Trouble understanding lenses

Discussion in 'Photography Beginners' Forum' started by Taylorl813, Oct 6, 2018.

  1. Taylorl813

    Taylorl813 TPF Noob!

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    Hey guys, I'm having some trouble understanding crop vs full frame cameras, or at least I think I finally understand, but need some confirmation.

    Are pictures taken with a D3200 APS-C camera cropped 1.5x regardless of the lens being DX?

    Does that mean that a picture taken on my Nikon d3200, with my Nikon 35mm 1.8 dx prime, will look roughly the same as a photo taken with a 50mm FX lens on a full frame camera? (Obviously with less detail.)

    Thank you,



    - Taylor


     
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  2. dennybeall

    dennybeall No longer a newbie, moving up!

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    Why would there be less detail. An FX camera and a DX camera take the same photos and if the zoom lenses are adjusted to the same field of view, say 50mm, then you would be hard pressed to see the difference. If you had difficult conditions, say poor light, then the FX may win the duel.
    Unless you're a pro facing difficult conditions or needing to play "machine gun", like the photographers at the House Hearings, you don't need an FX camera.
    Stand Clear now as the flames are coming...............................
     
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  3. n614cd

    n614cd TPF Noob!

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    The answer is it depends.
    If you have a lens which matches the sensor. To 50mm shots matching the same field of view will look very similar.
    If however you use the same exact lens on both sensors; then yes you have to multiply up the lens for the crop sensor.

    Sent from my SM-J737T using Tapatalk
     
  4. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    In terms of field of view only, yes, they will be similar.



    Well,...... maybe,....... maybe not.
     
  5. Braineack

    Braineack Been spending a lot of time on here!

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    yes.

    no.



    put the same lens on a DX and FX and the image circle the lens projects onto the sensor is identical. but, on sensor is smaller than the other, so you're only capturing a portion of the projection.

    crude drawing:

    upload_2018-10-6_10-30-46.png
     
  6. photo1x1.com

    photo1x1.com TPF Supporters Supporting Member

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    Maybe these two images will help you. I just recently did a shooting to compare various focal lengths and apertures on full frame and crop sensor.
    Yes, pictures taken with a crop sensor camera (D3200) will be cropped 1.5x by regardless whether you use a DX lens or a full frame lens.
    cropVsFullFrame1.jpg cropVsFullFrame2.jpg
     
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  7. Designer

    Designer Been spending a lot of time on here!

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    I see by your questions that you don't have a firm grasp of the concept. Please do a search on here (all forums) for discussions about the "crop factor". There are some very good threads and posts (including excellent graphic illustrations) which may help you to understand.

    I think to properly understand the concept and to put certain "internet misconceptions" out of your head, you would do well to start at the beginning.

    Waaaay back in time photographers would make photographs on glass plates, which were NEVER as small as what we currently call "full frame". These glass plates were commonly 8x10, and until roll film came along most photographers used fairly large formats. They could make contact prints 8x10, or even larger if their camera took glass plates that were larger.

    Then, we got 35mm roll film (which was used in the motion picture industry) , and some manufacturers made cameras that would take this new roll film. These cameras (35mm) were called MINIATURE cameras, because, well, they were MUCH SMALLER than the old wooden view cameras in common use in that time. These little cameras (full frame, remember) were a huge success with hobbyists, reporters, and even sometimes professional photographers, because the film was cheap, the cameras were smaller and lighter, and easy to use.

    With digital technology in its infancy, manufacturers could make sensors larger, but the high cost ($$$$) put the price of cameras ($$$) out of the reach of most consumers ($), so they made their sensors smaller, so they could sell more cameras at a reasonable price ($). Some professional photographers wanted cameras with sensors the same size as their old film cameras, so manufacturers made cameras with sensors that were about the same size as the old 35mm film, and the photographers were happy, but they had to pay more ($$$) for their "full frame" cameras.

    Now to get even MORE people to buy cameras, manufacturers came out with even SMALLER sensors, which made just as good image captures, but were cheaper to produce, so more people could afford them. This led to many different sizes of sensors for people to start talking about, so the internet stepped in with much commentary, and that is how the term "crop factor" came into widespread use, even though many people had no idea what that really meant, in terms of what came out the other end.

    So then photography help forums tried to explain it, but sometimes failed, so now we have more than a few neophytes becoming confused, as they try to prefigure the field of view that their camera was going to capture when changing lenses from DX to FX and vice-versa.

    "You mean I've got to do some math?" "Well, which way do I multiply to get it right?" "What happens if I mount a (DX/FX) lens to my "crop sensor" camera?" "How do I know if I'm doing it right?"

    To ease your mind a bit, I will offer this:

    What you see is what you get.
     
    Last edited: Oct 6, 2018
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  8. Braineack

    Braineack Been spending a lot of time on here!

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    i should expand my crude drawing to the difference of a DX lens, since you brought it up:

    upload_2018-10-6_11-44-49.png
     
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  9. Dave442

    Dave442 No longer a newbie, moving up!

