Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Reply
 
Thread Tools Search this Thread
Old Oct 18, 2005, 12:31 AM   #1
Senior Member
 
kenmck15's Avatar
 
Join Date: Aug 2005
Posts: 2,568
Default

I have looked at some demo photos from some cams and have noticed a significant increase in the noise levels when using iso400.

Why would u actually use such an iso setting over the likes of say exp conpensation???

What benefits does iso400 offer over iso100 in a bright scene. I think i have been told that high iso levels are better for low light but i have seen on steves sample images from the h1 with iso 400 are very noisey??
kenmck15 is offline   Reply With Quote
Sponsored Links
Old Oct 18, 2005, 2:32 AM   #2
Senior Member
 
Join Date: Jan 2004
Posts: 824
Default

kenmck15 wrote:
Quote:
I have looked at some demo photos from some cams and have noticed a significant increase in the noise levels when using iso400.

Why would u actually use such an iso setting over the likes of say exp conpensation???

What benefits does iso400 offer over iso100 in a bright scene. I think i have been told that high iso levels are better for low light but i have seen on steves sample images from the h1 with iso 400 are very noisey??
In general (unless trying for a special grainy effect), most people select the lowest ISO they can use under the lighting and movement conditions. Exposure compensation may work to an extent, but once you reach the lowest (brightest) f-stop on your lens, your shutter speeds start increasing (getting longer), and unless you have very bright conditions the chances of camera shake increase. The benefits of using ISO 400, 800, 1600, 3200 or higher are that you can keep up fast shutter speeds under darker conditions. That's not important when shooting a still life from a tripod, but if you're shooting moving objects (sports, etc.), it is very important.
So to answer the question about the bright scene, you might want to raise the ISO if the subject was a car race and you couldn't get a fast-enough shutter speed to a) stop the car's motion and/or 2) to keep from having camera shake with a long telephoto lens. And you're right, noise/grain increases with higher ISOs. That's the compromise involved.


Norm in Fujino is offline   Reply With Quote
Old Oct 18, 2005, 5:09 AM   #3
Senior Member
 
kenmck15's Avatar
 
Join Date: Aug 2005
Posts: 2,568
Default

thank you for the replay

i understand wheere you are coming from

thanks
kenmck15 is offline   Reply With Quote
Old Oct 18, 2005, 9:39 AM   #4
Senior Member
 
Join Date: Dec 2002
Posts: 5,803
Default

I have a slightly different take on this. I only shoot at ISO200 on my 20D, unless the shutter speed is staggeringly high.

For me, the quality of ISO200 is so good, that I would rather have the extra shutter speed than the marginal inprovement in noise. But I rarely shoot at ISO400 because the noise is too much. Yes, I can use noise reduction software to remove noise... and on some images this works very well. But most of the time I would rather use exposure comp to get the shutter speed and fix it later. But I shoot wild animals most of the time, so I need that shutter speed.

The danger of using exposure comp (to me) is two fold. First, you forget its set. Of course, this applies to ISO as well. The second is that, while you can bring out details from the darks, it isn't the same as a properly exposed shot in the first place. There are some opinions that digital sensors have more detail in the light areas than the dark. That to get the absolute best quality you should shoot as close to over exposed as you can. I don't completely buy this, but I haven't experimented with this myself.

Eric
eric s is offline   Reply With Quote
Old Oct 18, 2005, 10:19 AM   #5
Senior Member
 
Freefly's Avatar
 
Join Date: Jan 2004
Posts: 368
Default

I really donĀ“t like to use high ISO but sometimes you just have no choice.

At a recent wedding I had oneEOS 20Don a tripod set up highin the Organ/choirarea for long exposure, low ISO shots, and I was running around downstairs with a 1D MKII, 16-35 F2.8L, 70-200 IS 2.8L and no flash.

The church was so dark with minimal flash allowed, I had to use ISO 640, hand held, no flash 40th/sec F3.2 on the first shot below and 60th/sec F2.8 hand held with ISO 800 on the second.

I actually ended up with quite a few nice images and although they needed "some" help with Neat Image, I was generally chuffed to bits with the results. The lack of detail in some faces is due to a "soft" filter in PS that lightens the image some more.

It is sooo nice to be able to change ISO "mid shoot" whereas with film you had to change rolls mid shoot or change camera...happy digitaldays!

Nick
Attached Images
 
Freefly is offline   Reply With Quote
Old Oct 18, 2005, 10:20 AM   #6
Senior Member
 
Freefly's Avatar
 
Join Date: Jan 2004
Posts: 368
Default

...
Attached Images
 
Freefly is offline   Reply With Quote
Old Oct 18, 2005, 1:54 PM   #7
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

kenmck15 wrote:
Quote:
I have looked at some demo photos from some cams and have noticed a significant increase in the noise levels when using iso400.
Noise may actually be worse than you see in some of thesample photos, too. I noticed that some of the samples are outside at faster shutter speeds,and well exposed (samples from the H1 you mentioned). ;-)

If you have a scene with a lot of difference in bright and dark areas, some parts are going to be underexposed compared to others (you may see even more noise, depending on the colors and how well noise shows up in them). For example, some skin tones seem to be bad aboutnoiseshowing up with many cameras at higher ISO speeds.

