camera flaw or feature?

July 14, 2005 4:22 PM

Hello. I just found out the new Canon D20 digital SLR we use in the office doesn't allow one to use the LCD for framing - it can only be used for playback. This seems odd to me, since the Nikon digital SLR (and every single compact digital camera) I had used previously did. Is there some kind of firmware update or hack that would allow the LCD to be used as a finder? It would be tremendously helpful to be able to use it as such, especially when the icons relating to camera state etc. are all superimposed on top of the image on the PCD. I'm surprised that this camera doesn't allow that, when other digital SLRs (and all of Canon's lower-end cameras) do.
posted by luriete to technology (27 comments total)

This is the nature of the design of an SLR. In an SLR, a moving mirror decides whether the light entering the camera is transferred to the view finder *or* the CCD. The mirror flips for a brief moment to expose the CCD. For the LCD to be used as viewer, the mirror has to be semi-transparent (as in some models, if I recall correctly) or has to stay in the "expose" mode for an extended time. The latter would make controlling exposure a bit difficult.
posted by swordfishtrombones at 4:37 PM on July 14, 2005

If you were able to see a live image in the LCD then you didn't have an SLR.

Why not use the viewfinder? That's what it's for.
posted by bshort at 4:42 PM on July 14, 2005

I realize this. I understand how an SLR works. But then why are Nikon DSLRs able to use the LCD as a finder? It must be possible, as they (and the Kodak DSLRs) can do it, although I'm not sure how they do it. It's tremendously helpful to be able to see a live preview of what the shot will actually look like, taking into account the various compensating filters for tungsten / halogen / sunlight, aperature and ISO, etc.
posted by luriete at 4:45 PM on July 14, 2005

luriete - I have a Nikon SLR: a D70. It does not, in any way, allow you to use the LCD as a viewfinder.

I think you may be confused as to what an SLR actually is.
posted by bshort at 4:46 PM on July 14, 2005

Bshort, if that's true, then I am tremendously embarassed. I have used a D70 in the past and I could have sworn that one could.

I do understand how SLRs work; I've rebuilt a Bronica ETR series, and have owned many F-series Nikons and Pentax/Honeywells and other manual cameras. I guess I assumed there was some kind of magic pass-through sensor or something inexplicable to my (technically not very astute, obviously) mind.

I apologize for wasting space with what I now see is a pretty dumb question.
posted by luriete at 4:51 PM on July 14, 2005

I have the Nikon D100, it doesn't let you use the LCD as viewfinder either.

Even if the mirror weren't in the way, Nikon digital SLRs (and I'm assuming all other brands) also have actual, physical shutters in front of the sensor.

This brings up another interesting question though, which is why do digital SLRs have a physical shutter?
posted by Brian James at 4:53 PM on July 14, 2005

As I've come to understand it (and please, someone correct me if I'm wrong) the compact digitals use a CCD sensor that is turned on and off in place of a physical shutter, whereas the CCD in a digital SLR is "always on" during an exposure, and the physical shutter takes care of the duration.

I'd assume there is a technical reason why the latter is more appropriate for capturing higher quality pictures, but I don't know what that reason is.
posted by odinsdream at 4:57 PM on July 14, 2005

I know Canon made a EOS film SLR that had what's called a pellicle mirror, that was quieter and had less vibration from mirror slap, which is what you're describing, but as far as I know none of the current crop of digital SLRs have this.
posted by bshort at 4:59 PM on July 14, 2005

What would be great would be a camera capable of using interchangeable 35mm lenses (and not a new, proprietary line, but common lenses) which did NOT use a physical shutter. That, I guess, would satisfy my original need.
posted by luriete at 5:00 PM on July 14, 2005

The only cameras AFAIK that have an SLR-type lens and an active LCD viewfinder are the (now discontinued) Olympus E10 and E20, and this is because the lens is not removable.

Having an active viewfinder through the LCD might theoretically be possible with a legacy-free SLR system but isn't going to be a priority for camera makers since it is neither a widely-desirable nor a particularly effective way of shooting pictures with this kind of camera.

If you don't look through the lens to shoot you're not really going to be able to enjoy the kind of control that interchangeable lenses provide in the first place. You might be better off buying a high-end digicam.
posted by selfnoise at 5:24 PM on July 14, 2005

why do digital SLRs have a physical shutter?

