digital camera question?

"Depth of field" measures the two distances from the lens which are acceptable in focus. For some macro focusing, that is quite small (.1" or so). For some pinhole type cameras, they are in focus from a several feet to infinity, but you have no control over the aperture.

To maximize dof, you need to be able to use a high f-stop (f8 or better). You can do this by using artificial lighting (flash), shooting at long exposure (where you will get motion blur), or you can use a high ASA (400 or higher).

So, look for a camera with adjustable ASA (ISO), long exposure capability (and a tripod mount), or shoot under good lighting conditions.

You don't want extreme DOF under all conditions. For example, if you are shooting a portrait, it is frequently the case that you want the background blurred to draw attention to the subject.

Many cameras in the $400 range will be OK for your use, but don't expect a lot of pro capability. You'll get whatever lens comes fixed to the camera which will likely have some telephoto capability (which reduces DOF if the subject is close to the camera) (note, don't use any of the digital zoom features: they pixellate your image, and you would do better to shoot with full resolution and crop and such in photoshop (I use elements: cheap and pretty good, or iPhoto, not bad either for the Mac).

If you want the DOF adjustments and capabilities you may be used to in a

35mm TTL camera, you are looking at more $$$ for something like the Canon Rebel Digital which uses the Canon range of lenses; or one of the higher end attached lens cameras from Nikon, Sony et al (I own both the Canon 20D and Sony F717, as well as a point and shoot Sony with no features to speak of, but it works).

Mega pixels: Most printers actually print at 300 to 600dpi, no matter what the advertisement says (the rest is various forms of interpolation, etc.); the dye sublimation printers used by oFoto and iPhoto (Apple uses Kodak by the way) or the various Sony's you can buy print at about 400dpi. So a 4x6 inch print is 4MP at 400dpi; 8x10 is 12.8MP at 400dpi.

That said, I've gotten terrific looking prints from my Sony SV55 (403dpi dye sub) and from Kodak with an old 2MP camera, as well as nice 8x10s from the Sony F717 (5MP). So for most work, 4 to 6MP is just fine. If you do a lot of cropping, the more pixels is better; my Canon has 8.2MP and allows for a good deal of cropping without losing detail for a 4x6 print; but it also allows the use of most of Canon's wide range of lenses, so framing the shot while taking the photo is easier than a camera where you are stuck with what came glued to it. Ed

in article snipped-for-privacy@news.commspeed.net, Arizona Rock & Mineral Co. at snipped-for-privacy@northlink.com wrote on 12/6/05 7:22 PM:

That will buy a lot of camera. What you need to look into is how well the manual mode of the camera can be accessed & used, to change the shutter speed for the depth you desire.

5.0 MP would be the minimum nowadays. For special effects & maximum flexibility, you can almost get into a digital SLR for that money. Otherwise, get a point & shoot w/ good optical zoom.

Rob

Depth of field normally increased by stopping down, I don't know that you're going to get any better with a digital. I don't know if they even have a diaphram or if that's taken care of with electronics. IF it's done with a diaphram, you might be able to force it to stop down by really pouring on the light, as with photofloods.

If you're working close up, well... Even my best macro lenses didn't have much. Right now I have five digitals, and the oldest, Olympus D600-L still has the best quality, but at a kilobuck was still the most expensive. No substitute for good lenses. Fuji has one in the $250 range, The S-3000 that's kinda nice, but not the quality or accuracy of exposure. Not sure of Nikon, or Kodak, don't have much interest in either brand.

Some digitals will let you adjust the program, to force longer or shorter exposure times, not sure how that works. Longer time means stopped down, which hints at a diaphram.

Rich

Richard spake thus:

They have to have diaphragms, because without one the lens will have shallow depth of field. Dunno how exactly this is done: in some cheap cameras, there's a wheel with several fixed stops rather than a real iris diaphragm.

To answer the OP's question, depth of field is *not* a function of a better or more expensive lens; it's simply a result of stopping down (using a smaller stop, a smaller hole). The smalla da hole, the bigger da DOF.

FYI there are some programs out there that stitch multiple exposures at different focus depths into a combined photo with increased depth of field.

Here's a link, check it out:

David

David Nebenzahl wrote:

Much depends on what you are going to primarilly take photo's of. If it will be action shots, like trains, cars etc. you will need to look at an Digital SLR. I have a Pentax *istD which I have no problems with, my only regret was to not get a genuine Pentax digital lense with it.

Other Digital SLR's that are good, & I have seen excellent reports on are the Canon D350 in its various incarnations, & the bottom range of NIkon.

Advantage of SLR's is that you can get much better manual options. I have made sure that I take all my photo's in RAW format, as the end results are much better. Its a bit more of a hassle to download to computer, but with programs such as Photoshop Elements, much of the work can be automatically.

If its for happy snappy shots. My son has a Fuji 5.1 mp compact camera, which I must say takes brilliant shots.

