Samsung HMX-H100 video cam

Let's do some tinkering with Maple to see how high the HMX-H100 Samsung Video Camera can zoom optically.

The camera has a side-ways working Zoom switch, whose range is n=23 clicks. To determine the true range of the zoom, we need to photograph a distant image and apply the zoom to see how it affects the initial image. For this, we photograph a distant light source, using all zoom switches and we get a list of photos.

We now extract the dimensions of the photos in pixels using Photoshop. For each normally sized^{[1]} cam photo above:

- Select the Magic-wand tool.
- Click inside the street lamp (white area) to determine the full extent of the street lamp.
- Select "Copy".
- Select "New..." to read the dimensions of the copied object in horizontal and vertical pixels.

After the above has been done for all photos, we remove all duplicates and we get a list of dimensions (x,y), which we input on Maple:

> restart;

> with(plots):

> PL:=[[17,11],[17,12],[17,12],[20,11],[22,13],[24,14],
[26,13],[30,15],[35,17],[40,19],[47,21],[62,27],
[83,33],[103,41],[122,47],[158,58],[208,78],[231,84],
[253,92],[271,98],[338,120],[356,128],[430,156]]:

For an optical instrument and an object subtending an angle è_{0} under magnification 1X and è under magnification MX, the magnification M is defined as:

The situation is depicted in the following diagram.

Magnification for optical instrument: M=DE/DF

From the list of pixel sizes PL, we determine the average magnification with Maple:

> M:=array(1..nops(PL),[]);

> for n from 1 to nops(PL) do

> M[n]:=evalf(abs(PL[n,1]/PL[1,1]+PL[n,2]/PL[1,2])/2);

> od:

The luminaire lies at a distance of AB~30m, and has a size BC~35cm, therefore at magnification 1X, it subtends an angle è_{0}, such that tan(è_{0})=BC/AB. With Maple,

theta0:=evalf(solve(tan(x)=0.35/30,x));#actual object angle @M=1.

Next, let us determine the angles the object subtends to, under different magnifications:

> theta:=array(1..nops(PL),[]);

> for n from 1 to nops(PL) do

> theta[n]:=solve(M[n]=tan(x)/tan(theta0),x);

> od;

Because the angles are small, tan(è_{n})/tan(è_{0})~è_{n}/è_{0}, so let's verify that we got the correct magnifications for all switches n\in {1,2,...,23}, using both calculations:

> for n from 1 to nops(PL) do

> print(n,evalf(theta[n]/theta0),evalf(tan(theta[n])/tan(theta0)));

> od;

1, 1.000000000, 1.000000000

2, 1.045450136, 1.045454545

3, 1.045450136, 1.045454545

4, 1.088226198, 1.088235295

5, 1.237938006, 1.237967914

6, 1.342197180, 1.342245989

7, 1.355563460, 1.355614973

8, 1.564068485, 1.564171123

9, 1.801955312, 1.802139037

10, 2.039814383, 2.040106952

11, 2.336425632, 2.336898395

12, 3.049653178, 3.050802139

13, 3.938581196, 3.941176471

14, 4.887965156, 4.893048128

15, 5.716369443, 5.724598930

16, 7.266297789, 7.283422460

17, 9.622909978, 9.663101612

18, 10.55904667, 10.61229947

19, 11.55305416, 11.62299465

20, 12.33974328, 12.42513369

21, 15.23397941, 15.39572193

22, 16.09756070, 16.28877006

23, 19.40066154, 19.73796791

If we instead used only lateral magnification^{[2]}, we'd get:

> for n from 1 to nops(PL) do

> print(n,M[n]);

> od:

1, 1.

2, 1.

3, 1.

4, 1.176470588

5, 1.294117647

6, 1.411764706

7, 1.529411765

8, 1.764705882

9, 2.058823529

10, 2.352941176

11, 2.764705882

12, 3.647058824

13, 4.882352941

14, 6.058823529

15, 7.176470588

16, 9.294117647

17, 12.23529412

18, 13.58823529

19, 14.88235294

20, 15.94117647

21, 19.88235294

22, 20.94117647

23, 25.29411765

__Conclusions__

For optical magnifications, the camera has n=23 zoom switches with maximum magnification achieved being M~24X on (x) (lateral), and maximum average magnification M~19.7X on (x,y) (lateral/longitudal)^{[3]}.

- The images on the table above have been reduced to 25% to save bandwidth. When measuring dimensions, one has to use the original-sized images.
- For lateral only magnification (x), we should recalculate with > M[n]:=evalf(abs(PL[n,1]/PL[1,1])); in the first Maple code loop.
- The camera can actually go higher, if one engages its Intelli-Zoom
*digital*magnification. For this case, a similar measurement should be performed.