Fortunately, there are some pretty good tools to help clean it up now. If you want to see how well some do, download some of the sample images and run them through some of the modern tools like Neat Image or Noiseware (and you can download free or demo versions of both to try out).

Quote:
Why would u actually use such an iso setting over the likes of say exp conpensation???
Well... let's make sure you understand how they differ.

ISO speeds are not designed to lighten or darken an image. How an image looks from an exposure perspective (light or dark), should not change with ISO speed using a camera's autoexposure (withsome exceptions, like flash photos where you are trying to increase the amount of ambient light in the image by using higher ISO speeds when shooting a closer subject, since many cameras will choose a specific shutter speed/aperture for all flash photos).

If you use a higher ISO speed, the camera can use faster shutter speeds (or smaller apertures) for any given lighting condition. If you use lower ISO speeds, the camera can use slower shutter speeds (or larger apertures) for any given lighting condition.

The most common reason to use higher ISO speeds is to get faster shutter speeds to help prevent blur (from either subject movement or camera shake).

For example, at ISO 100 and f/2.8 for a scene properly exposed at 1/30 second, you could use ISO 200 and f/2.8 for the same scene and get the same exposure at 1/60 second. So, each time you double the ISO speed, the camera can use shutter speeds twice as fast for the same lighting condition and aperture.

Exposure Compensation is used for a different reason, with different results.

If you want a brighter photo than the camera's autoexposurewould normally give you (for example, if you have a backlit subject in shadows that is much darker than the rest of the scene), you use a +EV setting. Then, the camera will use slower shutter speeds and/or alarger aperture (smaller f/stop number)to expose the scene brighter.

If you want a darker photo than the camera's autoexposure would normally give you,use a -EV setting with Exposure Compensation. Then, the camera will usefaster shutter speeds and/or asmaller aperture to expose the scene darker.

Due to Dynamic Range limitations (ability of the camera to properly expose both brighter and darker areasin some images), you sometimes need to tell it what you prefer to be properly exposed.

Exposure Compensation is one way to vary it's normal exposure behavior, making a scene brighter or darker so the parts you are more interested in are properly exposed (sometimes at the expense of other areas in a high dynamic range scene).

ISO speed is not designed to do this (vary brightness of an image fromhow the Camera's autoexposure would normally expose it).

But, you can use Exposure Compensation in a similar way as increasing ISO speed.

For example, in lower light, with your ISO speed set to ISO 200, if shutter speeds were at 1/30 second at the camera's widest aperture (for example, f/2.8 with many models), you could set Exposure Compensation to -0.5 EV to deliberately underexpose the scene 1/2 stop. Then, the Autoexposure system on most models would choose a shutter speed 50% faster if the lens was already at it's largest Aperture Setting (or if you were choosing a specific Aperture via Av Mode).

That's one way to get faster shutter speeds (deliberately underexpose using Exposure Compensation). But, noise levels increase that way, too (just as if you'd used a higher ISO speed to begin with, after you brighten the image back up again later with software).

I sometimes do this to simulate ISO speeds "in between" available settings.


JimC is offline   Reply With Quote
Old Oct 19, 2005, 12:30 AM   #8
Member
 
Geeek204's Avatar
 
Join Date: Jun 2005
Posts: 72
Default

eric s wrote:
Quote:
I have a slightly different take on this. I only shoot at ISO200 on my 20D, unless the shutter speed is staggeringly high.

For me, the quality of ISO200 is so good, that I would rather have the extra shutter speed than the marginal inprovement in noise. But I rarely shoot at ISO400 because the noise is too much. Yes, I can use noise reduction software to remove noise... and on some images this works very well. But most of the time I would rather use exposure comp to get the shutter speed and fix it later. But I shoot wild animals most of the time, so I need that shutter speed.
I have some imput also, most photographers are concerened with getting the best "quality" of the image. And they underexpose and overexpose things so they don't blow out the highlights, etc. and then they just fix it in their photo editor. Most people don't realize that every time you modify that image in photoshop, you loose a lot of midrange tones and detail. Every notch that you move it, there is a decline in quality. I try and get the best picture I can off of the camera, not in Photoshop. Even if it takes a little bit longer and I have to take more pictures, what do I care? I use digital and can delete anything.

Storm
Geeek204 is offline   Reply With Quote
Old Oct 19, 2005, 4:35 AM   #9
Senior Member
 
kenmck15's Avatar
 
Join Date: Aug 2005
Posts: 2,568
Default

thanks for all the response guys, much better udnerstanding now
kenmck15 is offline   Reply With Quote
Old Oct 29, 2005, 12:41 AM   #10
Senior Member
 
toshi43's Avatar
 
Join Date: Oct 2005
Location: Vernon BC Canada
Posts: 1,618
Default

If you can use high ISO settings withoutnoticeable noise, why wouldn't you? Some of the new Fuji cameras have anextremely highISO range that's actually very usable. I've taken indoor shots with the flash off and ISO set to 800 and there was less noise than my previous Canon A75 had at ISO 200. Damned amazing, if you ask me.
toshi43 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:43 AM.