The depth of field problem is unchanged with a digital camera. You still need a lens that can 'stop down' to very small openings ... something like F/32 or smaller.

Ultimately, you need a 'pinhole' lens, but these have their own problems. You can't make the pinhole much smaller the 0.020" or you start to get unpleasant diffraction effects. I generally get best results somewhere near f/64.

Digital cameras use shorter focal length lenses as 'normal', compared to

35mm cameras. Shorter focal length means smaller aperture for any given "f" number, which is desirable.

I haven't tried it, but I suspect most of the usual pinhole 'tricks' can be used with a digital camera. A removable lens is a HUGE advantage to implementing many of these. Thus, a digital "SLR" is the most versatile.

You still need the ability to focus close to the camera ... either 'macro' capability, extension tubes, or a 'close-up' lens is needed. These can often be used wit a pseudo-pinhole to improve results further.

The smaller size of the simpler digital cameras is an advantage, however, in getting he camera into tight spots.

Dan Mitchell ============

The good digital SLR's are mostly $700 and up.

A lot can be done with the smaller, simpler, digital cameras, but don't expect superb results when perspectives requiring great depth of field are used.

Optics are the issue ... you need a small aperture. That implies the ability to take a LONG exposure. You need the ability to focus CLOSE to the camera.

A ton of "megapixels" won't help if you can't focus!

Dan Mitchell ============

Megapixels is the least important spec for a digital camera - it matters only if you want to make letter-size enlargements or greater, in which case the printer will be more of an issue than the camera. In fact, two cameras with identical MP specs may well peform quite differently. The lens and software matter much more than megapixels.

The most important component of _any_ camera is the lens. A $400 camera will have a good lens, other things being equal.

Ie, two 4MP cameras, each with 3x optical zoom, one at $200, the other $400, the more expensive one should have a better lens. Ask the geek squad about that. If they can't tell you, go to another camera store. I find that chain stores and big-box stores are _not_ usually the best place to buy. Go to a local, owner-operated shop, the odds are that the owner knows his stuff much better than the minimum-wage 'droids employed by the chains (who save loadsadough by not training their staff properly.) The higher cost for the camera will be offset by the store operator's knowledge eand service.

Now, about depth of field and related technical matters.

Depth of field refers to the range within which the image is in acceptable focus. Eg, say that at 3ft, the depth of field is 10". This means that anything within about 2'10" and 3'8" from the camera is acceptably clear and sharp.

Depth of field depends on the three specs:

a) Distance from the lens: the further away you focus, the deeper the depth of field.

---> In practice, this means that you should be just close enough to get what you want in the frame.

b) The lens's focal length: a short focal length will give a deeper depth of field than a long focal length. A wide-angle lens ("zoom out") has a short focal length. A tele-photo lens ("zoom in") has a long focal length.

---> In practice, you should move in close with the wide-angle setting rather than zooming in to get a close-up. In general, use zoom only if there's no other way. It's often better to select the subject from within a larger picture (to crop it) than to zoom in to the subject.

c) The aperture (opening of the lens). The smaller, the better. But smaller aperture means less light, hence longer exposure time.

---> In practice, this means you want lots of light so the lens can be "stopped down" (the aperture can be reduced). For model pix, that means flood lights. Lighting is a whole 'nother subject.

NB that even with a digital camera, a good lens will be the largest single cost item. Electronics and software are cheap compared to high-quality glass.

In digital terms, this translates into something like the following:

-- 4MP and up

-- a 3x _optical_ zoom or better (ignore the digital zoom, it actually degrades picture quality. Personally, I see no use for it at all.)

-- F2.8 or better (the smaller the F number, the better the camera will perform in low light situations, which you don't want for model photography, but do want for other subjects.)

-- an automatic macro/close-up function (reduces the need for manual setting of aperture etc.)

-- a high quality CCD (sensor) so that the camera doesn't increase aperture too much in low light situations.

-- as many automatically calculated exposure options as possible (reduces the learning curve.)

If you have to choose between fewer megapixels + good lens and more megapixels + average lens, choose the good lens.

The main advantage of digital is that you can play with the pictures, so I also advise:

-- a 512MB or larger memory card (most cameras come with much smaller ones than this)

-- high resolution capability (2048 horizontal minimum) -- set your camera to this resolution, and leave it there.

-- selectable RAW and/or TIFF, and low-compression ratio JPG format.

I prefer a card reader to direct connection to the computer, so I advise you get one of those, too.

Finally, a tripod is a excellent investment, too, especially for model pix.

Oh yeah, batteries: I prefer a camera that uses AA or AAA batteries, since you can get those anywhere. If you get a camera that uses a custom design, make sure that it's rechargeable, and buy a couple extras and charger, too. I've found that my camera doesn't work properly on rechargeable AAs, which produce 1.2V instead of 1.5V. So that's another consideration.

Warning: photography can develop into a hobby that steals time from model railroading. How do I know? Guess!

