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Old Feb 12, 2003, 9:02 PM   #1
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Default D-100 and strobes

Like I said I am looking to buy a Nikon D-100 I have a Quantum radio Slave and Dyna lite UNI 400jr Strobes with rackrabbit battery. Can i expect good results with this camera. I shoot cutting horses mostly in not so well lit arenas also looking for recomendation on a lens Im shooting from 50 to 100 feet away. Thankyou
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Old Feb 12, 2003, 9:20 PM   #2
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cowboy43

I don't have a real answer, but I can make a comment or two (and ask a related question.)

50-100 feet away is fairly far, but at least you are taking pictures of a large subject. You might want fast lenses, depending on how fast the horses are going to be moving. I'd guess a 80-200 would do (since the subject is so large), but I don't have first hand experience. Going to a larger tele will start to raise the price a lot, since you might need a fast lens in that dark arena.

A friend of mine uses a flash slave system with his D100 and is happy with it. I don't know the make/model, though. He masks the onboard flash, and uses it to just trigger the main flashs.

My question is if there is any standard chart which contains this type of info:
A Item of size X will fill 2/3's of the vertical view at distance Y with a Zmm lens.

Where:
X = some standard size object (a 1' tall pole?)
Y = some distance (i.e. the info I'm looking for.)
Z = each reasonable tele length (200, 300, 400, 500, 600mm)

I'm sure someone with a better understanding of optics could calculate this... but that person isn't me! Something like this would answer part of cowboy43's question (and it would answer my question about what distance each telephoto lens is good for, for a certain size object.. in my case birds.)

Eric
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Old Feb 12, 2003, 9:26 PM   #3
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If this helps im looking at spending $1000 to $1500 on the lens
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Old Feb 12, 2003, 11:51 PM   #4
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Quote:
Originally Posted by eric s

My question is if there is any standard chart which contains this type of info:
A Item of size X will fill 2/3's of the vertical view at distance Y with a Zmm lens.

Where:
X = some standard size object (a 1' tall pole?)
Y = some distance (i.e. the info I'm looking for.)
Z = each reasonable tele length (200, 300, 400, 500, 600mm)

Eric,

To answer the question, I will simplify the camera lens system down to a single convex lens , which diopter varies depending on actual zoom setting ( diopter = 1 / focal length in meter)
The optic center of this imaginary lens is not easy to determine exactly because of the complex optical multiple lenses arrangement of the camera zoom lens . Nevertheless , this should give you enough accuracy for choosing a necessary focal length value.

Consider this “figure”


|
|
X
|
|--------------------------------Y---------------------------(OC)--------Z--------|
.................................................. .................................................. ...............H
.................................................. .................................................. ................|

(I use the dots characters just to place the H at the right place)


Where:
X = height of the object
Y = distance of the subject to the optic center of the single convex lens
OC = optic center of the single convex lens
Z = focal length of the single convex lens ( the actual camera zoom setting)
H = height of the object's image
( X and H can be symmetrical referring to the horizontal optical axis as well , this is just the usual academic representation , also illustrate that the image is upside down compared to the real object)

When the image is “in focus” , we have the relation:
X/Y = H/Z

Let’s use metric system:
Z = actual focal value , in mm , film camera equivalent
X, Y and H in mm
I assume that the height of captured picture is equivalent to 24 mm ( 35 mm film capture area is 24 mm x 36 mm )

Example 1:
I want to fill the height of the my camera capture area with a 1 meter height object , at a distance of 5 meters , what should be the focal of the zoom setting ?
X=1 meter = 1000 mm
Y=5 meters = 5000 mm
Then Z = H x ( Y / X ) = 24 x ( 5000 / 1000 ) = 120 mm
ie: the zoom should be set around 120 mm ( 35 mm film camera equivalent)
(You notice that the optical center of this imaginary single lens is 120 mm from the imaginary 24 x 36 film plane)

Example 2:
You want to fill 2/3's of the vertical view of the image of a 300 mm pole ( 1 foot) at distance of 1 meter , what should be the zoom setting?
X= 1 foot =300 mm
Y=1 meter = 1000 mm
H= 24 mm x 2/3 = 16 mm
Then Z = H x ( Y / X ) = 16 x ( 1000 / 300 ) = 53 mm ( approx)

Depending on your exact need , you can make out a chart with a spreadsheet program ( Microsoft excel , or Lotus 123 as in the old DOS time )

Hope that this help
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Old Feb 13, 2003, 7:10 PM   #5
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Thnkyou very much this helps a bunch. very well explaned
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Old Feb 13, 2003, 11:32 PM   #6
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KCam,

Thanks a lot. That formula is simpler than I thought it would be. Lets see, if I did this right.....

For cowboy43, with a 5' tall horse (no rider), that would mean he could get away with a 85mm prime and get it to 2/3 frame at around... 40 feet. That is a little further than I'd like. At 50mm it would only be 24 feet a away. Not bad. A good f/1.4D lens is $270 at adorama. That would handle the low light very well. (I've read that the f/1.8 is as good a lens, FWIW, and $150USD cheaper.)

Nikon doesn't make a 50mm IF, which is a pitty. You might not want the reflections off the equipment. The 85mm f/1.4 has IF, but its over $1,000. Doesn't sound worth it. And the low power zooms with IF are expensive as well.
------------
Thanks again for that equation. Very handy. Unfortunately, it's telling me that I'm more likely to get the shots I want by digiscoping. Sigh. Less flexable than a D100, but I can't afford both. Hard decision time.

Eric
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Old Feb 14, 2003, 1:09 AM   #7
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Eric,
Hard decision , yeah, that's why I got only a D7i with a 28-200 mmm @ 2.8-3.5

PS: in the 100 feet range, you could also consider a good flash gun ?
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Old Feb 14, 2003, 9:23 AM   #8
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KCan

Ya, the D7i is a very nice camera. I considered it and a CP5700. Both have nice long reaching glass. But a 200mm will make a 1' object 2/3 in a D100's frame (< 35mm) at about 19'. That would work for taking some nature photography, but not work very well when I'm using it while birding. The subjects will be smaller and further.

That is a rather appealing f-stop, though. I didn't realize that it was that good.

I assume the flash gun suggestion is to lower the required f-stop, and therefor drop the price of the lens? Do they really have a 100' range? That is an interesting idea.

Eric
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Old Feb 14, 2003, 11:51 AM   #9
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Quote:
Originally Posted by eric s
KCan

I assume the flash gun suggestion is to lower the required f-stop, and therefor drop the price of the lens? Do they really have a 100' range? That is an interesting idea.

Eric
Eric,
Yeah, with flash , you can afford to use a smaller F, a higher speed.
100' range flash is not rare.
Just for example, the Metx 45 series can deliver 45 meters GN (~~ 130 feet) at 35 mm focal coverage and ISO100.
Put an apropriate telephoto adapter and you double it's range.

http://www.stevesforums.com/phpBB2/v...t=3630&start=0
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