Which ISO setting do you use for UW?

[Warren_L]

I routinely shoot between 200 to 400 ISO, as visibility and ambient light in the water where we dive locally around here tends not to be great. Haven't really noticed much degradation in quality. If I were lucky enough to be able to dive frequently in clear water, then I too would be shooting 100 all the time, but unfortunately that is not so.

 

[HowardE]

ISO 100. I've never needed more than that in the majority of my shooting. I try and shoot my lenses at the point where they will be sharpest for long DOF shots which is generally around F16-F20, and for open aperatures, I probably wouldn't need the extra light anyway. The only time I'll go up is if I'm in a really really low light WA situation like a cave. Regarding your images, a fairer assesment would be a print of the images at a reasonable size. Most of my prints are A4 (umm..this is something close to legal paper) and A3 (this is double A4 or double legal, approx) at minimum and I wouldn't want to deal with the noise that *I* personally do notice.

I was going to test the printing of two photos between the ISO 100 and 200 as the true litmus test. For posting online, I would seriously doubt that any real difference would be seen.

 

[Diver Dennis]

You're right about posting online howarde. Not much difference in a 150kb image.

 

[alcina]

When I first got my 20D I somehow set it to 400. The Canon seems to handle it well - of course, they were exposed properly in the first place and that always helps.

UW I shoot 100 almost all the time. I have started playing with higher ISOs but not enough to make any decisions. As with all things photo - any time you gain in one place, you lose in another. So it's a matter of using the tool correctly.

 

[Diver Dennis]

I agree alcina. Why not work with the best possible all around setting? In thinking about it, I can use ISO100 for everything I've been doing so far so why switch? I'll experiment a bit though.

 

[Darnold9999]

Thought I would do a search re this. From this article and others like it I take that you really are not changing the sensitivity of the CCD device - you are boosting the signal. If I understand this correctly (and I doubt that I am ) you would be wise to shoot at the native sensitivity of your sensor and post process to get the image you want.

Anybody explain this better and why I would want to vary ISO to something other than the sensitivity of the sensor? Is the amplification within the camera prior to digitizing better than doing the amplification during post processing?

From Digital Photo Pro Mag http://www.digitalphotopro.com/articles/2006/mayjune/isospeeds.php

ISO speed.
Image sensors have an innate “native” sensitivity, generally in the ISO 100 to 200 range. When you set a higher ISO speed, amplifiers in the image sensor’s circuitry increase the gain before sending the image data to the A/D converter to be digitized. The sensor’s sensitivity doesn’t actually increase; the camera is just amplifying the data it produces. In the process, image noise is also increased, making the image “grainier”—sort of like what happens when you “push” film speed. But generally, digital SLRs produce better image quality at higher ISOs than film, especially pushed films.

If you set a lower ISO speed than the sensor’s native sensitivity, the camera’s image processor adjusts the image data after the A/D converter converts it to digital form. In the process, the dynamic range is reduced. So it’s best to shoot at the sensor’s native ISO whenever

 

[HowardE]

you would be wise to shoot at the native sensitivity of your sensor and post process to get the image you want.

You can't change DOF in photoshop.

 

[SuPrBuGmAn]

ISO doesn't change the DOF either.

A properly exposed shot with a higher ISO will have less noise than a 'pushed' low ISO shot. Pushing exposure too much in post processing will pull grain out in the image as well. Areas overexposed or underexposed too much will not carry any detail information for post processing to work with...

Another words, if you can't properly expose a shot(or get close) at low ISO and any useable shutterspeed and aperture; you'll want to raise the ISO to retain detail - even if it costs a bit of noise.

 

[f3nikon]

ISO doesn't change the DOF either.
Another words, if you can't properly expose a shot(or get close) at low ISO and any useable shutterspeed and aperture; you'll want to raise the ISO to retain detail - even if it costs a bit of noise.

Yes I agree for above water shooting or without a strobe, but when shooting U/W you would most likely be using a strobe "thingy", so you will have more than enough light to properly expose an image even at the lowest "true" ISO settings. Remember the rule about shooting U/W...get real close (2 feet or less) all strobes have more than enough power for this range even at the lowest ISO settings.

In fact at this range you are more likely going to over expose the image if your aperture is not near closed. So why waste the image to noise if you really don't have to. Shoot with the lowest "true" ISO setting possible.

 

[f3nikon]

Thought I would do a search re this. From this article and others like it I take that you really are not changing the sensitivity of the CCD device - you are boosting the signal. If I understand this correctly (and I doubt that I am ) you would be wise to shoot at the native sensitivity of your sensor and post process to get the image you want.

Anybody explain this better and why I would want to vary ISO to something other than the sensitivity of the sensor? Is the amplification within the camera prior to digitizing better than doing the amplification during post processing?

From Digital Photo Pro Mag http://www.digitalphotopro.com/articles/2006/mayjune/isospeeds.php

ISO speed.
Image sensors have an innate “native” sensitivity, generally in the ISO 100 to 200 range. When you set a higher ISO speed, amplifiers in the image sensor’s circuitry increase the gain before sending the image data to the A/D converter to be digitized. The sensor’s sensitivity doesn’t actually increase; the camera is just amplifying the data it produces. In the process, image noise is also increased, making the image “grainier”—sort of like what happens when you “push” film speed. But generally, digital SLRs produce better image quality at higher ISOs than film, especially pushed films.

If you set a lower ISO speed than the sensor’s native sensitivity, the camera’s image processor adjusts the image data after the A/D converter converts it to digital form. In the process, the dynamic range is reduced. So it’s best to shoot at the sensor’s native ISO whenever

Thanks for the link:

"If you set a lower ISO speed than the sensor’s native sensitivity, the camera’s image processor adjusts the image data after the A/D converter converts it to digital form. In the process, the dynamic range is reduced. So it’s best to shoot at the sensor’s native ISO whenever possible."

I was in on a thread all about ISO settings a while back, I just cannot seem to find it...just found it.

http://www.scubaboard.com/showthread.php?t=144362&page=2