HTH&HF

I get lost when they say the difference between a $200 5 mega pixel and a $1000 5 mega pixel camera is one has a 1/4 chip and the other has a 1/2 chip . While you need to spend around $800 for the body it always made sense to me to buy a body for lens I already have. I have a older 35mm with lots of good lens and will get around sometime to see if they will fit up to a new body. Also it seems mega pixels somewhat relates to the size of the enlargement you want. A 3 mega pixel camera will do a good 5 x 7 print, etc. However if you want to summit to a mag or for a book then the rules change.

My old Nikon 950 works great on NiMH AAs - too bad it's only 2 MP, but the macro capability is nice.

Phil - As someone who spent more than a decade taking model RR photos of both extreme depth-of-field and close-up, even designing my own pinhole lenses, I can tell you straight away that no digital camera with a price tag of under $400 is going to produce images like most of those extreme close-up, very sharp, excellent DOF, shots often seen in the hobby magazines. The f-ratio of the fixed (non-interchangable) lenses employed in nearly all low end digital cameras are ill-suited to this sort of specialized photography. Until you get up into the category of cameras like the Canon Rebel Digital (I think Pentax makes one now too), with prices of $800 - $1,000 range, and have the ability to interchange lenses, you will not get the kind of results that I infer you are looking for by the wording of your post.

CNJ999

I agree with much of what has already been said. In my limited checking of smaller point and shoot digital cameras, most if not all will only close down to around f/8. This is probably enough for most needs for which they will be used, but will not give great depth of field. But decent photos can be taken if enough care is taken to ensure the main subject in the photo is in focus.

If all of the above hasn't already scared you away and you are still looking for a decent digital, I'd look for one that has the option of manual operations. This is where you can set the aperture (often shown as AV - Aperture Value), shutter speed (often shown as TV - Time Value), and most of all the focus. Some of the higher end Kodak cameras with the 10X zoom lenses seem to have some if not all the features.

Good luck!

Bob Boudreau (shooting with Canon Digital Rebel & Rebel XT) Canada

"Arizona Rock & Mineral Co." wrote in news: snipped-for-privacy@news.commspeed.net:

Well, there has been much technical discussion here about depth of field and how to control it. By now you have figured out that you need to have a camera that has manual exposure controls, esp f-stop or aperature control. And a wide range of available f-stops. f-32 to f-4 (maybe 2) should be a good range. You may have to dig deep into a camera's manual to determine the manual exposure capabilities since most manufactures like to advertise the convience features of their cameras.

I have an Olympus C-740 that has optical zoom and manual exposure controls. Semi automatic mode allows you to select either aperature prefered or shutter speed prefered. I have not delved deeply into these aspects of the camera yet. The C-740 is only a 3 megapixel camera and it has been replaced by simular models with greater megapixels. Certianly worth looking into.

Depending whether or not you want a lot of depth of field or only shallow focus consider this on DOF: a smaller F number (ie f:2.0) means less DOF. A larger F number (ie f:16) means greater DOF. A photographer would refer to the terms larger and smaller in reverse order as an f:2.0 aperture is much greater in area than an f:16 one. Most digitals have an aperture priority mode which allows you to select aperture (f: value). Remember that the flip side of f:16 is a slow shutter speed. You may need a tripod if the light's not right. Bill

It sounds like a discussion on a photography board would get you some useful information.

I expect the result would be the same as asking an experienced camera store (and I have been in several.) This is why I only went to the railroad news group because we force our cameras to do thing unheard of in the photo industry. I tell them about max depth of field and the staff guys look at one another hopping someone knows the answer. I have learned from fellow modelers and this group what is needed. Thanks

They can't tell you about maximum depth of field as a specific number because no one does those kind of figures for a lens or camera. What I did was when I needed a good lens for my digital slr (Canon EOS10D) was when I went to the camera store I told the saleperson what I wanted in terms of the areas I wanted to cover (width, depth) and we mounted up some lenses on a body and checked. Obviously, you sound like that you are going with a non-interchangeable lens digital, so you can't do exactly what I did. What you can do is to try the camera by focusing on a couple of scenes or some such in the store, press off a shot or two, and check the dof on the lcd on the back of the camera.

Most serious photographers complain that todays digital cameras have too much depth of field. I am not sure of the exact relation, but I do know that digital f 8 has alot better depth of field than 35mm f 8.

This is because digital cameras use a smaller image size than 35mm. So you don't need f 32 to get good depth of field.

Your average point and shoot digital camera will take quite good model shots provided it has 2 things going for it.

1) adjustable exposure so that you can use a longer exposure time and the smallest aperature available. Typically f 8...

2) some sort of macro focus capability for closeups.

Then just turn off the flash, and use a tripod to steady the camera and you will get some pretty amazing shots.

Have a look at my online photo album.

these shots were taken with a Canon A80 and only the available overhead flourescent lighting.

Mike Sowsun