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Newbie - blurring and aperture

fulcrum.1995 said:
Bringing down the aperture number will compensate for fast shutter speeds.
There is also exposure compensation that the camera should have options for
exposure compensation will most likely show a bar with numbers from -5 to 5 with little increments that will brighten and darken your image
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Ah, nevermind, it was because I wasn't using flash. With flash the picture is fine. Must be the room.

Very happy with camera now :D
 
run-kmc said:
Move the 50mm lens in close enough to capture the same image as the 500mm from far away, and depth of field is the same, everything else being equal. Aperture and focal distance are the only two things that affect depth of field. The only two things. The only two things. :D
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But by moving the 50mm lens to capture the same image (not really possible as different focal lengths will always give different perspective, no matter where you position them) you've changed the subject distance, and everything else is not equal anymore. A third variable A third variable A third variable ;)

In reality the mathematics of DoF is rather complicated, especially for physical camera lenses consisting of several elements. Most common equations are approximations. For large subject distances (subject distance greater than focal length) you get the "classic" DoF equation, which does depend on three things, Aperture, subject distance, and focal length. For closeup photography (subject distance roughly equal to focal length) an approximation can be used which makes the DoF depend primarily on image magnification and aperture, and in which the effect of focal length is minimal.

http://en.wikipedia.org/wiki/Depth_of_field#DOF_formulas
 
I am assuming you are trying to get results like these? You want something with smooth, nice bokeh (background blurred out)? These were taken with a 100mm macro and a 30D body. I took these about a year or more ago.
 

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These were shot wide open at 2.8, exposure on the white cat was 1/100.
The grey cat was taken at 1/250. Shot wide open as well.
 
Grasher said:
Incidentally, if anyone knows what this insect actually is I'd love to know. The shot was taken in the Grampian Mountains in Victoria, Australia. The insect was about 2-3 inches long.
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It's a cicada. They are common in many parts of the world. They make a sort of rhythmic scratching noise, especially when it is warm and humid out, that I always associate with hot August nights.
 
3 examples

All 3 of these shot handheld with a Nikon D700 and 105mm macro lens:

3968876646_58f2c10667_b.jpg

f/3 ISO 200 1/100


3968102911_905cd857a4_b.jpg

f/11 ISO 1600 1/60


3968103465_94868abcd6_b.jpg

f/32 ISO 6400 1/30

Notice the much shallower depth of field in the first shot at f/3. Basically only the stem is in focus. At f/11 the entire leaf and its reflection is (mostly) in focus but the foreground is still out of focus. By f/32 much more of the foreground and background is in focus, but the aperture is so small that it creates other problems for a handheld shot (slow shutter speed and high ISO which increase both noise and a loss of sharpness due to camera shake). In hindsight I should have taken a shot at f/4 and maybe f/5.6. Would have been interesting to see the tradeoff between depth of field and subject sharpness at those apertures.

I may shoot a series comparing the depth of fields of a DSLR and point-and-shoot (which will actually address the question the OP posed). Point-and-shoots have much smaller sensors than DSLRs, which means that for an equivalent field of view their focal lengths are much, much smaller. Depth of field varies by actual focal length, not by equivalent focal length. So when shooting with a point-and-shoot it's like you are always using an ultra (or even ultra-ultra) wide-angle lens with regards to depth of field. Even at fast apertures, it's often not possible to have a shallow enough depth of field to really isolate a subject with a point-and-shoot. That's one of the reasons why people put up with the added bulk, weight, and cost of DSLRs and fast lenses. On the other hand if your creative intent requires a large depth of field to keep everything in focus, a good point-and-shoot is actually better than a DSLR (assuming you are handholding and don't require the better image quality that a good DSLR/lens combo can offer).
 
I just ordered a new point-and-shoot (for those times I don't feel like dealing with the bulk of a DSLR). Once it arrives I'll shoot a series comparing it to my Nikon DSLR, specifically looking to answer the question of the OP. From a creative standpoint, what are the differences between a point-and-shoot and a DSLR? Are there images that can only be created with one format vs the other? Are DSLRs always better?

I may post my results here or I may create a new thread. Depends on the results of my experimenting.....
 
rhomsy said:
You should use this online calculator.

http://www.dofmaster.com/dofjs.html

It will calculate your depth of field for you.
Click to expand...


While DOF calculators are nifty, they don't necessarily help you understand what is actually going on. Additionally they are even less useful when the particular camera you are shooting with isn't listed (this is the case for me with the site you linked). When learning the basics of photography, I think it's sometimes helpful to actually experiment a bit to see first-hand how it all relates. Ideally you do this yourself by shooting test series where you play with the variables yourself. Barring that, it can be helpful to see the results of other's shooting test series (especially when it involves gear that you may not personally own). Just my personal take on it.
 
Well I did the comparison and decided to make a new thread with the results here.

Hope this helps with your original question OP :)
 
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