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Comment by sathackr | Hacker News Reader

Just curious...what's the big deal with a DSLR?

I really don't even see a need for the complexity of one anymore.

The SLR camera was designed so that you could see the actual scene through the same lens that would be taking the picture. Mirror in place, light goes to viewfinder. Take a picture and the mirror moves so the light can go to the film instead.

But on a digital camera, there is a live view of the scene on the screen on the camera. Who wants to put there eye to the tiny viewfinder when they have a 3" display of the same thing. Without the need for a viewfinder, there is no need for a moving mirror inside the camera. Just project the image directly onto the sensor.

Do people with DSLRs still use the viewfinder? If so, why?

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Autofocus is also a fairly important reason. The Autofocus in SLRs uses many dedicated AF points with a secondary mirror that connects to the phase detection sensor. This is faster and more accurate than what is used with Live view. In live view, Contrast Detect is used, which in most cases is still slower and less accurate, especially as the available light falls off (either from a darker environment, or from a lens with a smaller maximum aperture).

Lenses are a big factor too, at a certain point you are limited by the maximum resolution of the glass/sapphire/flourine whatever. High resolution / sensor area cameras run into this issue. larger lenses allow for larger sensors, which means lower demands on the glass. Typically, SLR lenses are nicer in the first place, or at least have higher end products available. For very high-end photography, you still see medium format cameras for this reason.

> Autofocus

Thank you! I wasn't aware of the various methods to autofocus. It makes sense that having a mirror to send light to a dedicated sensor would be better.

I remember an older camera my mother used to have used some sort of ultrasonic device for ranging -- I remember it would make a 'click' sound anytime it was focusing.

>> Autofocus is also a fairly important reason

This isn't exclusive to SLRs. These days, all the top mirrorless cameras have on-sensor phase-shift AF sensor pixels across the entire frame. Also, not all cameras use contrast detect in Live View. For example, Sony's DSLRs were the first (and maybe only) DSLRs to use a secondary PDAF sensor for Live View. Yes, you can get slightly faster PDAF on an SLR, but the gap is very narrow these days. The often mocked Nikon 1 mirrorless series can AF track just as well as most consumer DSLRs.

>> Lenses are a big factor too

Once again, this isn't exclusive to SLRs. This is more about sensor size than whether the camera has a mechanical mirror box inside.

>>This isn't exclusive to SLRs.

No, it is not, but, for a given price point, you will likely get faster AF with an SLR today than all but the most expensive mirrorless cameras. Especially with motion tracking. I know that there are some cameras that say they'll be faster, but having tested a bunch in the real world, I had a very hard time finding any that worked as well as SLRs in as wide a range of conditions.

>>This is more about sensor size than whether the camera has a mechanical mirror box inside.

Yes, though it is more complex than this. It also has to do with the distance from the sensor to the back of the lens. This doesn't require a mirror, but most mirrorless cameras are focused on reducing the size of the package, so they try to reduce this distance so they can shrink their lenses. This is not an absolute advantage of the SLR, but the form factor currently lends itself to this characteristic, while mirrorless bodies are typically trying to optimize for something else. (of course, many mirrorless cameras can use adaptors to full-frame SLR lenses, and the results can be great image quality, but typically bad performance on autofocus.)

source: Spent several days with A7R, A7R2, Canon 6D, 5D3, 5DSr. Tested lenses Canon 11-24, 40mm, 24-70ii, 70-200, sony 70-200. Ultimately bought the 5DSr, due to more reliable functioning, ergonomics, lenses, battery life, etc. Despite genuinely wanting to shed the weight.

>> No, it is not, but, for a given price point, you will likely get faster AF with an SLR today than all but the most expensive mirrorless cameras. Especially with motion tracking. I know that there are some cameras that say they'll be faster, but having tested a bunch in the real world, I had a very hard time finding any that worked as well as SLRs in as wide a range of conditions.

Practically speaking, most non-enthusiasts don't turn over their cameras every two years. So there are plenty of DSLRs in the wild that mirrorless cameras can outperform. My Nikon V1 (hardly a new camera) can outperform a Canon 5D1 in AF speed in just about any situation, and rightly or wrongly, my V1 is considered to be a joke by many enthusiasts.

It's about as fast as my APS-C DSLRs from 2008 and 2010 -- and keep in mind, that a DSLR from 2008 is probably more than fast enough for most non-enthusiasts today. Newer mirrorless cameras can perform about as well as slightly older consumer DSLRs in terms of AF. And for most people, it's a fair compromise for the size differential.

>> Yes, though it is more complex than this.

No disagreement there, but you're speaking from the context of an enthusiast. From a bigger picture perspective, most buyers of consumer DSLRs (which are the majority of DSLRs being sold) aren't pixel peepers. They just want better photos of their kids and pets, etc. Most of them could be easily satisfied with an iPhone 7+ with portrait mode or a Sony RX100MK1.

The benefits you speak of are very true for a segment of photographers but I question whether they apply to the person who simply wants better quality images than they get from their smartphone or cheap point and shoot.

>a DSLR from 2008 is probably more than fast enough for most non-enthusiasts today

I was selling some older DSLR equipment recently and it made me think that someone wanting to learn photography with a "real" camera today can do quite well with older gear. It won't autofocus as well or have as good a sensor but it can be plenty good to learn on. Lenses of course don't degrade in value quite as much but there are plenty of lenses that enthusiasts may sniff at but are plenty good for a beginner.

