quick reply. I do understand basically what you guys are saying. what my mind can seem to comprehen is that if my f-stop is 2.0 and the shutter speed is 1/ 90s. under the same condition and exposure shouldnt i get the same values no matter which priority i choose. doesnt that automatically translate that I will get the same depth of field?
09-12-2011, 10:11 PM   #8
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Yeah I understand what you guys are saying. and basically that is the way I shoot. I do shoot mainly in Av mode. The problem that my mind cant seem to comprehend is that if say your f-stop is 2.0 and shutter speed is 1/90. Under the same condition and exposure shouldnt you get the same values whether in Av or Tv mode.

Am I wrong to think this?

09-12-2011, 10:13 PM   #9
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QuoteOriginally posted by Culture Quote
Hi guys,
I have just joined this forum and this is my first post. I am a newbie and I have two questions.
1. Under the same conditions and exposure, which mode will you shoot, Aperture or shutter priority? The reason why I ask is that in the end you still have the same exposure anyway, so what does it matter.
2. I set my ISO to auto-iso, so that i dont have to worry about it. but sometimes i realise that it wont go to the highest ISO range to increase the shutter speed. How does the ISO range work. what takes priority in this situation?
I stay in Aperture Priority mode even when I shouldn't. Sometimes I realize I am working too hard, trying to control shutter speed by figuring out in my head how many stops to change the aperture to get a particular shutter speed. Then I remember the camera has a mode that does it for me.

The mode you use should be something you are completely comfortable in, and allow you to quickly access the things you want the most control over. All modes can be forced to come up with the same exposure values, with more or less work. But if you want to change something for your next shot, you want a mode that avoids fumbling or taking your eye from the viewfinder. So think about what setting you want to control, what setting won't affect the photo a lot, what would work OK on Auto, and then choose a mode for that. You should check the manual or take a few shots to confirm how your new mode works. Comfort will come with practice.

Auto ISO works a little differently with each camera generation. The upper-tier models like the K-7 allow you to influence when it decides to raise ISO.

[Edit] OK, I figured out you have the K-m. You have the option to set the range of ISOs the camera can use, p. 87 in your manual. You can set the camera to use full or half-stops when it's choosing an ISO (p. 78). Your camera won't do Auto ISO in Manual Mode. Scene modes will use their own logic for ISO and Bulb mode will make it drop to the lowest possible value. The other choices it makes are kind of obscure and you can't control them. One thing it will do is try to follow the rule for keeping shutter speed in the handheld range. So if you're in Av, Auto ISO with the kit lens at 30mm and choose an aperture that would drop shutter speed, the camera will bump ISO to keep the shuttter speed in handheld range. A lot of people complain that with a flash, Auto ISO goes to the maximum ISO. I'm not sure what the K-m does here.

Last edited by Just1MoreDave; 09-12-2011 at 10:30 PM.
09-12-2011, 10:15 PM   #10
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QuoteOriginally posted by Marc Sabatella Quote
You can get the same exposure using *any* mode. The only difference is which mode allows you to get the specific combination of shutter speed and aperture you want in the most natural way for the way you think, with the least amount of intervention.
Yeah and that is my problem. sometimes you just dont have the time to switching between modes and finding the right exposure.
The moment will already be gone. I am trying to reduce that it takes to get the setting right to shooting.
09-12-2011, 10:17 PM   #11
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QuoteOriginally posted by RioRico Quote
Howdy! Choosing modes and exposure settings depend on what effects we want.

We use Av (aperture priority) often with manual lenses, or when we know we want a certain DOF (depth of field) in a picture. We may use a wide aperture like f/1.7 if we want to really separate a subject from their surroundings via thin DOF, or a tight aperture like f/11 if we want thick DOF where everything is sharp.

We use Tv (shutter priority) when shutter speed is important. We may use a slow shutter like 1/10 in very low light or if we want to capture motion blur like moving water. We'll use a fast shutter like 1/1000 for action sports or just in very bright light. And we use Sv (sensitivity | ISO priority) when we want to maintain a consistent noise level in a series of shots, or when we know that a certain ISO is needed for a shot.

You didn't say what camera you have. Some Pentax dSLRs also have TAv (shutter+aperture) priority mode, where if we know that we want both a certain DOF and a certain shutter speed for capturing action, we can set those and let the ISO float to whatever level is needed to make the exposure.

The Auto-ISO range depends on what you've set. Look in your manual to see how to change that range. We generally keep the ISO low if we want great detail and low noise in pictures, or higher if we know that the speed is necessary for action or low-light shots. Depending on what mode you're in, for low-light shots the camera will first try to lower the shutter speed, then try to raise the ISO. By choosing a priority mode, you control which of those is first.

Hope this helps. Good luck!
Thanks for the explaination. It was good information. I am using a K-M
09-12-2011, 10:44 PM   #12
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QuoteOriginally posted by Culture Quote
Yeah and that is my problem. sometimes you just dont have the time to switching between modes and finding the right exposure.
The moment will already be gone. I am trying to reduce that it takes to get the setting right to shooting.
In dynamic situation, I often just stay in P mode with AF lenses. (MFL's take different techniques.) My rule here is: GET THE FOCUS RIGHT; EVERYTHING ELSE CAN BE FIXED IN PP.

Getting the exposure partly depends on the metering mode: spot or center-weighted or matrix. If lighting is weird and the subject is of moderate tone (close to 20% grey) then I'll use spot-metering and make sure the subject is tightly centered. I also chimp a lot when time allows, so can see how an exposure went and make necessary adjustments. That's the best part of digital: instant replay. Instant feedback. Fix it as you go.

