what does the x1.5 mean ?? I was advised when I got my camera that my sensor is x1.5 meaning if I got a 50mm lens, it would be more closer than what it would be on a FF.
1.5 is the Crop-Factor; ie the number you have to multiply the lens' focal length by, to get an 'equivalence' to the focal-length lens that would give the same
angle of view on a 35mm film camera (or 'full-frame' widgetal)
Maths time! - The focal length lens that gives the 'normal' angle-of-view, is 'approximately' the diagonal length of the 'frame'.
The standard frame size for a 35mm film camera is 24x36mm. Do some Pythagoras on that, and remembering my 1st Year Maths Teacher's joke about the Red-Indian Chief arguing his one fat wife was worth two of any others, "The Squaw on the Hippopotamus, is the sum of the Squaw's on the other two hides"... The Diagonal is the square root of 24^2+36^2 = 43.266mm.....
NOW; Thing is, that the film frame isn't square, its oblong... so that notional 'normal' is a bit nebulous....there is an argument, that the 'normal angle' lens length aught to 'really' be taken as the hypotenuse of the square of the longest side of the film frame... so on a 35mm film trap, that would be 36mm squared, doubled and rooted; which for 35mm film, comes out at.... 50.9mm... hence the 50mm 'standard' lens length of a 35mm SLR, not 44mm.. because you are merely chopping a strip off the square, top and bottom, to make it an oblong.
Which begs mention of the Helios 44.... a favoured lens amongst the adaptor brigade, it's badged as a 44, and shipped as the 'standard' lens with Zenit 35mm SLR's, like the 50mm on most of its peers, BUT... it's actually a 58mm focal length lens!!! BECAUSE!!! 44mm is the strict, diagonal of a 24x36mm film trap; 50mm the diagonal of the square of the longest side, BUT..... 58mm.... is actually a 'little' closer to what we 'perceive' 'cos our peripheral vision isn't as good as our central vision!
Like I said, its all a little nebulous; and as so much in photography, the strict 'science' is perverted by practicality....
BUT.... essentially, a Nikon APS-C digital camera, has a film-trap, or sensor, 16x24mm, half the size of the 35mm film-trap, of 24x36mm... and a bit more maths!
If you work the diagonals; for the 'full-frame' sensor, 24x36mm, it works out at 44mm or 50mm on the longest side.
If you work the diagonals; for the 'APS-C' sensor, 16x24mm, it works out at 22mm or 35mm on the longest side.
The ratio between 35mm and 50mm is 1.428... close enough 1.5.... and a dimensionless unit, a pure 'factor' because if you divide 50mm by 35mm the mm cancel each other out, and you are left with a pure number without units...
SO, if you take that 'Factor' its a convenience, you can now use to multiply any focal length by, to get an 'equivalence' for the
angle-of-view to another lens of another focal length, when used on the alternative format camera.
What the salesman said, when you bought the camera, and what you understood by what he said, is probably something rather more nebulous, with more than a little repetition distortion adding to the confoundement! BUT... that's essentially it. You have an APS-C sized sensor, and the 'Crop-Factor' for quick equivalence to the
angle of view of a lens on a 35mm or Full-Frame camera, is 1.5x the focal length. A lens of any focal length is still that focal length, and your APS-C sized sensor is still an APS-C sized sensor, half the area and capturing half the photons of a 'full-frame' sized sensor.
So, put a 50mm lens on your camera, its still a 50mm lens; the camera still has an APS-C sized sensor. but, the ANGLE OF VIEW, and it is limited ONLY to that angle of view, is now the 'equivalent' of a 75mm lens, used on a full-frame or 35mm film camera.
As to it being more closer... err... well, that's another topic! You get more 'zoom' effect, as if you were closer to the subject, but, opens up a much larger can of worms, that does!!! IF you were actually closer to the subject... being closer would make that subject larger in the frame.... but you have shortened the subject range, so everything would be closer to the camera and larger in the frame.... and you'd get less in it. Which is where it starts getting perverse...
If you 'actually' got closer to the subject, you would need a wider angle lens to get the same effective framing; now the wider angle lens, would have a shorter focal length, and its closest focus distance would be nearer the camera, its hyper-focal distance would also be closer to the camera, and the range of 'critical' focus between the two, would tend to be a lot shorter. So the Depth-of-Field, you got, would tend to be greater, and the focus fade before and after your subject, would be compressed into that shorter subject range, and the 'perspective' altered.