The "electronic shutter" function in a CCD works by resetting the pixels, waiting a while for charge to build up, then streaming the charge off line-by-line to the side of the sensor where it is read by a voltmeter and yadda yadda. This causes several problems, mainly related to there not being any way to block more light and therefore more charge hitting the sensor during the shifting process. This is why very cheap cameras have horizontal banding, because while each line is being shifted across, it picks up more charge. You'll also note that the last lines to be read off will have been exposed slightly longer than the first.

(I mainly know video cameras, so this is mostly conjecture)
posted by cillit bang at 5:49 PM on July 14, 2005 [1 favorite]

If you don't look through the lens to shoot you're not really going to be able to enjoy the kind of control that interchangeable lenses provide in the first place. You might be better off buying a high-end digicam.

This is nonsense. Imagine a production-environment shoot for an online catalog where upwards of 10,000 images must be framed and shot with identical settings that preclude point-and-shoot control, swapping a single item in and out of the frame. With the LCD, you can do this much more quickly, subtracting as much as a whole second from the required set-up and shoot time.
posted by mwhybark at 6:07 PM on July 14, 2005

The high end Canon cameras use CMOS imagers, I believe. That eliminates the "streaming" process - each pixel is read out independently. In certain designs it can also eliminate the need for recharging the pixels (depending on whether it's a charge-readout or current-readout process). I think the physical shutter may help lower the "shot" noise of electronic shuttering. Or it may be they use an intrinsic phototransistor, in which case the physical shutter would just be much easier.
posted by solotoro at 6:13 PM on July 14, 2005

luriete I apologize for wasting space with what I now see is a pretty dumb question."

I appreciate the question. I was heavily into photography back in the late 70s using SLRs prior to autofocus. I've been barely involved at all since the mid-80s and have only used the "instamatic-ish" digital cameras for the last several years. I bought a Nikon D70s a couple of days ago. Because the D70s has so much and so little in common with the film SLRs its been a small struggle to get a good feel for exactly how it works. The discussion your "dumb" question elicited has been very helpful to me.
posted by Carbolic at 6:43 PM on July 14, 2005

DSLRs do not allow live previews, as discussed above. If you really insist on this feature, buy a Zigview. [+]
posted by ig at 6:52 PM on July 14, 2005

Imagine a production-environment shoot for an online catalog where upwards of 10,000 images must be framed...

Then you're going to lock the camera down on a huge tripod and it's not going to matter whether you're looking at the framing on the LCD or through the viewfinder.

Also, have you guys ever tried to manually focus a camera via an LCD? It's painful. The Digilux 2 has an electronic viewfinder and it's the sole reason I didn't buy one. Focusing on ground glass, even when the viewfinder is fairly small (like in the D70) is still a better experience than focusing on an EVF.
posted by bshort at 7:20 PM on July 14, 2005

I don't agree. I find it far easier to focus a manual-focus lens via an LCD (although I've only done this a few times) than, for example, with a ground glass or 'split-target' focusing screen on my medium format camera. Certainly it's easier with a waist-level finder, but not a eye-level prism. But I've also had problems with my rangefinder's focusing systems as well, so maybe this is just me.
posted by luriete at 7:26 PM on July 14, 2005

I agree with bshort.

Admittedly I shoot a lot of macrophotography, where focus is both all important and sometimes agonizingly hard, but LCDs just don't have the resolution to reliably communicate focus.

To me, being able to look through the actual, 300 dollar plus piece of glass you're using to shoot is the whole point of having an SLR. (That and being able to move around while doing so.)

Mwhybark- Catalog photography can be done with an SLR, but it can also be done with basically any kind of moderately functional camera. Big-time professionals use digital backs and little mom-and-pop shops can get by with prosumer level digicams. I'm not saying it's not a good use for an SLR, but it's hardly taking advantage of the particular qualities of the format.
posted by selfnoise at 7:41 PM on July 14, 2005

A pellicle mirror does not move but stays in place. This is why it is vibration free and also why you lose about one stop of viewfinder brightness with such systems. The Olympus uses a beamsplitter which also results in diminished brightness. One reason for this is to protect the sensor or the thin filter that sits in front of the sensor. D-slrs are known to have problems with keeping a clean sensor. And cleaning of the sensor can easily result in a broken camera. In addition to this cameras that limit the functions assigned to any individual part tend to be faster. In keeping the pixels from filling you can also help with dynamic range. Keeping the sensor clean however, and the fact that most D-slr's are based on film camera designs are the main reasons.
posted by iwouldificould at 8:07 PM on July 14, 2005

selfnoise, do you mean that you find the point of an SLR is actually looking through the glass with your own eye, rather than seeing a representation of it on a screen?

