Friday, June 24, 2011

ISO, fstop, EV from a different perspective

more light please...

there are lots of entries/articles out there explaining fstop, ISO, shutter speed, and the like. They all are speaking from the camera's perspective. Well, today I want to allude to these from the photographers perspective.

The scenario... My boy is in the dining room having breakfast, alone. The rest of the kids are asleep or otherwise occupied.  I grab the camera for some shots because the light from the window (no other ambient light source) is inviting.

I am using the 70-200mm lens... because it's attached and I really like it for portraits.  I try to compose the shot with mainly his face and his breakfast.  I also want to get some darks just behind his head because I want his exposed face to really stand out. I want to contrast with focus as well, hence the long zoom and wide aperture (more to come).

And mind you, I am not thinking all of the following items prior to first shot. I am thinking, shooting, looking at image, then repeating the process until I start to see what I want... often called "chimping".

First, I put the camera in A mode (aperture priority)- this way I can adjust the fstop, the ISO, and the EV. So ISO first. I have recently set my ISO to full stops... This means when I move my ISO selector, it moves in these increments 100, 200, 400, 800, 1600. If I had a cropped sensor, I would be a little more conservative and put 1/2 steps. This is because the full size sensor looks just fine at ISO 1600. So, ISO 800 is what I choose... [could have gone 1600 in retrospect to allow for faster shutter speed, because about half of my images weren't crisp clear.]  By the way, I have also changed my fstop to full stops too.  This is because when I am working with my Manual powered flashes, it's simpler math.  So ISO 800

Next, fstop. When I adjust fstop in A mode, I am wanting to see what the camera gives my in shutter speed. So I choose f2.8 (wide open). This will give me a really narrow depth of focus, but I may be willing to take it. I try 2.8 and I try 4. I end up using 4 because it gives me a little more playing room of focus distance. See previous blog of depth of field, or depth of focus  If I chose f2.8,  point my camera at my subject, then it gives a shutter speed of 1/125 - that's ok. But I want deeper focus, so I change to f4 and figure the 1/60 will work out.

I end up shooting my subject at 160mm so that my subject more fully fills the frame.
***The rule of thumb to avoid blur due to large zoom is to have the shutter speed match the zoom. So my shutter speed should be around 1/160***   Having said that, vibration reduction allows me to use slower speeds and not get the blur.

So, I've set my ISO to 800 and my fstop to 4.  I turn on the VR (vibration reduction) - don't use this if you are on a tripod.  I shoot off a couple of shots, and my subject is too bright for my taste.  What can I do to underexpose the picture a little, yet not have to change to manual mode and dial in f4 and 1/60th?  The answer:  adjust the EV.  Exposure value (EV) is a nice little tool.  I find I use it when my camera is trying to expose for the darker part of the image, and my subject is overexposed.  This usually occurs when the majority of the frame is dark and I am using matrix metering.
IE:  yesterday I was scouting out a place for some engagement shots I am doing for a neighbor and I had a barn in the semi-shade and the cloudy/blue sky as well.  It appeared that I was overexposing the sky to get the barn in correct exposure.  So I dialed my EV down 1 full stop (to -1.0) and those highlights were no longer blown out.  I can easily go back and add highlights in post-processing.

To recap... ISO 800 due to low lighting
f4 to maintain large aperture but still have good depth of focus
EV -1.0 to allow a slightly underexposed image
Result:  good lighting, not so good composition.

What did the subject think of the image?  --"I am really small... I have volcano hair."
Analysis... my subject is smack in the middle... fix: crop
Also, I am not liking the blue chair in the background... it is distracting.  fix: bw or desaturate just the blue
if bw, then increase the contrast to pop the whites

So, the blue chair becomes gray and is still distracting... bummer.  But I like the image other than that.

Pic of the day:  I really like this pose and composition... in fact most all of her images are impeccable.

Sunday, June 19, 2011

off-camera flash

I have been using off camera flash for sometime... I have been using Nikon's commander mode which allows me to fire my off-camera flash using my camera.  A nifty system, but has some shortfalls:
1) you have to have an on-camera flash to trigger the off camera flash - the problem is when you don't want an on-camera flash to be firing.  Sure you can set it down to it's lowest setting, but you are still introducing a front light source. 
2) you have to make sure the infrared receiver on the off-camera flash is 'visible' to the on-camera flash.  This limits your range and makes using that flash more complicated and less reliable.

So, I was at my cousins wedding and her photographer was using the Cactus Triggers, which are one of the least expensive triggers on the market.  I had read about these, but had heard mixed reviews on their reliability.  But this photographer had nothing but good to say about them. 

I looked more into them and they had some problems with one of the versions (v4).  Now they have the v5's.  So I ordered a pair and have been trying them out.  

Overall, I really like them.  This is not a review of these wireless triggers per se, so I won't elaborate too much.  Briefly:  they work on manual setting, so you don't get to use Nikon's TTL technology (which is basically Auto Flash mode).  They are very reliable thus far.  And I love not having to line up the old infra-red sensors.  The only problem I have found thus far is that they didn't work with my SB-600 flashes until I put some duct tape covering one of the pins on the bottom of the SB-600s.  Thanks forums for pointing me that direction.
The newer triggers are nice because they claim to work up to 1/1000 shutter speed. They worked at 1/500 for me, but not so well at 1/1000. Further testing may reveal otherwise.

One more shot:   settings:  70mm ISO 800 f4, 1/125 -off-camera flash powered at 1/128 M (SB800)

By the way, here was my set-up for this shot.

And don't worry, the goblet is empty.

Pic of the Day:  

Picture came from the photographer, Amanda, who was so kind to entertain my questions regarding the cactus triggers...  I think she really nails this shot:  great evening light with equally subdued pose and colors; great contrast with her depth of focus, and superb lines/curves take me through the whole of the subjects.  I don't think she uses any reflectors, diffusers, or fill flash... just good natural lighting.

Wednesday, June 1, 2011

Portrait time

Due to excessive rain, I have been taking pictures of the kids indoors the past couple of weeks.  What are some things you can do to get enough light indoors?

First of all, beware of the mixed lighting sources.
Note that the fluorescent lights put off a greenish hue, the tungsten lights a bluish hue, and outdoor is the standard here.  And it's all about balance.
If you have a subject close to a really bright window, the fluorescent light in the room may not even show up in your image. Another way is to introduce a flash. This allows you to shoot with the window light and the flash (which are quite similar in their white balance) in a room with tungsten or fluorescent.   So here's the lighting setup for these portrait shots.
The flash on the floor is set at the lowest setting it has M 1/128.  So is the camera flash.  The camera flash is used here to simply trigger the SB600 flash.  The exposure is f3.2 at 1/80 at ISO 800.  
I chose 1/80 because I notice if I use 1/60 or slower, my kids pictures are blurred due to subject movement.
I like: the focus at f3.2 and 70mm (enough of the subject is in focus).  To calculate my depth of field... it was taken with  Nikon D700 taken at 5ft away from subject at f3.2.  That gives me about 4 inches of depth... that's not a lot... so I really need to ensure that my focus point is the eyes.  
The lighting: I like that my subject is a little brighter than the background.  
I don't like: the highlight on his face is a little hot and a little larger than I wanted.
Do over:  I would move the flash back a little bit more... maybe more of 1 or 2 o'clock (instead of the 2:30 it is currently at)
And hope I don't lose you here... I would dial my f-stop up just a bit, maybe to 4.5 so that my lowest setting on my flash wasn't as strong.  More on flash output power*** later
Here are some others from the same shoot:

Pic of the day:

*** flash output is influenced by distance to subject, flash power setting, f-stop and ISO of camera.