Starting to understand.. maybe not

**perry** · 05-20-2007, 06:31 PM

I'm trying to figure out depth of field and how it is affected by focal length and aperture.

Here I have two similar pictures.. one with the foreground flowers in focus, one with the background. Fnumber and exposure time are the same according to the EXIF data. I think I may have cropped and resized one, and just resized the other. I forget now.

f/3.5, 1/640sec, 42.8mm focal length

f/3.5, 1/640sec, 42.8mm focal length

Trying to understand how the Fnumber plays in to things. If I had raised the number up to f/8.0, then the foreground and background would have probably been in focus no matter which I let the AF lock on to? Am I starting to understand this?

Now, let me try to throw focal length in to the equation. For my newbie mind, less zoom = shorter focal length? So, unzoomed with f/3.5 I'll have more in focus than zoomed in with f/3.5? Am I starting to understand the depth of field, or have I confused myself? I took a bunch of pictures today and have looked at them while paying attention to the numbers from the EXIF data, and I'm looking at an article on depth of field . Trying to figure this out but I think I'm just giving myself a headache.

**farace** · 05-20-2007, 06:44 PM

In a way, I think depth of field was easier to deal with on an SLR, because you could look down at the markings on the lens and see just what range would be in focus for a particular f-stop. I haven't seen anything like that on our digital. I can't say anything about the focal length, but in general, the larger number the f-stop, the smaller the aperature, and the greater the depth of field, but the trade-off is a longer exposure time.

**ouch** · 05-20-2007, 07:42 PM

Basically, you're correct. In general, wider angle lenses provide greater depth of field. I used to laugh at the autofocusing 20mm lenses- they would hardly move at all when focusing.

If you're using your camera manually, just remember that for each stop you open the lens, you have to cut the shutter speed in half to maintain the same level of exposure. The confusion sets in because most cameras are calibrated in 1/3 stops. For example, f/3.5 is 2 1/3 stops faster than f/8, and the shutter would have to be adjusted accordingly. With the new digital cameras, I fear folks just aren't going to bother to learn how photography really works, as the camera does all the work for you.

**icemncmth** · 05-21-2007, 12:51 PM

Originally Posted by farace

In a way, I think depth of field was easier to deal with on an SLR, because you could look down at the markings on the lens and see just what range would be in focus for a particular f-stop. I haven't seen anything like that on our digital. I can't say anything about the focal length, but in general, the larger number the f-stop, the smaller the aperature, and the greater the depth of field, but the trade-off is a longer exposure time.

And the old SLR's had a preview button that would show you what your pic woul d look like...

I grew up using and 8x10 box camera...It was great because it really gave you a feeling of what was going on in the camera..

I know digital is getting better but I doubt anytime soon you will get results like you did when you did a contact sheet in B/W with an 8x10 negative..

Really tought you how to dodge and burn...

**ouch** · 05-21-2007, 01:30 PM

When I let my daughter fire off a hundred shots and they look like crap, she says, "Who cares? It doesn't cost anything."

When you have to pay for film and developing, you have no choice but to learn from your mistakes.

**Klint** · 05-22-2007, 07:33 AM

I enjoy the benefits of my digital cameras. I can take pictures in a variety of ways and try out new techniques without breaking the bank. I have both a 35mm slr and digital slr and between the two, the film camera stays in the bag. I don't have to pay for my mistakes or my experimentation. I learn from my mistakes because I enjoy photography. If I didn't enjoy it, I'd simply not do it, film or otherwise.

**Dennis** · 05-22-2007, 08:15 AM

I think it is going to be a bit difficult for you to learn on a digital camera. The settings (aperture/F-stop & shutter speed) were the same so the difference was in where the camera auto-focused. If you really want to learn DOF and aperture settings, get a hold of a manual 35 mm film camera. They are dirt cheap (since everyone is selling them to buy digital).

On manual cameras, there is a preview depth of field button next to the lens. The approximate distances/ranges that will be in focus are also printed directly on the lens as well. You can stop the lens down to F8, look through the viewfinder and hit the preview button. This will close the aperture down to the setting (F8 in this case) and you can actually see what will be in focus and what is blurred. Off to the side in the viewfinder will be the light meter which (in the case of Nikons) was a swing arm over a range with green in the middle and red on each end. Adjusting the shutter speed swings the arm. These cameras also have exposure "correction" which digitals have where you can bump the exposure by 1/3 stops up or down to fine tune.

You can learn how this stuff works on a digital, but you are going to have to get the manual out and seriously dig into the controls on your camera. I find them to be not at all intuitive in many regards for the less expensive (sub $500) digitals, but they can be completely manually controlled. As you get into the (much) more expensive digitals, they emulate the feel and east of an SLR much better IMO.

Dennis
(Nikon F3 manual SLR, FTW!)

**Haiku** · 05-23-2007, 01:08 PM

Originally Posted by perry

I'm trying to figure out depth of field and how it is affected by focal length and aperture.

Here I have two similar pictures.. one with the foreground flowers in focus, one with the background. Fnumber and exposure time are the same according to the EXIF data. I think I may have cropped and resized one, and just resized the other. I forget now

Trying to understand how the Fnumber plays in to things. If I had raised the number up to f/8.0, then the foreground and background would have probably been in focus no matter which I let the AF lock on to? Am I starting to understand this?

