There was an interesting question of the D200 user group:

I know its just been 2 days since I bought my D200 but am I missing something or is there no way to shoot while screen is on?

I dont want to look in the viewfinder in every picture I take, there must be a way that I couldnt see in the users manual… 🙁

Okay, I can see all you SLR users there smirking. The person just bought a $1400 camera and doesn’t know that SLRs don’t do that sort of thing because the reflex mirror (the R in SLR). But things have changed a lot. Are we sure we’re not being snobs for smirking?

I know of at least three ways newer SLR cameras get around this problem:

[Understanding live preview after the jump]

A big pro

One big pro of this methodology is live everything: exposure (as long as the shutter speed is faster than the LCD refresh), depth of field, white-balance, and focus. Some of your pocket cameras have “focus assist” where it magnifies an area of the shot. Pretty neat stuff.

The big con

You mean besides cost, complexity and living on the bleeding edge?

The big con of live preview is not dust—the whole sensor is a dust magnet, regardless and it’s certainly not going to be stopped by a mirror.

The big con is always going to be battery life and heat. An optical system uses not much more power than when it is idle. The auto-focus is going to be doing most of that drain in a camera without optical image stabilization (with image stabilization, obviously the keeping those image lens elements stable is going to be using a lot of power).

In fact, the battery/heat issues are going to be so bad, CCD is pretty much dead as a technology to do live preview. The same is probably true with JFET (Nikon D2H), but CMOS is fine.

By “fine” it will still have this issue. Even CMOS sucks battery like mad compared to normal as any Canon dSLR photographer who does night photography will tell you. CMOS on+LCD? Heck, the first thing people like me do with a new camera is go into the custom menu and turn off all the chimping features just to save a few joules.

That’s probably why the live preview on the Fuji S5 Pro is only 30 seconds max.

The three types of live preview

The problem is when someone says “live preview” in a dSLR, they mean one of three types:

1. Electronic viewfinder: the optical viewfinder is replaced by mini LCD. An example is the Sony R1
2. Dual live preview: a mirror with a lot of transmittance so half the image goes to the viewfinder and half goes to the LCD. An example is the Panasonic DMC-L1 or most of the Olympus Four-Thirds line, most notably (and I’ll get to later) the the E-510 and E-410.
3. Mirror-up live preview. The two examples are the Fuji S5 Pro or Canon 1D Mk III. The latter isn’t released and is probably out of anyones price range.

There is a subset up mirror-up live preview in the Pentax line where it basically snaps a shot that isn’t saved to the card. That’s not exactly “live” and if someone could explain how this is better than just snapping a shot, viewing it, and deleting it later if it sucks then I’m open to giving it it’s own category.

LCD viewfinder

This is how your videocamera works. You might be thinking that this is how the optical viewfinder on your pocket camera (assuming it even has one) works. Nope. The optical viewfinder on that—besides being increasingly almost useless—is simply like a rangefinder: in parallel to the lens optics.

But SLRs don’t work that way—that’s the “single lens” part of “single lens reflex.”

However this is the cheapest to implement since you get rid of the entire mirror/pentaprism assembly. There are two big problems here:

1. there is no way that the resolution and speed of this will approach your eye
2. It is unusable in very low light situations

To give you an idea how bad the first is. Even in video (where 1.5 megapixel is considered “high definition”), most pro-videographers prefer a black and white electronic viewfinder because it has better contrast than the color ones.

I own a DMC-LX1 which has no optical viewfinder. When I go clubbing, I am literally shooting in the dark with it. In fact, that’s the one situation where a crappy optical viewfinder beats the pants out of the LCD viewfinder in a pocket camera, and is pretty much the only sort of thing that justifies wasting space on an optical viewfinder in those tiny bodies. (I don’t think it’s worth it, but to each his/her own.)

One place I think this will kick butt is when Sony builds a photo body around their new APS-C 60 fps sensor. That’s going to put the Mark III to shame at a fraction of the price. Heck, for the price of the Mark III, you can get a Red One video camera.

Think about that.

Dual live preview

A dim mirror is not as bad as it sounds. The mirror on a dSLR doesn’t entirely have 100% reflectance. In fact, all mirrored surfaces have light loss. In optical astronomy a big plus is that mirrors are cheaper to make large and have no chromatic aberrations. A minus is the light loss and the impossibility of designing an optical system without a funky transmittance function. Oh well, if there were never any compromises, there’d never be any debates.

Besides mirror attenuation, some of the light is leaked to the exposure and autofocus systems assembly in the camera.

(Technical digression, because I know some of you are big fans of this, using the Nikon D200 as the example: The exposure system sits as a bunch of sensors in the pentaprism looking at the focusing screen. Obviously light is lost there since that’s light on the focusing screen that doesn’t reach your eye. The autofocusing assembly is at the bottom of the camera and a second mirror sits behind the reflex mirror to shine some light into that assembly. Next time you clean your camera, before you flip up the mirror, shine some light into the body and you’ll start to notice things like that. 🙂 )

However what we are talking about is much more than that and your viewfinder will appear much dimmer for it. In addition the LCD preview will need more light than in the previous sytem. Still, the viewfinder has a lot of detail, and it’ll still be better than the previous in darker (clubby) situations.

Having panned this method, I should note that in the Olympus E-410 and E-510, the live LCD has a swivel mount. comes out and swivels. So it’s like having a built in ZigView. No other SLR can claim that (the R1 has this, but it’s more like a ZLR or “bridge camera” because you can’t interchange the lens). That could have come in handy for me more than a few times as I noted in the introduction.

Mirror-up live preview

This is how your pocket camera works and it’s a darn smart idea. Simply flip up the mirror and use your expensive dSLR like a really expensive pocket camera. 🙂

There are some issues here I’m not sure how these companies have figured out all the kinks. As I mentioned above, the lack of mirrors means that the metering and autofocusing system is “dead to you” and all that hard work honing the optical system is gone and this needs to be done entirely differently. I just don’t have faith at this point that it will work nearly as well, though I think that will change and competition and Moore’s law starts to pay dividends.

One thing Moore won’t solve is the heat/battery limitation of running both the CCD and LCD at the same time in this manner.

Finally, let’s face reality: dSLRs are simply not balanced for this sort of photography. Holding a camera at arms length? The thought of doing this with my D200 + 70-200mm f/2.8G ED-IF AF-S VR Zoom-Nikkor…well let’s just say that lens weighs about as much as it’s name. 😀

A recommendation

If after reading this, live-preview may still a deal-killer. My first instinct is to say you should just buy a pocket camera for these times. But…

For the original poster, I really recommend returning the D200 and getting a Fuji S5 Pro (Pop Photo review). It’s the same camera ergonomically as the D200 and it uses the same Nikon F mount. Besides the live preview, it has the Fuji sensor thing going on—a very good thing.