why digital SLR

i was under impression that the point of SLR was to see the exact same image in viewfinder as the film sees. but with digital cameras you see the same image on the screen anyway.

so what exactly is the point of digital SLR ? considering that a good digital non-slr is about $600 and the cheapest digital slr is $900 there better by something that makes it specia. WHAT ?

ps: i hope general is the right forum for this Q.

If you are comparing currently available models, the high cost of digital SLR cameras is caused by the large detector size needed to do the job. It’s good to have a large detector though - you get less noise and better low-light sensitivity.

If you are talking about inherent benefits of SLR, an optical viewfinder has far better resolution and response time than a digital display. I have yet to see an on-camera digital display sharp enough to use for focusing. And it’s difficult to make a detector that has high speed and high resolution, so you have to put up with a sluggish viewfinder. This becomes an even bigger problem in low light - if the detector needs 1/8 second exposures to get a clear picture, the viewfinder can only be updated 8 times a second. Less, actually, since there’s an overhead for readout and processing.

The ability to change lenses with a wide array of 35 mm cameras is one of the biggest benefits. Being able to use a lot of other standard 35mm accessories is also nice (flashes, filters, etc.).

Non-SLR digital cameras usually have pretty pathetic lenses. They may be good quality lenses (or, quite frequently, not), but optical zooms in the 3-5x range really limit those cameras usefulness. A digital SLR, on the other hand, can take any one of hundreds of different lenses on the market, or could be adapted to attach to things that the non-digital cameras would have a hard time with, like telescopes.

I think the OP was asking why digital cameras with interchangeable lenses need optical viewfinders. The OP is correct that a reflex mirror setup is not strictly necessary - the camera could just read out the CCD and display the image on an LCD screen, and it’ll work just like an optical viewfinder. Except for the limitations I listed above.

SLRs are generally beneficial for pro photography. Basically, there’s a lot more manual control involved, as far as flash, customizability, focus, shutter speed, etc. The viewfinder issue is not the only advantage or appeal of the SLR.

Is battery life also an issue? - illuminated LCD screens consume quite a bit of power and serious photographers often use their cameras for extended periods.

A large advantage of DSLRs is the response time of the shutter. With most point and shoot cameras, the time from hitting the shutter release to the actual taking of the picture can be unacceptable for action shots.

Also, the higher ISOs tend to be less noisy on DSLRs than on point and shoots, related (probably? not sure) to the larger sensor size, which enables each pixel on the CMOS/CCD to recieve more light - resulting in less noise.

I interpreted the question to be more along the lines of “Why would someone spend $900 on a camera when there are $600 cameras with similar capabilities?”

To me, being able to use a lot of the equipment I already have is one of the reasons to get the $900 camera. The CCD size and manual focus are also significant issues, but you had already covered them.

One simple reason:

The picture you see on the digital view finder is NOT the picture you get later. In most digital cameras I’ve had a chance to fool with, the digital view finder would crop something off of the edges - I’ve taken photos where I thought (as I snapped the picture) “Oh, damn. I cut the feet off of another one.” A preview (in the camera using the view finder) would verify the impression and I’d shoot the picture again. At home, I’d pull the photos from the flash card and find that both images had feet.

The digital view finders suck at real time - they all lag somewhat behind. They are also relatively grainy - I can’t check focus with them, and have to trust the automatic focus.

If the only view finder is a screen on the back of the camera, then it isn’t of much use in sunlight - the picture is too washed out by the ambient light.

I own an Olympus 2500 - SLR, but can’t change lenses.

Also, the tiny digital screen on the back of the camera is near useless in certain bright light situations.

One issue I don’t think was mentioned is that some large CCDs an CMOS sensors used in DSLR cameras cannot provide live video to a LCD viewfinder. This may change in the future but for now all the best technology is being put into DSLRS because a lot of it already existed in film SLRs.

Things are evolving though. Both Nikon and Pentax make cameras that take existing 35mm film lenses and use the same APS sized sensor from Sony but the cameras are different. The sensor is about 2/3 the size of a 35mm film frame so they have a “crop factor” of 1.5. That means a 50mm lens will have the angle of view of a 75mm lens. Nikon’s D100 is based on the N80 film camera and has a full size mirror and vewfinder only slightly modified for the smaller frame. The Pentxax *istD (weirdest damn name I ever saw) was designed from scratch to be much more compact and has mirror, shutter and viewfinder sized to the smaller frame. The Pentax is actually smaller than the Olympus E-1 which uses an even smaller 4/3" sensor.

I’m not disputing this, but it makes absolutely no sense, unless it’s intentional. Any digital cams can easily be better at this than an SLR.

I have to agree with SmackFu. Some cameras do crop in the LCD but this isn’t common. Low end DSLRS - costing less than $2,500 - typically only show 95% of the actual frame in the viewfinder. The new ultra low price Canon Digital Rebel DSLR has about that same coverage but users are reporting quite a bit of misalignment, so much that a sliver of what is seen in the viewfinder is not captured by the sensor. High end pro DSLRs likle the Nikon D1/D2 series which is built on a Nikon F100 body and the Canon 1D/1Ds have 100% viewfinder converage and those cameras cost over $3,000.

aaight, thanx.

interesting points on lcd screen being sluggish, grainy and washed out in daylight. although some cameras have an lcd viewfinder so that daylight is not an issue.

having a camera with interchangeable lens would be nice, cuz indeed 3x zoom found on most cameras is often not enough. but i could really do without the SLR part.

Digital SLRs are mainly intended for professionals who need the extra functionality that the setup provides, e.g.:

– Seeing exactly what’s going on the “film”, so you know exactly what you’re getting and don’t have to crop later. Cameras with a seperate viewfinder are generally way off.

– You need to see things in real time, for sports and such; LCD displays have some lag.

– Wide range of interchangeable lenses, so you can have 17mm super-wide for closeups of big things, to 300mm (or more) for small things far away, especially sports.

– Long battery life, so you can work all day in fairly remote locations; this is one of the main drawbacks of electronic viewfinders.

– Quick response time, for sports and other action shots. You need the shutter to trip immediately when you push the button.

– Ability to manually focus.

Point-and-shoot cameras with electronic viewfinders work fine for taking a snapshot of little Jimmy at his birthday party, but you really need an SLR to get a closeup action shot for the newspaper’s sports page.

You don’t realize how much nicer an SLR is until you use one. I love my (well, my employer’s) Nikon D1.