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Old Aug 12, 2006, 8:43 AM   #1
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If you want to take blur-free low light handheld and without flash photos, here is a "VR" tweak article I wrote after conducting some test with my 7900.

Sample Photos using this tweak, here:

http://www.coolpix7900.com/Gallery/t...s.php?album=32



Full article explaining the " VR Tweaked Settings", here:

http://www.coolpix7900.com/VR_Tweak/7900VRTweak.htm


Possibly this tweak works for other Coolpix cameras and not only the 7900.
It should work for sure though for the 5900 too.


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Old Aug 12, 2006, 9:09 AM   #2
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The downside of your "tweak" is that your photos will be darker (underexposed), and if you brighten the photos using software, visible noise will be higher, just as if you used a higher ISO speed to begin with. You will also lose dynamic range with this technique.

What your tweak is doing is deliberately underexposing using Exposure Compensation, and that works with any camera with an Exposure Compensation setting, film or digital.

It can be useful when you run out of ISO speed options. For example, I've been known to deliberately underexpose ISO 3200 with my Konica Minolta 5D in order to get faster shutter speeds. That increases noise, but somtimes noise is preferrable to motion blur. In one of the low light restaurants in my area with a guitar player, I need to underexpose 1/3 stop at ISD 3200 to get my shutter speeds up to 1/10 second shooting with a 100mm f/2 wide open at f/2. I keep forgetting to ask them if they'd move a candle or two closer to the performer. lol

Just in case you're not familiar with it for it's intended purpose, Exposure Compensation lets you alter the way a camera's autoexposure/metering algorithms expose an image (brighten or darken it compared to the way the camera metered the scene). It's one of my most frequently used settings on most cameras.

A +EV value gives you a brighter exposure. The camera uses a slower shutter speed and/or larger aperture (smaller f/stop number) to get a brighter exposure, compared to what the camera's autoexposure/metering algorithms would have selected.

A -EV value gives you a darker exposure. The camera uses a faster shutter speed and/or smaller aperture (higher f/stop number) to get a darker exposure, compared to what the camera's autoexposure/metering algorithms would have selected.

If you're in Av Mode (Aperture Priority) and use Exposure Compensation, the camera will vary the shutter speed (since you're setting the aperture). If you're using Tv (Shutter Priority) mode and use Exposure Compensation, the camera will vary the Aperture (since you're controlling the shutter speed).

If you're in Auto (or other similar modes), the camera may vary aperture or shutter speed when you use Exposure Compensation. In low light, since your aperture is already wide open, it varies shutter speed if you use a -EV setting.

Correct Exposure comes down to the amount of light, the ISO speed, the shutter speed, and the aperture. A variety of combinations will produce identical exposure.

You use Exposure Compensation if you want a brighter or darker image compared to what the camera's metering would normally give you in the same conditions.

An example of when you may want to use a +EV setting is for a backlit subject, where the subject would normally be much darker than the rest of the image. Since the camera has a limited dynamic range, it doesn't know that you want the dark subject exposed properly (at the expense of the rest of the image). If you brighten the exposure for one part, the rest may be overexposed.

If your subject is much brighter than the rest of the image, you may want to use a -EV setting for Exposure Compensation so that your subject is not overexposed (making the rest of the image darker, too).

The camera has a limited range of bright to dark that it can capture. So, it makes choices so that most of the iimage is correctly exposed, depending on your metering mode. Sometimes that may not be what you want. That's where exposure compensation comes in.

Basically, your "tweak" is darkening an image compared to the way the camera would have normally exposed it (giving you underexposed images because of a faster shutter speed). If you run out of ISO speed choices, this can be a useful technique, if you're willing to put up with the increased noise after brightening the image so that it's exposed correctly later.

Underexposing ISO 200 by 2 stops (-2 EV setting), would be the equivalent of shooting at ISO 800 from a noise perspective after you brighten the image later to match the way the camera would have taken it to begin with. ;-) This is known as "push processing".

