Noob Pics Questions (sorry...).

[v22TTC]

Yeah, I didn't explain myself very well. I'm saying that the camera will be on a tripod and using remote control or timer. I'll have the ISO right down (64 being the lowest I've seen) and everything on manual with the flash off, and good lighting etc.

So these cameras I'm looking at can have like 10-12 sec exposure times, so I should be able to close the aperture right down for depth of field, so I'll want the maximum f no. possible. What is the lowest maximum f no. I'll need for this kind of work?

EDIT: As in I need a camera that has a maximum f value of at least this?

Edited April 17, 2008 by v22TTC
Clarification.

[goblyn13]

this will explain it better than i can:

http://www.uscoles.com/fstop.htm

Shutter Speeds

Shutter speeds are a bit easier to understand, so I'll start with those. Both exposure controls run through a sequence of settings which involve doubling and halving the amount of light reaching the film. Shutter speeds are measured in seconds and fractions of a second and so the doubling and halving is self-evident. One quarter second is half as long as one-half second but is twice as long as one-eighth. One second is twice as long as half a second and half as long as 2 seconds. It's pretty easy, and this works through the whole sequence of shutter speeds. On my Nikon FE, for instance, the shutter speed sequence is:

8 seconds 4 seconds 2 seconds 1 second 1/2 second 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000

Each of these settings is clearly half/double the length of time of its immediate neighbours (OK, I know, 1/15 isn't exactly half the time of 1/8th and 1/125th isn't half the time of 1/60th, but it's close). This doubling/halving is thus pretty simple to comprehend for this exposure setting.

F/Stops

f/stops are a bit more confusing because the numbers appear so arbitrary. This is the standard sequence of f/stops from f/1.4 to f/22. Although it doesn't seem intuitive at first, in this sequence the f/1.4 setting lets in the most light while the f/22 setting lets in the least. Also, each of these f/stops has precisely the same halving/doubling relationship as the shutter speed sequence.

1.4 2.0 2.8 4 5.6 8 11 16 22

On the face of it, going from f/4 to f/5.6 doesn't sound like halving the amount of light. What's more, 5.6 is a larger number and sounds like it ought to be more light, not less. Neither does f/4 to f/2.8 sound like doubling the amount of light. In fact, each of the numbers in this sequence is a halving/doubling of the amount of light from its immediate neighbours, just like the shutter speed settings are. Not only that, but it makes sense, as I shall show below.

The reason that both the halving and doubling and the smaller numbers mean more light things make sense is that the f/stop is a ratio. The ratio is between the diameter of the aperture in the lens and the focal length of the lens. The focal length is generally measured in millimeters, so we'll stick with those as our unit of measure. On a 50mm lens, f/2 is saying that the diameter of the aperture is 25mm. The ratio is this 50/25 = 2. A good question might be, what is the area of that aperture? Well, the aperture is usually a set of five to fifteen blades which form a roughly circular hole, so we'll use the formula for the area of a circle, which as you all remember from fifth grade math is π * radius2. For π I'll use 3.14159265. On our 50mm lens, the aperture at f/2 has a diameter of 25mm which is a radius of 12.5mm. The area of the aperture is thus π X 12.52, or 3.14159265 X 156.25, or 490.9 square millimetres.

This fact by itself isn't all that useful. It is useful in relation to the adjacent f/stops. What is the area of the aperture at f/2.8? Well, because the f/stop is a ratio of the focal length to diameter, our 50mm lens at f/2.8 would have a diameter of 50/2.8 = 17.86mm. The area of the circle thus formed would be π X (17.86/2)2, or 250.5 square mm. That's about 250 sq. mm at f/2.8 and 500 at f/2, a double/half relationship. Aha! So that's it! The area of the hole doubles and halves, it's just represented by a ratio on the lens! No wonder it's so darn confusing.

Here's a table of the aperture areas for the common f/stops for a 50mm lens:

f/stop Diameter of

aperture (mm) Radius of

aperture (mm) Area of

Aperture (sq. mm) f/1.0 50.0 25.0 1,963 f/1.4 35.7 17.9 1,002 f/2.0 25.0 12.5 491 f/2.8 17.9 8.9 250 f/4 12.5 6.3 123 f/5.6 8.9 4.5 63 f/8 6.3 3.1 31 f/11 4.5 2.3 16 f/16 3.1 1.6 8 f/22 2.3 1.1 4 (As shown on lens) (50mm divided by f/stop) (1/2 the diameter) (pi X the radius squared) If you look down the column of figures on the right, you can see the (more or less) doubling/halving going on up and down the column. You can see also how the big numbers make for smaller areas since the f/stop number is being divided into the focal length, then halved, then squared, then multiplied by π. It's no wonder this seems obscure.

