Linda From Maine Loc: Yakima, Washington

rmalarz Loc: Tempe, Arizona

Yes, they see through the lens. However, there is a bit of lag between what is happening in front of the camera and what you see in the eyepiece due to the electronics involved in relaying the image from the sensor to the eyepiece, which is actually a very tiny monitor. That lag can vary from very very slight to noticeable depending on the make and model.
--Bob

jackm1943 Loc: Omaha, Nebraska

Isn't there always a little delay in the LCD image that one sees? Or has technology reduced this delay to where it is no problem. I remember it being fairly noticeable with an older mirrorless camera (old Lumix) that I have.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

YOU do not view through the lens. The electronics of the camera views through the lens and presents you an electronic image of it through the eyepiece or the back screen of the camera (just like a TV image). But what you see is what you get.
One big advantage is that as you change exposure compensation on your camera the final result can be seen through your eyepiece so there is no longer a need to guess. What you see on exposures is what you get. Neat.

Kreb's Cyclist

If I may hijack the thread momentarily, I also have a question.....with mirrorless cameras do you need to worry about micro focus adjustments when the lens is having back or front focusing issues? I'm thinking that's not an issue with mirrorless.

dsmeltz Loc: Philadelphia

Actually, mirrorless is MORE wysiwyg than a DSLR. The mirrorless shows you what the sensor sees and will record based on your settings. DSLRs do not.

chapjohn Loc: Tigard, Oregon

I would think this applies to mirrorless cameras in general, but I will only speak of Sony mirrorless cameras. What you see in the viewfinder is exactly the same as what you see in live view. There is a setting that can be turned on or off, that when on will automatically sense you are close enough and turn off the live view and show in the viewfinder or vice-versa.

Low Budget Dave

Also, in most mirrorless cameras, you can "gain up" the viewfinder. That means, even in dark situations, you can look through the viewfinder and see what you are taking a picture of, even though a picture might come out black. This is useful in situations where you are going to take a two-second-long exposure.

amfoto1 Loc: San Jose, Calif. USA

I think you mean the camera sees through the lens (not the "mirror", since there is no mirror ).

OP, other responses are correct. Both types of cameras have through the lens viewing of the scene in front of them. DSLRs do by reflecting the image with a mirror into a pentaprism arrangement, where it's redirected to your eye... and optical viewfinder arrangement. Mirrorless cameras use the sensor... the same sensor that makes the images... to "see" through the lens. What the sensor is seeing is then transmitted to a small screen within the electronic viewfinder, where you can see it with your eye. WYSIWYG.

There are advantages and disadvantages to both.

SLRs/DSLRs with their mirrors require great precision orienting the mirror and the optics of the pentaprism to coincide exactly with the image taking film/sensor plane. It's much simpler in mirrorless since the same surface is being used both for viewing and to make the image. For this reason, many DLSRs have means of adjusting focus accuracy. A micro focus adjustment feature is unnecessary with mirrorless.

Mirrorless cameras also can amplify an image in their electronic viewfinder, to brighten up low light scenes you'd have difficulty seeing through a DSLR's optical viewfinder.

In fact, many mirrorless interchangeable lens cameras (MILC) emulate exposure right in the viewfinder, showing you a pretty good approximation of what the camera's current settings will render in the current situation. Many DSLRs can do this, too... but only on their rear LCD monitor in Live View mode. So you can keep the MILC to your eye and make adjustments to exposure settings by feel, where to do the same with a DSLR you'd have to move the camera away from your eye to use the LCD.

The optical viewfinder of a DSLR is "real time", for all practical purposes. Things seen in an OVF are literally "at the speed of light". In contrast, there can be a slight delay in the image being displayed in the electronic viewfinder of a MILC, as the sensor has to capture it and "send" a signal through the circuitry to the tiny LCD screen in the EVF, where it's re-displayed. Newer MILC have greatly reduced this "lag", to almost equal optical viewfinders. Still, most sports/wildlife/action shooters prefer an optical viewfinder.

Another consideration is that the EVF of the MILC draws power continuously while in use. The sensor has to be active continuously too. An optical viewfinder in a DSLR draws no power at all and the camera's sensor is only activated during the instant of exposure (unless it's used in Live View mode, when it will act more like a MILC). As a result, MILC draw a lot more power and typically get a lot fewer shots per charge than DSLRs do. Newer models have improved on this a good deal. But it can still be a consideration for someone using a high speed camera to shoot a very large number of images at a sporting event or someone waiting in a blind for hours for a critter to come into view. I've shot as many as 9000 images in a day at a sporting event, and was able to do so with just one battery change in each of the two DSLRs I was using. A MILC might require 2X, 3X or even 4X as many battery changes to take the same number of shots and that's a lot more batteries to have to buy and carry around, not to mention the possibility of missing some shots during the "down time" while changing them. But, again, some of the newer model MILC are a bit more power efficient.

speters Loc: Grangeville/Idaho

??...No, they do not have a mirror and do not let you see through the lens!

speters Loc: Grangeville/Idaho

(remember seeing a finger in front of the subject in some peoples old photos, that's because they could not see it, because mirrorless cameras do not let you see through the lens)!

tdekany Loc: Oregon

You are miss informing people. The lag that you are talking about is from 5 or 6 years ago. Today’s viewfinders are excellent in that regards.

Delderby Loc: Derby UK

Rubbage - you are talking about OPTICAL viewfinders, and also TLR cameras, which I grant you, were also mirrorless

Toment Loc: FL, IL

At 120fps in my a6500/, I don’t see a delay. At 60, it’s very minor.
Hope this helps

burkphoto Loc: High Point, NC

No! Not an issue.