WHICH, is one of the reasons, that there's no substitute for alternative lenses 'really', and why the idea of 'zooming with your feet' or get close by getting close, is another bit of nebulation.... as said, a lens is a lens is a lens, it don't know or care what size frame is behind it, and these 'equivalences' only work in pretty specific situations and for pretty specific properties.
As its a common, and fairly pertinent topic, I'll mention the 'shallow focus' effects you can get with longer focal length lenses.
If you are used to a micro-sensor camera, like a compact or bridge or camera-phone; these very small sensors beg very short focal length lenses, to give something in the 'normal' angle range. The lens on my Aldi action-cam is just 4.5mm. Coincidentally I actually have a 4.5mm fish-eye for my DSLR. That 4.5mm lens, on the action-cam, gives something around the 50Deg region, 'Angle-of-View'; on the Fish-Eye, its delivering a full 180 Degree 'Full-Circle' angle of view... it actually makes a circular image, with 180Deg AoV side to side and top to bottom, in the middle of the oblong frame of the photo. Now, the action-cam would get the same image projected on it's sensor, BUT that sensor is so small, it's actually only recording the very middle of the picture; ie it has an enormous 'crop-factor', because its cropping an enormous amount off the top, bottom and edges of the image its given.
Now; that 4.5mm focal length lens, has such a short focal length, that its closest focus distance is almost nothing! In fact, I can almost put the front element up against 'something' and it appears in focus in the picture! More; the range of 'critical-focus', from there to 'hyperfocal' where everything is effectively in focus, is also incredibly short and close to the camera; a phenomena exploited by camera makers, pushing ever smaller sensor cameras, because that very near closest focus distance and incredibly short zone of critical focus, means that they probably don't actually NEED to make a focus mechanism to cover it; the lens can be set at the factory at the Hyperfocal range, and to all practical purposes, the camera is then 'Focus Free'; you will never have a subject so close to the camera that it will fall into that fuzzy zone of critical focus where it's necessary, certainly if they use a more moderate aperture, that would tend to give a larger Depth-of-Field around the focus range.
SO, its only when you step up to larger sensor cameras, that beg longer focal length-lenses, that you might actually start to 'see' these shallow focus effects, where the subject range is inside that of the 'critical-focus' zone of the lens.
Now, this begs the 'wow' factor of seeing shallow focus effects, and leads many to look for more of it from very fast aperture lenses. Usual one for APS-C Nikon, is the AF-S 35 f1.8, which has the equivalent angle of view to a 50mm on an old 35mm film SLR, where single digit f-number lenses, similarly were derigeur.... again, oft chasing these shallow-focus effects, with the 'smaller' format cameras and much shorter focal length lenses than were 'normal' on larger 'Medium-Format' film cameras, they competed against in the enthusiast arena.
Thing IS, that those shallow focus effects are mainly function of the camera to subject distance, and with the larger format camera the longer focal length lens tends to have a much further closest focus distance, and a much longer range of critical focus beyond it, up until Hyperfocal.
Now... working in that much extended critical-focus range, much more often, you would get shallow-focus effects, at much more moderate apertures, and you would get a 'focus fade; infront and behind your subject, within the limits of that critical focus zone. Use a shorter lens on a smaller format camera, with that much closer close focus distance, shorter and closer range of critical focus, and you are likely to not get such a shallow focus effect without using a lower f-no, and more, the focus fade still only extends between the close focus, and hyper-focal distances, so the degree of fade tends to be a lot more pronounced or 'sharper'... and resultant images can, especially from an APS-C sensor camera, start to look quite 'fake', the degree of focus dissociation between the subject and back-ground so 'sharp' the subject appears as though they have been cut and pasted in photo-shop into the scene, rather than a part of it..... BUT, its only when you step up from a micro-sensor camera that you get any of it at all, and it sends many folk chasing ever faster aperture lenses and contemplating the amount of 'Bokah' they are getting... rather than necessarily the quality of it! But still.
Point is, that this sort of illustrates how the 'Crop-Factor' ONLY works on making comparison of the Angle-of-View between the focal length of lenses used on different formats. The different lens lengths have different closest focus distances, and Hyperfocal distances and zone of critical focus between the two, and how far into that zone of critical focus you may be, determines the perspective of the image, as well as the focus and focus fade effects you get, and the 'Crop-Factor' does NOT work here, and a longer lens does NOT 'get you closer' to the subject! It just generates an image 'sort' of like you had been, the subject, magnified a bit in relation to the frame.
Like I said, photography is riddled with anomaly where the strict science is perverted by practicality, and resultant nebulisms where the real question is "Does it really matter?" and that is very circumstance dependent!