MAMA's Techno-Geek Thread

[blalor]

Oh, hey, that D200 can link up with a GPS! Guess who'll be geolocating our outings from now on?

[GBMINI]

Quote: Originally Posted by blalor (original)

One of the factors when I chose my Canon was that [url=http://photoshopnews.com/?p=226]Nikon encrypts the white balance information in their raw (NEF) files[/url

I remember you talking about that Brian ... I think part of the reason I ended up with Nikon was that it's what the salesman uses; but that lens was the clincher. We spent ?an hour? checking cameras and I nearly picked up the D80 or the Rebel XTi ... but in both cases we were only half done, I'd next have to figure what lens(es) to get.
The D200 was an "idiots choice" coming with the wide range lens (OK, and idiot-with-moneys-choice, but ...)

I have no idea if I'll use the RAW ever - but I like the feature that the D200 can record both JPG & RAW at the same time; I could use the JPG generally and bail to RAW if there was something special needed (mind, <200 pics on the 4GB card that way!)

[GBMINI]

Quote: Originally Posted by blalor (original)

Oh, hey, that D200 can link up with a GPS! Guess who'll be geolocating our outings from now on?

Didn't buy that gadget

[blalor]

The ƒ-number is an expression of how wide open the aperture of the lens is. I think an aperture of 1.0 means the iris is completely open, while ƒ/16 is very small. I forget the progression, but each higher number represents a halving of the open area of the iris. Aperture and shutter speed are directly linked in that they control how much light reaches the sensor. At a given aperture/shutter speed pair, if you open the aperture one stop you send more light to the sensor. If instead you slow the shutter speed, you *also* send more light to the sensor. It's a balancing act. The other thing you impact with the aperture is the depth of field. For example, this picture of Josh's duck was taken with the aperture wide open:
(click for bigger)
Note how the duck (which is what the camera's focussed on) is sharp, but the background is blurry. If instead I'd taken the shot with the aperture at ƒ/16, the background would also be sharp. But to expose the scene properly you'd also have to decrease the shutter speed.

[blalor]

RAW is really powerful, but it also adds a step. Another trade-off! Yay! I used the RAW+JPEG setting for a while, but now I just shoot raw and use Aperture. I don't *have* to do any fine-tuning to get a JPEG (or, most of the time, just upload to Flickr): I just import the picture into Aperture and then export the JPEG with a click or two. But I just this weekend realized how much information is really available in the RAW file; I had a shot that looks pretty overexposed in places (like there's no detail in the sky because it's too bright). Playing with the exposure slider I could pull that detail out (while making the rest of the scene much darker). Someone with an iota of Photoshop knowledge could decrease the exposure of that part of the scene without sacrificing the rest of it. It's definitely a more advanced thing. You're better served right now by spending time behind the viewfinder!

[blalor]

What Is... Aperture? - Digital Photography Tutorial - Photoxels

If you can stand the shameless self-promotion and roughly 60/40 blather/content ratio, there's a digital photography podcast called "Tips From the Top Floor" with a very smarmy German host. This is a link to an aperture and DoF episode:
tftf44 - Aperture vs. Depth-of-Field at Digital Photography Tips From The Top Floor
and this one talks about what the various ƒ-numbers mean:
tfttf149 - Apercadabra! at Digital Photography Tips From The Top Floor

[snid]

Somewhere on the camera there should be a "depth of field preview" button.

When you look through the viewfinder, the lens will be "wide open" - the biggest aperture / smallest f number the lens is capable of. There's a button somewhere that will "stop" the lens down to the currently selected f-stop, letting you see the depth of field (what's in focus) that the picture will be taken at. The tradeoff is that as the aperture gets smaller, less light comes through, so what you see through the viewfinder gets darker. But, it can be fun to play with.

There also might be focus indicator numbers on the lens body itself. There's a hash mark in the center, and going out on both sides of that various f numbers. These will tell you what range of distances will be in focus at what f-stop. I'm not sure if the fancy new digital lenses still have those markings on them. If they do, they're probably really small and hard to read, unlike the old school film stuff.

f-stop is a fraction of some sort, hence it being written as f/2.0 I believe it's the ratio of the aperture diameter to the focal length. But I could be off on that.

Whoops, forgot to mention one of the more concrete examples of f-stop / aperture stuff. Big f number, small aperture (hole). Taken to an extreme, you have a pinhole camera (or point and shoot) effect... everything is in focus all of the time (pretty much). The other extreme, really big aperture, only a tiny amount of the picture is in focus.

f/4 is pretty wide open for a zoom. f/2 is reasonable for a cheap prime lens. Below f/2 gets expensive (usually).

