globetrekker Loc: Bend, OR

OK, learning time for me. I had assumed long exposure necessitates small aperture, which means decreased DOF. But I never remember to factor in working distance. I guess I'm just not sure how. But I'm at a loss to understand how f/32 could ever provide deeper DOF than f/22. At what point does working distance negate the normal rule that smaller aperture produces narrower DOF?

mcveed Loc: Kelowna, British Columbia (between trips)

The length of the exposure has nothing to do with depth of field. DOF, for a specific camera, is dependent on three factors: aperture, distance from subject and focal length of lens. Smaller aperture means increased DOF not decreased. At a given focal length and distance from subject, the smaller the aperture (i.e. the larger the f-number: f8 is a smaller aperture than f2.8)the greater the depth of field. One should speak of a shallower or deeper DOF, not a narrower DOF.

mcveed Loc: Kelowna, British Columbia (between trips)

Beautiful light and interesting subject. I can see the effects of diffraction quite clearly on this image. None of the edges are crisp - they all seem to have a visible glow or haze around them. It is not the same as being out of focus or motion blur. It has a distinctive look a bit like looking through a thin haze, but only when you look at the edges of things. I would be interested to know how far the lens was from the subject when you took this.

P.S. I wonder if Dave was viewing this on his iPad??

Nightski

Very close ... probably just a couple of feet. If I remember right .. it was a few months ago.

Nightski

I was pretty close, if I remember right. But it doesn't matter. I like to play with my lenses at all the apertures to see what happens. This day I felt like F/32. :-) I think it was because I wanted to get a bunch of them in focus ... which was a composition mistake.

mcveed Loc: Kelowna, British Columbia (between trips)

If you have an iPhone, there are a number of free Depth of Field calculator apps that you can download. That way you always have one handy. It can be a great aid until the relationship becomes instinctive.

globetrekker Loc: Bend, OR

Thanks. Knew most of that. Including that smaller aperture produces greater DOF. Dohhh! Brain took a vacation when I wrote that, I guess.

I do think that length of exposure has an indirect effect though, because a long exposure, e.g., in this example, necessitates a larger aperture in order to have a mathematically correct exposure. There's room for creativity and overruling the sensor, of course, but in general, the linkage exists.

Nightski

I have one right on the main page of my cell phone. I do use it .. sometimes. But sometimes it's so cold I just can't get my hands out of my gloves to do another thing. I did get it out the other day. I was shooting a river scene. I wanted the foreground cattails to be in focus. They were about thirty feet away. I wanted infinity focus. I remembered John Greengo saying that an easy way to cheat is to figure out how far your subject is, and double that distance and focus there. So then I thought ... well are the cattails my subject? No .. not really, but I do want them in focus. The whole scene was my subject. I wasn't sure ... but I did get the whole thing amazingly tack sharp. I focused on the cattails and hoped for the best. LOL

This day that I was taking this shot, it was rainy on and off, I had to battle down several branches to make a clear shot to the shrooms, and the mosquitoes were about eating me alive. I should have dug out my cell ... but I just guessed. I do look at the online DOF chart frequently though, and try to make mental notes of focal lengths and distances. You are right ... it will take me a long time to get it right without having to look it up.

R.G. Loc: Scotland

I went back for a closer look, and the stuff just beyond the "horizon" is starting to go out of focus, so the DOF was just deep enough to include everything up to the horizon. So maybe f/32 was necessary after all. Although you could have decided to not include as much foreground and focussed a bit farther away, which would have allowed you to stop down. I would agree that the foreground is too extensive and mostly not adding interest.

mcveed Loc: Kelowna, British Columbia (between trips)

A linkage definitely exists between aperture and shutter speed, but you have it backwards. A longer exposure necessitates a smaller aperture, not a larger one. And that is only assuming that the ISO remains unchanged. As far as exposure is concerned there is a three way linkage with aperture, shutter speed and ISO. As far as DOF is concerned shutter speed is not, itself, a factor.

Nightski

Three things to consider when determining Depth of Field.

1)Focal length - How long is the lens you are using?

2)F/Stop - The smaller your aperture the greater DOF you will have. Apertures above F/16 cause diffraction. A softness that is due to the way the light comes through the smaller opening in the aperture.

3)Distance from subject - The closer you are to a subject the less DOF you will have.

globetrekker Loc: Bend, OR

Jeeez, I knew that too. I need to stop typing faster than my brain can think. :lol:

Nightski

Yes, I agree with every thing you have said. I spent lots of time this summer playing with these mini landscapes. I learned so much doing it. It's much easier to control than a grand landscape. I'm excited for next year's mushroom season. :-)