Depth of field

[Naym]

In his guide gocny says

• 2. Shoot from relatively far away with a relatively long lens. For photographing bonsai, I get good results using a 70mm lens on my D70 digital SLR; this is the equivalent of using a 120 mm lens (short telephoto) on a regular 35 mm camera.

Is this also the equivalent of of moving the camera back and zooming in a little when using a digital camera with no manual aperture control, an auto focus and optical zoom?

Having the whole tree in focus is still something I am struggling with on trees with a lot of depth. I've tried all sorts of distances (between camera and subject) with and without zoom and it seems to be completely the luck of the draw at the moment. I'm begging to wonder if it's simply that and auto focus camera can not detect the distance to the subject properly when the subject is so small (relatively). I would go back to my old 'fancy' camera but it's film and so negates the usual reason I take pictures of my trees.

[luan]

Yes, it is the same, but it won't make your photos any clearer.

I think he has chosen the 120mm as it is often considered best for portraits, and I guess it is the same for bonsai. At this length the perspective is pleasing. With a shorter lens you need to move in closer to get a good size, and this will warp the perspective. Longer lens will compress the picture too much. The background blur should also be pleasing at 120mm.

It is surprising that you are having depth of field problems with your point and shoot, because they usually have a large depth of field.

Can you turn autofocus off and use spot focus?

[stymie]

When using an automatic camera, the aperture is made smaller in better light thus increasing the depth of focus. The answer may be to shoot in a brighter environment.

[schmik]

This is a hard subject as you have no manual control over your camera.

In general I can get away with F5.6 using a 70mm and F8 using a 40mm. Bigger trees have required me to go as far as F11.
As mentioned above, light is your likely problem. The camera see a low light situation and uses and open apperture. Try more light and also try putting the camera in landscape mode to force a larger DOF.

If you want to get more knowledgeable about the problem then get the free software 'photome' or 'exiftool'.
These tools pull out the photo info from the JPG... like shutter, iso, apperture and hundreds of other values.

Have a look at the pics and at least confirm that that the apperture is the issue. Then try to devise a way of fooling the camera.... or a get a 2nd hand DSLR.

mike

[schmik]

First pic is 40mm at F/8, 2nd is 70mm at F/11.

40mm.jpg

70mm.jpg

Both have the whole plant within DOF but check out the background. 70mm shot, you can't see the wrinkles in the backdrop and it has 'blacked out' nicely. 40mm shot has more open aperture so the background should be blurred out more but it isn't. Focal length is why. DOF is very different at different focal length / distance to subject.

Have a look at:
http://www.dofmaster.com/dofjs.html

mike

[Naym]

Thanks for you thoughts guys I'll keep persisting and try all your tips.

Luan: I'm not sure what you mean by "spot focus" but I am unable to alter the focus setting on the camera.

Stymie: I'll have another go in a bright environment, I always found that this gave bad colour and glare, but I guess I can correct some of that post-hoc.

[BGM1971]

Hi
A lot of compact digital camera's have a portrait function built into them. Without knowing the camera, I can only guess.
This will give you a good medium DOF.
Have a look through your camera's manual to see if you have this.
Hope this helps

Brad

[Naym]

One suggestion to use the landscape setting and another to use the portrait setting.

I've tried both and so far after minor post-hoc editing there is no difference. I suspect I just need to play around more with the distances, essentially measuring the depth of field of the camera under the conditions that I photograph my trees.

[Sime76]

Nayam,

I would go with using the Landscape setting - as that will always try to set the aperture for a wide DOF, where portrait will try to do the opposite to make the background go out of focus so the portrait will stand out.

Also DOF is always shorter when zoomed in as opposed to zoomed out.

An idea would be to compare the meta data (in particular the aperture ) on a shot where you used portrait and one where you used Landscape.Just right click on the file in windows and select properties.