Friday, January 1, 2010

Hight ISO and low light

So I listened to a short tutorial the other day about low-light photography. The setting... indoors, no flash available, and not a ton of ambient light to work with... but slow moving subject -- an indoor wedding.

Now how do I make a great shot?   Well, use manual settings, that's for certain.  I want complete control.   I want to shoot manual ISO, manual exposure, manual white balance.  But keep it in auto focus, because you don't want to miss a thing.
1) the option is to lower my fstop to around 1.4-3.0. But the question is, "does my lens go that big"? Remember the lower the fstop number, the larger the aperture, and the more light that is hitting the sensor.  But I have to remember that the lower the fstop, the more shallow the depth of field (DOF). So if I am taking a shot of more than one person, don't fall below f4.0.  Generally speaking, I want everyone to be in focus in these ceremony shots.
2)  another option is the slow down my shutter speed. But I don't want to go too slow... 2 reasons... 1 is that my subject might be moving faster than my exposure and thus be blurry. The second reason is that I will get camera movement that also causes blurriness. A good rule of thumb with that is if I am shooting a relatively slow subject, try to keep my shutter speed around the same value as my depth.  If I am shooting with a 50mm lens, try and keep that shutter speed at 1/50th of a second. If I am shooting a moving subject, double that number (shoot faster) like 1/100th of a second with 50mm lens. Does that mean I need to go 1/600th of a second with your 300mm lens? Try it and see.
3) Finally, to the subject of the day... ISO.  I can increase my ISO. This was mentioned in an earlier post in minimal detail. The ISO essentially defines the quality or graininess of your image. The higher the ISO, the less light that is required to get the same exposure but the more grainy the image will be.
This is where an expensive camera body is enticing.  For instance, the D700 or D3 ($2500 up to $7000) camera bodies handle low lighting great because of their ability to use high ISO values and still look great.

So, I am hopefully going to be shooting an indoor wedding in May.  Last August I used two SB600 strobes (off-camera flashes) attached to the ceiling and pointed toward the ceiling. They were placed just above the action of the wedding, as seen in this image.

And get shots during the wedding, no matter where I was in the room, like these...
It was very convenient, and provided a consistent lighting for me.

But this next time I probably won't have the luxury of strobes in the room. So how do I get those same shots without the added light? So this led me to the high ISO question. Today I have been playing about with high ISO and different length lenses. I also downloaded some noise reducing software trials to see what performed better if I were to need these.

And the results... without using any noise reduction software...
If I maintained a good original exposure, I found that for my purposes*, ISO of 640-800 worked fine. But when I tried to add fill light or increase the exposure in post-processing, that's where I saw the degradation of the image.

Having said that, I would really like to try and print some of these high ISO images so that I can get a feel for how they look enlarged. That way I can get a feel for how large I can go on the print with what ISO. This is critical when thinking end product... if I just placing the image in a book as a 4x5 image, I should be fine. But what if I am enlarging to be a 2-page spread (22"x8") in the same book? Does is still maintain it's integrity?

So, what have I learned thus far with the high ISO? Make sure my light meter is in the slightly over-exposed region when shooting ISO (not blown out spots, but well exposed). And darker areas show the graininess more than lighter areas.

Stay tuned, I will hopefully be posting re: the orton effect next time.

Pick of the Day...
seen here

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