Will a Nikon D5100 (dx format) viewfinder show me what the captured image will be, or do I need to allow for "crop" factor? Will that depend on/alter with using a DX lens or an FX lens? I don't have any prior experience with digital cameras, The D5100 will be my first DSLR. I need this info for choosing appropriate lens.

Also, do the same rules apply if I am shooting with live view mode and then review stills?

  • What do you understand from 'allow for crop factor'? I ask because when I used my 350D (Rebel) I never really noticed or considered it. I knew roughly what it was or could from articles on the web. I just took what I saw in the view finder and went from there. Dec 24 '12 at 2:17

The viewfinder will show what the camera captures, or at least almost what it captures.

Using a lens that supports a larger image circle will not let the camera capture a larger image area, or change the relation between the sensor and the viewfinder.

Some cameras have a viewfinder that shows 100% of the captured images, but it's common that it shows slightly less because it takes very precise calibration of the viewfinder optics to reach 100%.

The live view will naturally show 100% of the captured image, as there is no optical calibration required to acheive that. (Also cameras with a digital viewfinder will show 100% of the captured image.)

As a comparison, an film camera typically shows a bit less than 100% of the captured image by purpose, to represent the final printed result. Commonly the print process masks or crops the image slightly, so that it doesn't show the uneven edge of the captured image.

  • Many consumer grade DSLRs, such as the Nikon D5100, don't show 100%, but they show so close that the different is not relevant to your framing. It might show 98% or 97%, but you are probably not even going to be able to see that. Plus with modern digital photography, you usually want to do at least a small amount of post-processing. All of the tools let you easily crop and straighten the photos, so getting the perfect coverage in the viewfinder is not critical. Even back in the old film days, we usually did enlargements, which allowed some framing errors. Dec 24 '12 at 4:39
  • I don't think it's the optical precision that is at issue with less than 100% viewfinders. I heard that this is done deliberately in lower end models to cater to dumb (OK, maybe "inexperienced") users. Point and shoot user types don't always frame well, so the low end models give you a little extra around what you see in case you cut off the top of someone's head or whatever. Note that the pro models have always had 100% viewfinder. This goes way back to film days. Dec 24 '12 at 16:50
  • 1
    @OlinLathrop: photo.stackexchange.com/questions/11888/…
    – Guffa
    Dec 24 '12 at 17:03
  • "dumb" is Ok with me. This is helpful because I am thinking about framing as first demand. That can't have changed since I used the film cameras 45 years ago. Thanks.
    – John Works
    Dec 24 '12 at 22:35

Your camera (Nikon D5100) shows you about 95% of the full frame in the viewfinder. This has nothing to do with the size of the sensor or that the sensor is smaller than a 35mm frame. The viewfinder and the sensor are built into the same body, so what you see relative to what gets captured is only dependent on the view finder optics relative to the sensor, which the manufacturer can control up front.

Using FX lenses doesn't change this since the viewfinder will still show the same 95% of what the sensor will capture. FX lenses are designed to project onto a full 35mm frame. Your sensor is smaller, so it will capture a smaller area in the middle of the lens's projection. In effect, FX lenses on your camera will appear to have about 50% longer focal length when looking at the final resulting image compared to one taken with a full frame (FX) sensor. Using a FX lens with a DX sensor does no harm, except that the lens will be bigger, heavier, and more expensive than it would need to be if it only had to work with a DX sensor.

  • This is exactly what I was asking. I am excited about getting the camera, but don't have it in hand yet. I may have access to some FX lenses, however, and am just wondering how to think about using them.
    – John Works
    Dec 24 '12 at 22:40

Short answer: No, you don't have to worry about it. The viewfinder on cameras generally represents the actual frame captured by the camera.

I think it will really help as background to read a few of the questions and answers in the crop-factor tag. It's important to know where this term comes from and why it gets bandied about.

In any case, the viewfinder will be made to show you the actual field of view captured by the sensor. So, on a smaller-sensor camera, the viewfinder will be sized to match.

For practical reasons on cameras with a physical mirror, the finder may be a bit smaller — something like 95%. With live view or in mirrorless cameras, the electronic finder will show you the exact image to be captured. On a few rangefinder-style cameras like the Leica M9 or Fujifilm X Pro, the finder isn't through-the-lens, and is often actually larger (with "bright lines" drawn to represent selected narrower focal lengths). But that's not the case with a DSLR, and in any case has nothing to do with sensor size.

  • That the viewfinder/sensor design is the controlling factor is exactly what I was after. Thanks for that. Reading about crop factor is in fact what raised the question in my mind. Thanks all. This is really excellent help. I am certain I will be back with more questions.
    – John Works
    Dec 24 '12 at 22:45

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