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    From what the others have posted, you can see a decent sketch from Braineack showing the difference between using a 50mm lens on a FF and then that same 50mm on a crop sensor camera (DX). Then Photo1x1 shows a good comparison of the 50mm on FF and the 35mm on DX. The one thing you will notice in the images posted by Photo1x1 is the greater depth-of-field (DOF) produced by the images made using the 35mm lens on the DX body vs the 50mm lens on the FF body. The 35mm lens when set to the same f-stop as the the 50mm lens will have a smaller lens opening - creating greater depth-of-field.

    From Braineack's second sketch you can see that if you put the DX lens on a FF camera the image circle projected will not cover the full size of the sensor. The advantage of the DX lens is that the glass and overall lens size is smaller than a similar FF lens for the same focal length.

    You have a DX camera, DX and FX lenses will work just the same on that camera. The D3200 camera does require lenses with built-in focus motors for the auto-focus to work (there area lot of older Nikon lenses that do not have the built-in focus motor).
     
  10. greybeard

    greybeard Been spending a lot of time on here!

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    You are pretty much on track with how DX and FX work. The difference in detail is not as obvious as is when you change formats with film. With film if you were to compare 35mm to 110 not only are you starting with a smaller image from the lense but a smaller negative on the film. With digital, you are starting with a smaller image from the lense but, the image on the sensor is converted to a digital description of the image and then sent to a computer in the camera where the numbers are recorded to the card then converts it to a analog image you can see on the monitor. Even though it is a smaller sensor it may have the same number of pixels as the full frame sensor and so theoretically it could have the same level of detail if the lense on the DX is up to it. The difference between DX and FX is not so much fine detail but how they reproduce high ISO and how they can recover shadow detail. In my experience, FX has about a 2 stop advantage over DX but, DX is getting better with every generation. My 1st serious digital camera was a Sony D8. It was an 8 mp with a Zeiss zoom. At ISO 100 it was descent but at ISO 400 it was so-so and at ISO 800 it was down right terrible. Today my Nikon D7500 does quite well at ISO 6400 but not as well as my D750. However, if you compare images from the D7500 and D750 with comparable lenses at ISO 100, they are tough to tell apart.
     
    Last edited: Oct 7, 2018
  11. ac12

    ac12 No longer a newbie, moving up!

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    This "crop factor" has a FF format sensor as the reference. But WHY?
    In the old days, no one talked about a crop factor for 35mm film or MF or 4x5. My 35mm film camera was not a 3x crop factor camera. So why should I as a DX shooter have to think in terms of a FF format? DX is just a smaller format to FX, as 35mm film was a smaller format to 4x5 film. The crop factor tells me how much smaller the DX sensor is compared to a FF sensor, but for that that is about it.

    Interestingly, I have not seen a reverse crop or multiplication factor for the larger MF sensors, only the sensor dimension in mm. Nor do the MF sensors reference their sensors as crop sensors. Because as far as I know, there is no full frame (56x56mm) MF sensor to reference to.

    As a DX shooter, one thing that you want/need to do is, think in DX format.
    The DX normal lens is 35mm, and everything should reference from there.
    I use a magnification concept, that gets me away from the confusing "FF equivalent."
    So for DX:
    • A 17mm lens is a 0.5x lens.
    • The 35mm normal lens is a 1x lens.
    • A 70mm lens is a 2x lens.
    • A 150mm lens is a 4.3x lens, round to 4x.
    • A 300mm lens is a 8.6x lens, round to 9x.
    For comparison, for FX:
    • A 24mm lens is a 0.5x lens.
    • The 50mm normal lens is a 1x lens.
    • A 100mm lens is a 2x lens.
    • A 200mm lens is a 4x lens.
    If you want to get technical, you can use the actual sensor diagonal for the normal lens. But then the math gets harder to do in your head, as it isn't a nice round number.

    When I shoot 6x6, I don't go from FF to 6x6.
    80mm is my 6x6 normal lens, and everything references from there.
    My 150mm lens is a 1.9x lens, or round to 2x.

    In your case, FX or DX lens on the DX camera, does not matter. The only thing that matters is focal length.
    A 35mm DX lens and a 35mm FX lens will give you the same image.

    As talked about and illustrated by others above, you can use a FX lens on your DX camera.
    In fact most of my lenses are FX or older 35mm film lenses. I only have 2 DX lenses.
     
  12. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    Simple. The vast majority of camera users when digital first came out were using 35mm cameras. Most were hobbyists, parents recording their children growing up, taking vacation photos etc. Very few ventured into medium format, let alone large. Many carried, at most, a 3-lens kit. 35mm, 50mm and 135mm. And they knew, when looking at a scene, which lens would work best.

    Since 'crop' sensors were first to market because 'full-frame' sensors (the same physical dimensions of 35mm film images) would be too expensive, the manufacturers 'invented' the crop-factor conversion to better assist those hordes of 35mm-film shooters 'adjust' to the smaller format.

    I say it's time to deposit 'the conversion factor' to the dustbin of history. Let it reside the Hall of Useless Technology, next to ice picks, buggy whips and 8-track tapes.
     

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