It's best to use the camera's ISO speed control first, unless it's already at the maximum setting, or you want to simulate an ISO speed "in between" available values. That's because you lose dynamic range by underexposing and pushing the image later with software so that it's as bright as it should be, compared to letting the camera amplify the signal from the sensor to begin with.

For more on how underexposing negatively impacts dynamic range, see this article:

http://www.luminous-landscape.com/tu...se-right.shtml

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Old Aug 12, 2006, 9:44 AM   #3
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JimC,

Thanks for the information. I know all these anyway.
But this is a compact point and shoot and not a Konica Minolta 5D.

If you don't have a tripod at night with you, there is no other way to take a handheld blurry-free shot without using flash with the 7900. Also not too many people who have a 7900 carry tripods with them at night. They use the camera mostly as a point and shoot and not for creative night photography.

If you don't use this tweak and try to take a nightshot without tripod and without flash, that most people will do, the 7900 will use a 2 second shutter speed, resulting in a totaly blurry image.

I don't claim that this is the best way to take a nightshot without a tripod, and I don't use this method with my more advanced cameras (even though that most of the times I underexpose my nightshots to avoid blown highlights) but for the 7900 that you cannot adjust the shutter speed and aperture this tweak is the only way to take the shot, handheld and without flash.

The images maybe underexposed but they still very much usuable and even if use software to brighten them up later they can still make excellent 4x6 or even 5x7 prints.

So it is much better to be able to take even an underexposed shot than to completely miss the shot.


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Old Aug 12, 2006, 9:47 AM   #4
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Yes.. as I mentioned, I've been known to deliberately underexpose myself.

I just wanted to make sure you (and others reading your article) are aware of what it's doing, since your article mentioned no downside.

The downside is darker images (you're deliberately underexposing) compared to the way the camera's metering would have taken the photo, and if you use software to brighten them, visible noise will be higher, just as if you used a higher ISO speed to begin with.

This is a common technique (deliberately underexposing using a -EV setting to get faster shutter speeds, and brigthening the images later). It's known as "push processing", and it's a useful technique with film, too.


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Old Aug 12, 2006, 10:02 AM   #5
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JimC,

This is just a tweak for the 7900 and possibly for other compact Coolpixes. And yes, it would work for other compact cameras of other manufacturers, that don't have an image stabilizer, but I don't know how well it will work because I think that only the Nikon compacts have "Spot AF Area" metering that yields brighter results than the "Spot" metering the rest of the compact cameras have.

Personally I use a tripod for nightshots, but there are times that I'm walking on the street or other occasions at night that I cannot possibly carry a tripod all the time, or it is not always convinient to pull out a tripod, or because I don't have time to set up a tripod, otherwise I will miss the shot.

So this tweak is for these special occasions I mentioned above plus for amateur people that don't know how to take a handheld blurry-free photo without a flash.

Yes, Im aware of the underexposing using this tweak, as I'm also aware that a handheld nightshot without a tripod and without a flash would yield a totaly blurry photo.

Thanks for commenting and replying.


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Old Aug 12, 2006, 10:09 AM   #6
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JimC,

Can you help me with this (since you are a moderator)?

When I created my account, I put my user name exactly how "Archangel" is spelled in my language (Greek). How can I change my user name from "Arxaggelos_GT" to "Archangel_GT" ?

It seems that I cannot change my user name. Can it be done from some of the website's moderator? I only want to change my username. The rest remains as is.

Can you help me with that?


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Old Aug 12, 2006, 10:17 AM   #7
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Arxaggelos_GT wrote:
Quote:
JimC,

This is just a tweak for the 7900 and possibly for other compact Coolpixes. And yes, it would work for other compact cameras of other manufacturers, that don't have an image stabilizer, but I don't know how well it will work because I think that only the Nikon compacts have "Spot AF Area" metering that yields brighter results than the "Spot" metering the rest of the compact cameras have.
It doesn't make any difference. You're making it harder than it needs to be. Simply use more or less Exposure Compensation for the desired results.