Why not just call for the aperture area directly? A couple of reasons. First of all, if you have a 50mm lens on and say "I shot this with my 50mm at 1/125th and an aperture area of 63 square millimeters" you will impart correct and exact information that precisely zero people will understand. It's way easier to say "I shot this at 1/125th at f/5.6". Also, 63 square millimeters is f/5.6 only with a 50mm lens. If your lens is a 35mm, or an 85, or a 300, the ratio is changed around and the exposure is different. In fact, that 63 sq. mm is about f/4 on the 35mm, f/9.5 on the 85mm and f/32 on the 300. Knowing only the area of the aperture requires also knowing the length of the lens also to be informative as to the amount of light coming through the lens. The f/stop figure incorporates both of these in one useful if initially confusing measure and the lens length is immaterial. It's shorthand, in effect. When you say f/8, you mean for this focal length (the f?), give me an aperture whose area is such that diameter of the resulting circle goes eight times into my focal length. Fortunately, the lens makers figure out all these things for us and just mark the f/stops on the lens for us. They're doing us a big favor.

Got it. What about other f/stop terms?

[v22TTC]

Well, between you guys and my 15 year old photography knowledge resurfacing I think I'm sorted now! It's handy that the industry kept the same nomenclature for digital as for the analogue I was familiar with... what are the chances of that?!

So, one last question (for now) - reckon the Nikon P80 is the one... buuut it isn't released in the UK until April 25th... two days before the IP deadline... so from people's experience, how reliable is the release date for cameras?

[goblyn13]

Well, between you guys and my 15 year old photography knowledge resurfacing I think I'm sorted now! It's handy that the industry kept the same nomenclature for digital as for the analogue I was familiar with... what are the chances of that?!

So, one last question (for now) - reckon the Nikon P80 is the one... buuut it isn't released in the UK until April 25th... two days before the IP deadline... so from people's experience, how reliable is the release date for cameras?

With the computer industry, I wouldn't count on that one to be arriving on time. With how most of the computer industry works and all the middle men, the release date means the date which the manufacturer will begin shipping the product to the distributors.

[Wren]

Any chance you could borrow something from a friend for the first round to tide you over if it doesn't release on that date?

[v22TTC]

Only the camera I am borrowing but you can't manually set most of it and it's a little diorama I'll be doing so I'm worried about depth of field. It also has a 12cm minimum focusing distance and I really wanted to get in close to capture the main part of the diorama to save wasting KBs on `empty space', without having to use zoom....

There's also the time spent learning how to use two cameras, which might be significant or not.... I think that this might be another thing for Round 1 where I actually lucked out (all things considered) given that it will be a monochromatic scene with an overall impact so the little details don't matter quite so much.... Ah, I'm sure it'll all be grand - be grander though if I get that sweet P80 in time....

[Wren]

I don't think people usually get quite that close to take pics of minis. I shoot fairly close, between 8-12 inches, but lots of people use 1-2 feet. You'll sometimes find it easier to focus, particularly with depth of field issues, if you pull the camera back a bit. I've tried using my camera's super zoom and getting right 'in the face' of the mini, and the pictures tended to have a lot more lighting/colour issues than ones with regular macro at a slight distance. Got some neat stuff of snowflakes and such one time though.

Also as long as you're using optical zoom to frame the pictures you're fine, that's the lens moving closer. Digital zoom is the bad one because it's doing a crop within the camera and losing information. It's almost guaranteed you'll have to do some cropping yourself in an image program, and possibly balance levels or a few other things to get the colour spot on. I post fairly large pictures, and they're still usually resized to 1/3 or 1/2 the size of the image from the camera after cropping out extensive dead space around the edges of the mini.

For your borrowed camera, try focusing on something in the center zone of the diorama, that sometimes helps with depth of field. I've found the learning time on taking pics of minis to be an ongoing thing. Every 6-8 months I have an Eureka moment of trying something different with a setting or improving my backdrop or lighting method or whatever. Learning to use an image editor well is another ongoing process for me.

[v22TTC]

Had a bit of another play with the camera today and it turns out you can actually manually set even less than I thought... but - the pics turned out pretty sweet.

Perhaps it's a magic camera coz it actually made my three-quarters painted minis (not IP ones) look better than they do in real life!... And the reds are to die for!

Have to be careful not to use this to cheat with IP!

[Wren]

Sounds like my old camera, it liked the reds a lot. This one shifts heavily to green in macro mode, though doesn't seem to in regular mode. I have to muck about a lot with levels even though this is a more expensive camera with more manual options. Probably just something I haven't figured out right in set up.