Now, let me try to throw focal length in to the equation. For my newbie mind, less zoom = shorter focal length? So, unzoomed with f/3.5 I'll have more in focus than zoomed in with f/3.5? Am I starting to understand the depth of field, or have I confused myself? I took a bunch of pictures today and have looked at them while paying attention to the numbers from the EXIF data, and I'm looking at an article on depth of field . Trying to figure this out but I think I'm just giving myself a headache.

Yes, you are starting to understand this. The article to which you've provided a link is accurate.

At f8 both the foreground and the background would be in greater focus. If you dial in the minimum aperture, ie. f16 or f22, then there is a greater chance that you would have the entire thing in focus. And it would not matter what your automatic focus mechanism actually focussed on.

Here's a trick: Aperture markings are best thought of as fractions; and so "2" is 1/2 which is actually larger than "16" which is 1/16. The higher the number the smaller the aperture. The smaller the aperture the greater the depth of field.

The difficulty that you will have is the difficulty that others have pointed out: digital automatic everything cameras are at the end of the day not user friendly at all. The information that you need to make artistic decisions about your pictures is often very difficult to find in the menus, it is difficult to access and use.

The old mechanical cameras are just great: you turned the dial on the lens for the aperture and you turned a dial (generally) on the top of the camera for the shutter speed. You then pushed a button for a depth of field preview and you can actually see exactly what the depth of field looks like.

The old cameras - in particular the old manual film cameras give one complete control over the image because of the ease with which one can adjust both aperture and shutter speeds to make artistic decisions.

When the manufacturers started making "user friendly" cameras they started to go out of their way to hide the controls and the necessary information.

They made things even more difficult by having rather strange numbers for shutter speeds and apertures. Today's high end digital cameras can use any number at all for either aperture or shutter speed. This is not only completely unnecessary and very confusing and difficult.

The older cameras for example would start with shutter speeds of say one second and each faster speed was exactly twice as fast as the one before it (without getting too technical there is a jump in two places where that's not completely accurate but no matter for the sake of this argument). Apertures worked exactly the same way: each "stop" lets in exactly one half the light as the one before it. If you keep in mind that the factor is always the square root of 2, ie. 1.4, you will see that if you have a lens that starts at f1.4 the next f stop will be 2 then 2.8 then 4 then 5.6 and so on.

When you get in to the funny numbers that digital cameras use, then the arithmatic becomes a pain.

The real point here is that the old style cameras are dead easy to use when you understand how to use them.

But to answer your question: yes, you are beginning to understand it.

**Haiku** · 05-23-2007, 01:17 PM

Originally Posted by ouch

When I let my daughter fire off a hundred shots and they look like crap, she says, "Who cares? It doesn't cost anything."

When you have to pay for film and developing, you have no choice but to learn from your mistakes.

And so instead of her learning how to see, and perhaps to see artistically, and instead of learning how to think, she has learned that she has to count on technology and that she should not care if what she produces is garbage. Of course she does not have to care: it isn't her responsibility if the camera didnt' get a good picture. And if she takes a good picture once in a while, it is a matter of luck and not a matter of anything that she did or did not do. Her loss includes the loss of ever being able to take pride in an artistic accomplishment.

There is a cost by the way: the capital cost of the equipment is far far greater than the cost of buying and processing film. But one has to learn how to use film cameras to make them worthwhile. The total cost of all my film equipment is so small compared to an equivalent digital kit, that I can shoot a roll of film every 2 week for the next 10 years before my costs equal the cost of an equivalent digital camera. And at the end of the day, I have all the pictures printed on archival quality paper. If people who own digital equipment print the pictures as well, the costs never come out to be the same. And of course I am not counting the cost of computers, software or printers, I'm just counting on the cost of the camera and the lenses.

If I process the film myself and print it in a darkroom my costs spiral downward to the point where it is negligible for me to take a photograph.

There is also the hidden cost of never learning how to see and how to think.

**letterk** · 05-23-2007, 01:23 PM

Originally Posted by Dennis02

I think it is going to be a bit difficult for you to learn on a digital camera. The settings (aperture/F-stop & shutter speed) were the same so the difference was in where the camera auto-focused. If you really want to learn DOF and aperture settings, get a hold of a manual 35 mm film camera. They are dirt cheap (since everyone is selling them to buy digital).

On manual cameras, there is a preview depth of field button next to the lens. The approximate distances/ranges that will be in focus are also printed directly on the lens as well. You can stop the lens down to F8, look through the viewfinder and hit the preview button. This will close the aperture down to the setting (F8 in this case) and you can actually see what will be in focus and what is blurred. Off to the side in the viewfinder will be the light meter which (in the case of Nikons) was a swing arm over a range with green in the middle and red on each end. Adjusting the shutter speed swings the arm. These cameras also have exposure "correction" which digitals have where you can bump the exposure by 1/3 stops up or down to fine tune.

You can learn how this stuff works on a digital, but you are going to have to get the manual out and seriously dig into the controls on your camera. I find them to be not at all intuitive in many regards for the less expensive (sub $500) digitals, but they can be completely manually controlled. As you get into the (much) more expensive digitals, they emulate the feel and east of an SLR much better IMO.

Dennis
(Nikon F3 manual SLR, FTW!)

Actually, many DSLR cameras have a DOF preview button.

**Haiku** · 05-23-2007, 01:27 PM

Originally Posted by letterk

Actually, many DSLR cameras have a DOF preview button.

I stand corrected. I'm glad that they do, without DOF preview I wouldn't be able to create half the photos that I do. If I ever have to move to a digital, which may eventually happen, I now know I'll be able to get DOF preview.