If DSLRs had "live preview" via either mirror lock up or pellicle glass then the LCD would look through the actual, 300 dollar plus piece of glass you're using to shoot. Even the cheapest P&S digicams look through the shooting lens for their LCD.

That being said, I've grown accustomed to using the viewfinder after my purchase of a Digital Rebel XT, coming from a PowerShot S30. The viewfinder is *tiny*, though. Manual focusing in low-light situations is pretty atrocious, especially since it doesn't have ground glass or split prism focusing. Oh well, that's what I get for buying a low-end "prosumer" camera.
posted by zsazsa at 8:08 PM on July 14, 2005

Zsazsa: Yes, that's what I mean. Even with a poor-quality viewfinder I find that I get a much greater sense of what I'm shooting. I'm not sure of there's some kind of scientific basis to this but I can see depth through the lens in a way that I can't see it on a screen, just as you see depth when you walk down the street in a different way than you see it on television. When you're trying to focus precisely on one part of a small and possibly moving object this ends up being important.

It's possible that I'm just being old-fashioned and inflexible. I'll admit that. Also: we're getting rather far afield from the actual question and I'm contributing to that, so I'll shut up now.
posted by selfnoise at 8:19 PM on July 14, 2005

nitpicking: you see depth walking down the street because you are using both of your eyes to look. You see will see just as much depth looking through an optical viewfinder with one eye as you see looking through an LCD preview.

What you lose is resolution. The Canon 350D is an 8 MP camera, but its LCD has only 115k pixels. That is .115 MP. So when you use the LCD, you only see about 1.44% of the pixels. As a result, the LCD is only potentially good for evaluating exposure, and that assumes that the LCD has as much dynamic range as the digital sensor.

IBM/Iiyama have a 9MP LCD, but it is 22" and costs nearly $9k.
posted by b1tr0t at 10:00 PM on July 14, 2005

Other people have covered this already, but I will state for the record that it's a crime that digital SLRs don't have a ZigView-type setup already built in. You should be able to flip a switch and shift a second, low-res image sensor up into the viewfinder optical path and see it on the LCD for framing purposes. It would cost camera makers about $5 and they'd be able to charge $100 more for it.

If you want a split prism focusing screen on a Rebel XT, click here.
posted by kindall at 10:29 PM on July 14, 2005

I think I sort of rambled in my last post. Shutters are useful for protecting the sensor or filter that sits confront of it. Beam splitters and pellicle mirrors are not really relevant to this.
posted by iwouldificould at 10:31 PM on July 14, 2005

Wow, thanks for that link to the split-prism focusing screen kindall! I was reading this thread and preparing that question in my head as I neared the bottom, and I see you've already answered it. Do you have personal experience with the replacement? I loved the split-prism mirror in my Minolta 35mm SLR, and I'm beginning to miss it using the Canon D-SLR.
posted by odinsdream at 11:08 PM on July 14, 2005

I haven't ordered that a new focusing screen for my 20D, but I'm strongly considering it.
posted by kindall at 12:51 PM on July 15, 2005

I'm a bit stumped by this discussion. I truly cannot imagine how one could efficiently use a SLR camera -- adjusting aperture, shutter and focus over different shots -- while holding it far enough away to view the LCD screen.

Consumers who aren't at all concerned with those settings generally buy non-SLR cameras, which have the LCD screen because they're catering to users who value convenience over precision.

If we are simply talking about an LCD preview screen for situations where aperture, shutter and focus changes are less relevant because of a controlled environment -- such as the 10,000 image product shoot scenario described above -- it makes far more sense to use USB remote software to preview the images immediately at full size on a computer, rather than a low res LCD.

So that leaves framing... Framing? I can't imagine being able to coordinate framing and shutter depression while holding an SLR camera and mounted lens out in front of myself to see a low-res LCD screen in a way that can actually be called "framing" and not "aiming."

That leaves framing via tripod as the only remaining scenario I can find. I suppose that a tripod mounted SLR with fixed a/s/f settings (and probably a remote to preserve steadiness) would benefit from a live preview of what was in the viewfinder... which definitely makes the ZigView a very practical and inexpensive solution for those who are often in such a situation, but far from a necessity for likely more than 80% of SLR buyers.
posted by VulcanMike at 12:47 AM on July 17, 2005