How do I take photos of birds inside cages (as shown in the picture below) and have it appear that there is no cage at the front, which blocks the bird.
Taking photo of the bird inside the cage:
and the photo taken to have the following effect:
Assumption - Using a tele-lens of 300 mm (be it compact camera / DSLR)
Your example is made up of images from two different situations. It is extremely likely that no lens / camera on earth could achieve the sort of image shown in that situation without "cheating" by using some sort of processing - and probably multiple images - to deal with bar removal.
You CAN achieve extremely good results when you have control over where the camera is located relative to the bars. An object that is closer to the focal point than the focal length of the lens will be defocused and light from it's image that reaches the sensor will be dispersed over some or all of the rest of the image. This causes loss of contrast of the overall image but spreads or removes the image of the bars. The closer the bars are to the sensor plane and the further they are behind a plane one focal length in front of the focal point, the more they are dispersed.
So:
Camera lens front surface almost touching the bars if possible.
Long focal length
Large aperture to decrease depth of field.
Subject as close as reasonably possible.
Lens as close to the bars as is reasonably possible is perhaps the biggest "secret".
Through the bars: This was taken through cage bars the same as are seen in the cage above and at rear. The lens front is almost against the bars. Aperture f/1.8. 50 mm (APSC)
This Toucan was taken at f/6.3, 18mm (APSC)
There is very solid close spaced mesh between it and me.
This photo was taken through a heavy mesh as seen here .
See also my answer here
Experimenting to see what results you can get is useful.
You'll find you can optically "remove" even quite thick things (like a pencil) if very close to lens.
I you're going to be standing on the ground with cages on poles like in the image you posted then you're out of luck.
In order to throw the cage bars out of focus to the extent to which they don't show up in the image your lens will have to be very close to the cage (touching if possible). You'll need a wide aperture lens with a fairly close focusing distance.
Place the lens inside the cage. That is the simplest way.
Depending on the shooting distance, the thickness of the wire the cage is made of, and the maximum available aperture on your lens you can try the following:
If you are able to use a wide enough aperture and keep the bird in focus while the front of your lens is very close to the cage, the blur from the bars might become diffused enough to be minimally visible.
But the best way is to shoot the bird with nothing between your lens and it.
In general, these are the factors of blurring out the bars:
You can calculate the impact of different settings here..
If the image above is your real-life situation, this will be very very difficult. Why? Chances are that bird in the cage will be so far away that the depth of field on the distance will not be able to blur out the cage bars sufficiently to make them disappear 100%. Your only hope is that the wire on the cages is very thin and that you get a better angle to shoot (=closer up) as well as the bird sitting ideally on the other end of the cage.
Why? The bird has to be possibly far away from the cage to have the DOF make it disappear. The cage is far away, your zoom lens has limited aperture and the angle to the cage forces you to move far away. All 3 factors lower your chances.
Here is an example with a couple of generous assumptions:
Let's assume the cage is 20 cm in diameter. Also, the cages are about at 6 meters height. Let's also assume that you will have ideal conditions to use a F/4 aperture. But how far will you have to be away from the cage? Well to even look into the cage and see the bird on the other side, you will have to see it from almost straight ahead. Let's be again positive and assume a 27 degree angle from the bottom would work. That means you have to have twice the distance on the ground than the cage is high = 12 meters. Assuming the bird is not blocked by the bottom of the cage. The DOF then would be still 24cm - 4 cm of DOF, which is not enough to make the bars disappear completely, since the bird will most likely sit in the center of the cage. With a 24 cm depth of field, your whole cage will be in focus - all bars included. If you need to move further away, the problem becomes worse. Same if there is not enough light or your shutter speed (300mm needs a certain speed to not blur from shake, and the bird might be moving) needs to be too high to get the bird sharp.
Use a camera with a lens that's small enough to not be obscured by the bars.
The camera on your cell phone will certainly work. Some point and shoot cameras may have small enough lenses too.
Place the camera against the cage with the lens positioned between bars and shoot.
To shoot that photo with a larger camera, like a DSLR, you're going to have to open the cage door, or get a cage with invisible bars (very hard to find).
