Lens length (Zoom setting) picking tips

Now, first comment. This tip has nothing to do with that irritating "zoom zoom" boy in the commercials, rather this has to do with the Zoom and lens capabilities on your camera.

I'm driving along, my camera is in the bag beside me, but I only have the 80-400mm lens on it. I see a wonderful sunset - do I stop and try to take the picture or should I just enjoy the sunset and not take the picture?

I'm driving along, my camera bag is beside me, I see a badger running parallel to the vehicle - can the lens on my camera take a good picture or should I just enjoy watching the animal?

I see a coyote sitting in front of me, my camera has a 50mm lens on it (I'm taking a close up shot of some flowers), I have other lenses in my bag - which lens do I put on to take the picture? I'll be lucky to get one chance, let alone a second.

I am taking a large group family picture, where do I have to stand to get them all in - or do they have to move closer together no matter where I stand.

All of these and more have happened to me. Years ago I would have to get out the camera, make a best guess, look through the lens, try different lenses or zoom settings until I can decide. One day however while driving, I realized there was a better way. I realized that, since each zoom length gives a specific angle and since my arm is not growing anymore, if I held it out - I could fairly accurately guage what each zoom would include in a picture. Then I could see a) what lens would be best and b) whether it was worth even trying to take the picture with the lens(es) I have with me.

The chart I created for myself is below. I have memorized the values for 28mm, 50mm, 200mm, 400mm and 800mm. The way it works is this. I took my camera lenses, and look through them. I lined them up on the left side with something, I then looked at how far to the right I could see, I picked something on the right as my marker. I then held out my hand and arm it various configurations until I had a combination that worked with my body. Mine may be good starting points for you, but most of you will find out that, because you are different sized you will have to fill in the "Rule of thumb" column with your own values.

In my case, I only calculated the "long" distance. Most cameras, and all 35mm cameras have film that is longer in one dimension that the other. If you shoot 35mm film, a 4x6 should in theory be the same length & width as the film (a 8x12 also matchs, but an 8x10 is too short in the long dimension, you lose an inch off each end.)

Now, when you want to take a picture, you hold out body parts to measure the picture to choose the lens. For example, in my case with the badger, when I held out my arm, the badger was less than half the width of my pinky and the background was bland, I only had a 400mm lens, so the badger was going to be less than 1/4 of the picture. If I wanted a "I really saw a badger" snapshot, I could have taken the picture, but if I wanted a good quality image for display, I was better off just enjoying the badger and hope for a better close up another day. I enjoyed watching the badger for several minutes. With the coyotee, it appeared that, with the background, that an image the width of my fist would give an attractive shot. I put my 80-400 on and took the picture at 200. I was also going to try for a closeup using the lens at 400mm, but he was gone before I had a chance.

I find this method to be much quicker than lifting a camera up to my face and checking, and when trying to take pictures of people acting naturally, I find I can often "yawn and stretch", to take my measurement without catching anyone's attention, then, putting the correct lens on, or adjusting the zoom to the correct length, I can raise the camera and take the picture before anyone starts "acting" for the camera.

		---------- Field of View @ ----------
mm	View	10'	25'	50'	100'	Rule of thumb.
8	180.0º	Infinite	Infinite	Infinite	Infinite	Any fisheye, ie 15mm fisheye, will also have 180 degrees - they draw a circle of 180 degrees.
14	114.2º	20.44
17	104.0º	18.6	46.5	93.1	186.1
24	84.1º	15.0
28	75.0º	13.4	33.6	67.1	134.2	Hand in a fist. Width of outside of elbow to end of fist.
35	63.4º	11.3	28.4	56.7	113.5
50	46.8º	8.4	20.9	41.9	83.7	Sick out both thumbs, hands in a fist. Width of 8 fingers & both stuck out thumbs.
70	34.3º	6.1	15.2	30.4	60.8
80	30.0º:	5.4	13.4	26.8	53.7	Width from tip of pinky to tip of thumb when spread as far as I can and held out at arms length
85	28.5º	5.1	12.8	25.5	51.0
100	24º	4.3	10.8	21.5	43.0
105	23.3º
135	18.2º	3.2	8.0	16.0	32.0	Width of 4 fingers plus thumb sticking out partly
200	12.3º	2.2	5.5	11.0	22.0	Width of fist (not thumb) when held out at arms length
300	8.25º	1.5	3.8	7.5	15.0	Width of 3 fingers when held out at arms length
400	6.15º	1.1	2.8	5.5	11.0	Width of 2 fingers when held out at arms length
500	5.0º	0.9	2.3	4.5	9.0	Width of 1.75 fingers when held out at arms length
600	4.1º	0.7	1.8	3.7	7.4	Width of 1.5 fingers when held out at arms length
800	3.1º	0.6	1.4	2.8	5.6	Width of 1 finger (not pinky) when held out at arms length
1000	2.5º	0.5	1.1	2.3	4.5	Almost width of pinky when held out at arms length