Zoom lenses will usually have a range of biggest aperture available depending upon the focal length you are at (how zoomed in).

[NoNo]

The DOF button on my D70 is to the lower left of the lens. And if it's like my camera, Ian, when you look through the viewfinder there should be a bar to the bottom. You want your settings to get that as near to center as possible and that should get you a properly exposed image.

[jwardell]

Quote: Originally Posted by GBMINI (original)

without flash it took I think a 3s picture of the wallpaper, but I was astounded that hand-holding it, there was still almost zero blur! I don't know how VR works, but it seems incredible; I'd expect hand holding the much heavier D200 to be worse than hand holding the previous ones I've owned.


Clarification please on "f" numbers ... how do they relate to shutter speed?
Josh, you say this 18-200 lens is 3.5 at wide and 5.6 at zoomed - what does that mean for shutter speeds?
(sorry I bet I could Google it, but I have a wealth of expertise right here )

The heavier the camera, the less camera shake/blurring you will get. That's why those steadicams they use in the movies involve weights and strap on to your back and waist.

The VR system uses accelerometers and actuators to move internal lens elements to cancel small movements. Obviously they can only move so far for so long, but in general they are good for an extra stop. That means, you can get away with a twice as long shutter speed. Or, shooting at 200 instead of 400. Or using a higher aperture. See how each of these values are tied together?

Some manufacturers are now adding a similar system to the sensor, that way no matter what lens is used, you get anti-shake features. It's also easier to do and has allowed them to add it to point and shoots as well..which really need it. But in reality it is not a life saver. It helps a little, but if it's too dark, it's too dark.

Another tip in shooting in dark lighting is to simply zoom out. The more wide angle you are, the less an effect a given motion has on the details of the image. The lens lets in more light as well, allowing a lower aperture and therefore a higher shutter speed.

[GBMINI]

OK, a little "play & show" ... a few pics I took late last night.

0001 was taken "wide" with the camera just turned on - ISO 100. The pic data says 18mm focal length, F/3.5, 3.6s exposure. Remember this was held in the hand!

0002 is the same except I bumped up to ISO 640 (seemed like a nice number!) so now the exposure is down to 1/2s.

0007 is zoomed in (it says 60mm?) with flash, so F/4.8 & 1/60s.

0009 I did just now, max zoom into my work LCD (F/5.6, 1/3s).

[Theo]

Ahhh...

I remember the days of shooting film in my old and trusty Minolta SRT-101 with a f1.2 50mm lense. Spent an entire afternoon deep in a forest shooting roots, moss, and other ground level objects in natural light.

That camera was incredibly sturdy for its weight; at one point it rolled down a mountain and still operated perfectly. I took it to the camera shop when I returned from my trip and had it checked out...slight shutter adjustment, but that's all!

Think the cameras today are that sturdy?

Theo

[GBMINI]

And here's some cropped parts of the above ...

Obviously 0001 has some camera shake - but this was an exposure of over 3s; I'm very impressed with the "VR" / stability feature! And yes I know I shouldn't be using the camera like this, but if I do ...

0002 with it's higher ISO and quicker exposure seems to show zero camera shake - it was still 1/2s hand held though!

0009 indicates the lack of clarity in the LCD rather than the camera picture (again 1/3s F/5.6 @ ISO 100, max zoom)

[GBMINI]

OK, one last "play".
This is taking a phone list on the wall at maximum (200mm) zoom. F/5.6 @ 1/8s. ISO 100 again.

The first pic is with "VR" turned on, the second is with "VR" turned off ...

[blalor]

The IS (er, sorry, "VR") is pretty impressive, even at those slow shutter speeds!

[MGB Boy]

Quote: Originally Posted by Theo (original)

Ahhh...

I remember the days of shooting film in my old and trusty Minolta SRT-101 with a f1.2 50mm lense. Spent an entire afternoon deep in a forest shooting roots, moss, and other ground level objects in natural light.

That camera was incredibly sturdy for its weight; at one point it rolled down a mountain and still operated perfectly. I took it to the camera shop when I returned from my trip and had it checked out...slight shutter adjustment, but that's all!

Think the cameras today are that sturdy?

Theo

I still have a Canon AE-1P from about 1981. The thing has proven to be a tank, both in terms of durability and weight. You could crack open coconuts with that thing and it would be fine. I use a newer Canon now (EOS 300/Rebel 2000), but it's fun to break out the old beastie from time to time (I've still got a couple FD mount lenses for it). For the newer one, I just ordered up Canon's 50mm f1.8 prime. It's a nice cheap way to get a fairly low f stop, only about $70...

-Ricardo