It is MUCH more stable to shoot looking in the viewfinder with the camera pressed against your face than holding it out in front of you at arms length. There are smaller SLR cameras now that are mirrorless and use a variety of means to provide a viewfinder because it is still a much better way to shoot.

>> There are smaller SLR cameras now that are mirrorless

Hate being pedantic but a mirrorless camera can't be an SLR.

:-) Unfortunately none of the other names for mirrorless/interchangeable lens like EVIL really stuck while SLR is really an anachronism because it was in contrast to twin lens.

Exposing the sensor at the last moment (when the mirror moves into position and the shutter opens) results in decreased noise compared to live preview. I think this has to do with residual charge and heat on the CCD. Also, in some situations an LCD is hard to see, whereas the optical viewfinder has no lag, has fantastic picture quality, and looks right through the lens, which is great for all sorts of situations.

Great information -- I hadn't thought of that. I tried googling my question first and didn't get very far.

I actually tried googling for a source for what I was saying and didn't find anything. It's what I've always heard, and it makes sense.. but everything I found was talking about other issues with noise (and talking about audible noise from the mirror movement, heh.)

For some, it's a matter of preference. But there are good arguments for it - the viewfinder isn't limited by display resolution, for example. On the other hand, modern mirrorless cameras are marvellous, too. For example, the camera can bring your attention to areas that exceed the camera's dynamic range (and would thus be too bright / too dark), or highlight exactly which bits are in focus.

So the digital versions are getting better, but there are still reasons to use an analogue viewfinder. It's not as clear-cut as you think. I encourage you to try it out!

Fidelity and ergonomics. In addition to a DSLR I also use a Fujifilm X-E1 with an electronic viewfinder. It's much preferable (IMO) to hold a viewfinder near my eye, blocking out external light, with my elbows stabilized against my body than to hold an LCD panel out in space squinting to see the image in bright sun.

In addition, although I use the X-E1 a lot for travel, the DSLR's optical viewfinder is still superior optically and the camera as a whole is faster, more responsive, etc.--in part because it's bigger and the designers have more space to work with.

I do think we're headed toward a point where electronic viewfinders will tend to replace optical ones but I doubt we'll replace looking through viewfinders.

Battery life also makes a huge difference. If you use just the view finder on a dslr you can take many hundreds of pictures on a single charge.

It's the delay between the live image and the image on the screen. For certain situations ( like wild / nature photography / sports ) , this _is_ a limiting factor.

For selfies, not so much.

big deal with the DSLR: until very recently, if you wanted a large high-quality sensor you needed a DSLR (or medium format, but that's a totally different can of worms and level of pricing). They still are ahead in high-performance auto-focus systems and selection of really good lenses, but mirror-less cameras are getting closer and closer there as well.

The vast majority of enthusiast and pro users uses the viewfinder regularly, if not exclusively. Professional mirror-less cameras basically have to have a (digital) viewfinder.

* The 3" screen is a lot smaller compared to the image you can see through a viewfinder, and doesn't fill your field-of-view as much. Fixed with digital viewfinders.

* thus, many people find it quite hard to get a good impression of the image with a screen.

* The screens have limited resolution and delay. Resolution is especially a problem with digital view finders.

* In many DSLRs, using the screen limits the auto-focus performance.

* In bright conditions, the back-screens are hard to see. (Esp. if it is a touch screen with smudges on it ;))

Having both options is great, digital displays add a lot of features as well: focus-peaking, brighter image in low-light, easier to use the camera held high or close to the ground. Mirrorless cameras with digital viewfinders are becoming more and more popular, but the viewfinders won't be going away.

re: what's the big deal with a DSLR?

1. Full manual control. I can dial in exactly the combination of f-stop and exposure that I want.

2. Manual focus. With a split-ring screen in the viewfinder, focus can be very precise and exactly where I want it. Both for getting the right part of the image sharp, and controlling depth of field.

3. Interchangeable prime lenses. Changing lenses makes a big difference in the results. Different lenses do different things: a fisheye, a wide-angle, a macro lense; each is really great in one particular area.

4. Lots of accessories. You can turn a DSLR into a decent rig for shooting pro quality videos or a low budget film, if that's your thing. You can add extra batteries, extra storage, and so on.

DSLRs are generally worse than mirrorless cameras when it comes to live view on the rear LCD, because of the mirror and "double-clutching" to activate. With a competitive mirrorless camera, which may get more to the heart of the question, use of the electronic (not optical) viewfinder and live view is pretty equal.

So why would one use the EVF over the LCD? I think the most common answer is, "being able to actually see in bright sunlight."

>> So why would one use the EVF over the LCD

The diopter is also a big reason to use an OVF/EVF.

I have to wear reading glasses now, so it's an inconvenience to use the LCD.

BUT, I have found that touch screen LCDs that support tap to focus+shutter mitigate that problem. In normal circumstances, I don't need precise focus (faces tend to be big enough) that I can still get decent shots even though the LCD is blurry to me.

There are a few reasons for why the viewfinder is preferred, but the two biggest that I can think of are:

- No lag - No battery drain

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