For a series of shots under fairly consistent lighting, I'll often go to M(anual) mode, take a reading, adjust as needed, and stay there. For shots where I can't get a good reading off the subject, I'll meter (spot or center-weighted) off something of a similar tone, like the ground or my hand or sleeve. And when it really matters, I bracket bracket bracket! IMHO metering technique and bracketing are as important (or more so) than the precise mode used.
09-12-2011, 11:51 PM   #13
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QuoteOriginally posted by RioRico Quote
In dynamic situation, I often just stay in P mode with AF lenses. (MFL's take different techniques.) My rule here is: GET THE FOCUS RIGHT; EVERYTHING ELSE CAN BE FIXED IN PP.

Getting the exposure partly depends on the metering mode: spot or center-weighted or matrix. If lighting is weird and the subject is of moderate tone (close to 20% grey) then I'll use spot-metering and make sure the subject is tightly centered. I also chimp a lot when time allows, so can see how an exposure went and make necessary adjustments. That's the best part of digital: instant replay. Instant feedback. Fix it as you go.

For a series of shots under fairly consistent lighting, I'll often go to M(anual) mode, take a reading, adjust as needed, and stay there. For shots where I can't get a good reading off the subject, I'll meter (spot or center-weighted) off something of a similar tone, like the ground or my hand or sleeve. And when it really matters, I bracket bracket bracket! IMHO metering technique and bracketing are as important (or more so) than the precise mode used.
How long does it take you to do all of these? I know that with time things will be better.

Now dont get me wrong. when the time is good and i have the time I can make the settings. but when time is not on my side then panic sets in. That is what I hate.
09-12-2011, 11:58 PM   #14
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QuoteOriginally posted by mysticcowboy Quote
You may have the same exposure by changing aperture and shutter speed but you will have very different photos. Aperture controls depth of field, which can give you a lot of creative control. Here's a wide aperture setting photo I took yesteday.



f4 1/1000 ISO 400

Shutter speed controls how much motion you can freeze. Notice how sharp the tree is even though there was a stiff breeze. (with no PP sharpening) Slow shutter speeds will blur your photo. Fast ones will help stop blur. You still have to hold your camera reasonably steady. With sports or action you will generally want a fast shutter speed, though deliberate blurs can be creatively useful.

I'm not a fan of auto ISO except when shooting with poor light or needing to stop motion. The higher the ISO the less dynamic range and the more noise your photos will have. Depending on your camera there will be a different maximum ISO for high quality images. The newest model like the Kr, Kx and K-5 can handle higher ISO than older cameras or point and shoots.

When shooting birds, I will go up to ISO 400 with my K-5 and still get great image files. My K20d has noticeably less dynamic range at 400 ISO. When shooting landscapes I will try for 100 ISO if it isn't windy. There is a difference in image quality. When I put the camera away, I set it for Av with f8 and 200 ISO, which gives me the best compromise between quality and the ability to just grab the camera and take a quick shot.
Nice shot. I like the bokeh. I took some shots myself yesterday. when I get the chance I will upload them.
The question i had was something that has been on my mind but yesterday i was shooting "the light at the end of a tunnel" thingy and i couldnt figure out what mode i should shoot.
Tv was what i thought will be good but i didnt have enough time with my setting and the lights came on. damn.
09-13-2011, 01:44 AM   #15
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QuoteOriginally posted by Culture Quote
QuoteOriginally posted by RioRico:
For a series of shots under fairly consistent lighting, I'll often go to M(anual) mode, take a reading, adjust as needed, and stay there. For shots where I can't get a good reading off the subject, I'll meter (spot or center-weighted) off something of a similar tone, like the ground or my hand or sleeve. And when it really matters, I bracket bracket bracket! IMHO metering technique and bracketing are as important (or more so) than the precise mode used.
How long does it take you to do all of these?
Hardly any time at all! In M mode, punching the Green button is fast. In an Auto mode, punching the AE-L button is fast. I mean like one second. Setting bracketing takes a little longer, like 3-5 seconds -- and on my K20D in RAW, there's a 3-second write delay after shooting. Chimping is slightly slower but requires more brainpower, which I sometimes lack. Duh...

QuoteQuote:
Now dont get me wrong. when the time is good and i have the time I can make the settings. but when time is not on my side then panic sets in. That is what I hate.
Spray and pray!

Back in the day, my main camera for awhile was an ancient folder, a German 1934 Kodak Retina 1, the very first 135 camera. With a great 50/3.5 lens, manual shutter, no rangefinder, no metering, no nothing but focus-shutter-aperture controls. After a couple intensive months, it became totally instinctive. Look at a scene, judge the distance and light -- then my fingers automatically made the adjustments, and I shot. And turned the film knob; no quick-advance lever either! A light-meter in my pocket, just in case, but otherwise it's all a matter of experience. Look, diddle, shoot, nice and easy!

My point is: don't panic. Learn to judge scenes. For exposure, remember that you're not capturing subjects, you're capturing LIGHT -- so learn to judge light and shadow. With an AF lens and the camera in P mode and center-weighted metering, you should be able to look at a subject and judge whether you need to tweak the EV compensation. Then shoot and chimp and adjust and shoot again. And if you're in a hurry and get the exposure wrong, well, it can be fixed in PP.
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