Bird lens

[Diminished29]

Ok, through some research and what not I have a question for all you bird shooters out there.

Does this math work out pretty well as far as focal length is concerned on birds:

*For every 10-20ft 100mm of focal length is needed depending on size to fill the frame*

Size for 10ft being small birds such as sparrows and redpolls and 20ft being for larger birds such as blue herons

So here goes:

I'm seeing a redpoll at about 40ft away, so I'm gonna need roughly 400mm to fill the frame with it?

I understand one can "crop" at 100% but, I'm wanting QUALITY so I'm wondering if my math is correct?

[PacAce]

I have birds out in my backyard, like house finches, goldfinches, etc, that are just close to or closer than 40ft from my back door where I have my camera and I can't get them to fill my frame with my 100-400 set to 400. Maybe if they were half the distance away they might. AAMOF, that's one of the reasons I moved one of the goldfinch feeders to within 15 to 20 ft. of my back door.

[Diminished29]

So, it sounds like from your estimation that I'd need 100mm for every 5ft to get a small bird to fill the viewfinder. Wow! Sigmonster here I come...guess I'll need some teleconverters too. Ok, just kidding, but wow, I thought 10ft per 100mm for a small bird to fill the frame was pretty bad, but 5ft!

I guess when I think about it though, to get what I'm trying to go for 10ft per 100mm may be alright, since it seems most people compose a branch or tree limb or something in the picture along with the smaller bird to give it character and show it in a more natural setting.

Again, I'm just one who likes to do my homework before spending lots of money. Looking to move on from the A610 in several months, but I'd like to have decent cost effective glass to go with my DSLR when I do start shooting with it.

[Diminished29]

This picture right here, is nothing special, but I took it the other day when I was testing calculations and whatnot.

Here is a redpoll and a sparrow at about 12ft. Its an 80% crop. With some USM at 75 sharpening and some saturation in Paintshop.

It was shot with my A610 at 29mm. So, what would that be the equal to on say a 300D or 20D?

[PacAce]

Originally Posted by Diminished29

This picture right here, is nothing special, but I took it the other day when I was testing calculations and whatnot.

Here is a redpoll and a sparrow at about 12ft. Its an 80% crop. With some USM at 75 sharpening and some saturation in Paintshop.

It was shot with my A610 at 29mm. So, what would that be the equal to on say a 300D or 20D?

[http://i42.photobucket.com/albums/e3...rowredpoll.jpg[/]

The lens on the A610 on the long end is equivalent to 224mm on the 300D and 20D.

BTW, the bird on the left is a house finch.

[In2Photos]

Try it out. Take a can of soda, roughly a little bigger than a small bird and set up a 100mm lens. Move the can until it fills the frame and record the length from which you placed the can. Then report back to us with your findings. Actually, I might try this at home today and see how it goes, now that I got my new tripod.

[gasrocks]

I teach a class on Wildbird Photography. Just to show my students I took a pix of a chickadee at 55 feet away w/ 1800mm (equiv.) and the bird fills about 1/3 the frame. Good enough to crop though. Upon further review..... more like 1/4 or 1/5th of the frame.

[In2Photos]

Originally Posted by In2Photos

Try it out. Take a can of soda, roughly a little bigger than a small bird and set up a 100mm lens. Move the can until it fills the frame and record the length from which you placed the can. Then report back to us with your findings. Actually, I might try this at home today and see how it goes, now that I got my new tripod.

OK, tried it out at lunch today. Here are the results. Only resized. Camera was on a tripod shooting down at an angle so the distance is really just horizontal distance, no vertical distance taken into consideration.

5 feet

_MG_3833.jpg

10 feet
_MG_3834.JPG

[In2Photos]

15 feet
_MG_3835.jpg

20 feet
_MG_3836.jpg

[In2Photos]

Size of bottle.

_MG_3837.jpg

[CyberDyneSystems]

Mike,. just to clarify,. you used a 100mm?
On a 1.6.. so were talking 160mm feild of view?

[In2Photos]

Originally Posted by CyberDyneSystems

Mike,. just to clarify,. you used a 100mm?
On a 1.6.. so were talking 160mm feild of view?

Correct, sorry, thought I read somewhere that the OP was looking at a 1.6x camera.

[CyberDyneSystems]

I think your right!.. I wasn't challenging your findings at all!

I just wanted to be sure we were all on the same page

To me the results show 5 feet per 100mm on a 1.6 crop body.
Now.. whos going to check a 300mm or longer to see if the the math holds up?

[In2Photos]

Originally Posted by CyberDyneSystems

I think your right!.. I wasn't challenging your findings at all!

I just wanted to be sure we were all on the same page

To me the results show 5 feet per 100mm on a 1.6 crop body.
Now.. whos going to check a 300mm or longer to see if the the math holds up?

No, no, you are fine. And I wish I had a 300 mm to test. Then maybe I wouldn't be cropping so much with my bird photography. Oh well, one thing at a time.

[cfcRebel]

Ah, that reminds me i need to refill my Men's Daily vitamin. About to run out.