If you use a -1 EV setting, and the aperture is already wide open (as it will be in low light), a camera will underexpose 1 stop (shutter speeds twice as fast as the exposure algorithms would have normally selected for the metering mode you're using).

If you use a -2 EV setting, and the aperture is already wide open (as it will be in low light), the camera will underexpose 2 stops (shutter speeds 4 times as fast the exposure algoirthms would have normally selected for the metering mode you're using).

Settings in between can be used, also. Some cameras allow adjustment in 0.3 EV (1/3 stop) increments and some allow them in 0.5 EV (1/2 stop) increments

This works with any camera that has Exposure Compensation in it's Auto or Programmed Auto modes (or in Av Mode). ;-)

The exception would be if a camera has a slowest allowed shutter speed it would normally use, and the shot would already be underexposed to begin with (so, you wouldn't want to use as much negative Exposure Compensation anyway).

You can also accomplish the same thing using Manual Exposure for cameras that have it. Simply expose so that your meter shows the desired amount of underexposure by setting shutter speeds faster.

The downside is underexposed (darker) images, lower dynamic range, and increased visible noise when you brighten the images later to match the way the camera would have taken them to begin with.

Arxaggelos_GT wrote:
Quote:
It seems that I cannot change my user name. Can it be done from some of the website's moderator? I only want to change my username. The rest remains as is.
I'll look into it to see if there is a way to modify the name in the MySQL database (I have no built in user interface to do that).

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Old Aug 12, 2006, 1:50 PM   #8
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JimC,

It is not so easy as you imply. Just altering only the Exposure compansation is not enough to take low light handheld blurry-free photos without flash.

Probably other users can confirm what I'm saying, or if you have access to a 7900 yourself you can try it yourself. Specific combinations of specific parameters are needed to do the job correctly.

Altering only the Exposure compensation as you suggest is not enough, or at least not enough for the 7900.

Possibly it works as you say with other cameras, but not with the Coolpix 7900.
If it was so simple, I wouldn't call it a "VR Tweak".


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Old Aug 12, 2006, 1:54 PM   #9
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By metering from a brighter portion of the image, in effect, you're only using more exposure compensation. There are only 4 variables involved for exposure: Available Light, ISO Speed, Shutter Speed, Aperture). The only thing you're doing is using a faster shutter speed than you should for proper exposure.

The concept is very simple. All you are doing is underexposing the image compared to how the camera would normally expose it in order to get faster shutter speeds.

This concept has been around for ages, and it has it's downsides (underexposed/darker image, lower dynamic range, increased visible noise after processing for correct brightness).

It works with any camera with the ability to use Exposure Compensation, and even some cameras that don't (for example, some cheap film cameres may not have an exposure compensation feature, yet you can set the ISO speed to a higher value than the film you're actually using in it for the same effect).

Read any book on basic photography to understand how these variables (light, aperture, iso speed, shutter speed) relate to each other. Most good books on basic photography will also explain the concepts for metering and how to use exposure compensation to change the values the camera would normally use for aperture and/or shutter speed).

Your tweak is nothing more than deliberately underexposing to get a faster shutter speed. ;-)

There are pros and cons to this solution, and I just wanted to make sure that readers are aware of the cons (since your article did not mention them).


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Old Aug 12, 2006, 3:15 PM   #10
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P.S.

There is no "free lunch".

If you keep the shutter open too long for the light, aperture and ISO speed, you'll get overexposed images (brighter), resulting in loss of highlight detail.

If you don't keep the shutter open long enough for the light, aperture and ISO speed, you'll get underexposed (darker) images, resulting in loss of shadow detail, and increased visible noise if you try to brighten the images later (just as if you used a higher ISO speed to begin with, or even worse in some cases).

Yes, deliberately underexposing an image (which is exactly what your tweak is doing) is one way to get faster shutter speeds in low light. But, it has it's drawbacks.

Again, I use this technique, too from time to time (as do many photographers). I just wanted to make sure that readers are aware that it has it's downside, since your article currently says this:

" Some Bad Side Effects
Haven't seen any yet."

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