Hi I own a Nikon D3300 and bought the Nikon 50mm 1.8g lens which I love. I'm confused though. I've been really trying to get my head around the difference between DX and full frame camera and know that there is some sort of crop factor on a DX. Does that mean that my 50mm 1.8g is working like and 85mm on my DX camera? Can someone help me to understand! Thanks Gayle
and the site receives a small commission
Beginner 50mm 1.8g lens on a DX camera body is it like an 85mm?
- Thread starter Frances23
- Start date
- Messages
- 2,868
- Name
- Chris
- Edit My Images
- Yes
You will have the same field of view with your 50mm on your camera as you would with a 75mm on a FF camera.
B
BrynBoru
Guest
I have always understood that relative aperture is also affected. If you want to think of a DX lens in 35mm film terms you say it has an equivalent focal length of 1.5x the actual focal length because of the narrower FOV when using the smaller sensor. By the same token you should apply the same 1.5x factor to the aperture because of the effect on depth of field. Therefore if you are applying the crop factor to the focal length you need to apply it to the aperture also. Maybe this video helps, or maybe others will argue differently.
Last edited by a moderator:
- Messages
- 2,771
- Name
- Graham
- Edit My Images
- Yes
If you're considering the maximum aperture in terms of DOF then yes, this is why I specified light gathering properties.I have always understood that relative aperture is also affected. If you want to think of a DX lens in 35mm film terms you say it has an equivalent focal length of 1.5x the actual focal length because of the narrower FOV when using the smaller sensor. By the same token you should apply the same 1.5x factor to the aperture because of the effect on depth of field. Therefore if you are applying the crop factor to the focal length you need to apply it to the aperture also. Maybe this video helps, or maybe others will argue differently.
View: https://www.youtube.com/watch?v=f5zN6NVx-hY
- Messages
- 4,906
- Name
- Simon
- Edit My Images
- No
The relative field of view / aperture thing kind of makes sense but if you try to take it to its logical conclusion it gets confusing.
Try this instead... if you take a 50mm lens off a full frame camera and put it on a crop sensor camera then the only thing which has changed is the sensor size. You have the same DoF as that 50mm lens on a full frame camera, the same light gathering capability, the same perspective, the same compression and the same perspective distortion*. You just get less of the scene in the frame.
Multiplying the focal length and f number by 1.5 to give you the approximate focal length and aperture sort of works - but only approximately.
*An aside - the perspective distortion tends to be less noticeable on a crop sensor as it's more apparent at the edges of the frame - which you've just cropped.
Try this instead... if you take a 50mm lens off a full frame camera and put it on a crop sensor camera then the only thing which has changed is the sensor size. You have the same DoF as that 50mm lens on a full frame camera, the same light gathering capability, the same perspective, the same compression and the same perspective distortion*. You just get less of the scene in the frame.
Multiplying the focal length and f number by 1.5 to give you the approximate focal length and aperture sort of works - but only approximately.
*An aside - the perspective distortion tends to be less noticeable on a crop sensor as it's more apparent at the edges of the frame - which you've just cropped.
DG Phototraining
Woof
- Messages
- 5,064
- Name
- Dave
- Edit My Images
- Yes
No
See Juggler's explanation for why
An 85 mm works like an 85mm on a DX though
Dave
- Messages
- 23,200
- Name
- Richard
- Edit My Images
- No
No, depth-of-field will change. But since DoF does not exist as a measurable entity before the image is a) output at a certain size, and b) viewed from a certain distance, you can't say whether it has increased or decreased without outlining all the relevant parameters.
But either way it will not have changed massively, by about one stop, and may even pass unnoticed. Not something for a newcomer to worry about IMO.
Crop factor works exactly for calculating equivalent fields of view and effective f/numbers for DoF.
Perspective is a function of camera to subject distance, nothing else. Using words like distortion in relation to perspective, is not right - I prefer exaggerated or flattened perspective, as appropriate. Lens distortion is something different.
woof woof
I like a nice Chianti
- Messages
- 39,615
- Name
- Alan
- Edit My Images
- No
I know what you mean but I do disagree with this way of saying it.
The DoF you will perceive at any image size and / or viewing distance is set by the camera and lens type and settings, distance to subject, what is in the frame and where it is in the frame etc. Once you've stood at a certain point, set the selected gear up, pointed the gear at something and pressed the button the result you will see at whatever output size and viewing distance you choose is set and inevitable and at least to a degree predictable. It does however take experience to be able to get near predicting what the final result will be. I'd rather pick my gear, settings and shooting circumstance with some idea of what the final result will be in mind than believe that a fundamental characteristic of the shot does not exist as a measurable entity before its output and viewing.
To me we must start at the final image size and how it will be viewed and work back from there. If we can do that at least to a degree whilst the DoF may not be exactly measurable before output and viewing we should be able to get somewhere near to predicting it, perhaps if not exactly then near enough to stop ourselves being disappointed. This should be the case for any format once we've got to grips with it or can relate it to something we're familiar with by using crop factors and incorporating them into our decisions.
I know I'm nit picking but the view that DoF doesn't exist before the output size and viewing distance are set just doesn't sit well with me. To me the DoF we will see at whatever output size and viewing distance we intend is set when we stand there and press the button so it's best to base our decisions on the final output and viewing and base our selection of gear and settings on the result we want and those results should be pretty predictable.
- Messages
- 23,200
- Name
- Richard
- Edit My Images
- No
You shouldn't disagree because we're saying the same thing. Please read what Juggler said and my reply carefully - he said 'you have the same DoF' and that is wrong. But I did not say DoF doesn't exist at the moment of capture, I said that it 'doesn't exist as a measureable entity' until all the relevant parameters are applied. When sensor format is changed, DoF is still 'set' at the moment of capture and easy to calculate, but the results will be different.
I know you know this Alan, but for those that are puzzled by this, depth-of-field is all about magnification. When sensor size is reduced, the image must be magnified more when output for viewing. The change in magnification alters the perceived DoF.
woof woof
I like a nice Chianti
- Messages
- 39,615
- Name
- Alan
- Edit My Images
- No
I know. Did you not read my post?
I know what you mean but as I said I disagree with saying that DoF doesn't exist before you output and view and I also disagree with saying that it's all about magnification... for many people much of the time, and before you jump on that I'll explain further at the end of this post.But for now, Yes I know the theory and I know the practice but I do think that posts on forums confuse the issue and to me saying stuff like DoF doesn't exist until you display and view the image is just misleading. Of course it exists and what you'll see at whatever image size and viewing distance you choose is set by your choice of gear and settings and we should with experience be able to predict what we're going to get even when using a different format. All we need to know is the crop factor in relation to something that we're familiar with and once we know that it should be easy to predict the results. For example when switching from MFT to FF and back again as I do the results DoF wise are never a surprise to me.
When I read this stuff on line and much less often talk to people about it I find the confusion easy to understand as some people haven't used different format sizes or spent time comparing the results or are perhaps just confused by the IMO overly confusing and convoluted discussions on the internet. This really shouldn't be hard or confusing and IMO it's just made so unnecessarily by over technical discussion.
And on to my problem with saying it's all about magnification. Yes, you are right but in the real world I don't think it's that much of an issue most of the time. For example suppose I walk out the door with my FF camera and my x2 crop camera and take two pictures of the same subject from the same point as follows...
Shot one - FF camera with a 50mm lens at f8 and at a reasonable ISO setting that isn't going to affect the image quality.
Shot two - x2 crop camera with a 25mm lens at f4, ditto the reasonable ISO.
Substitute whatever focal lengths and apertures you want, just apply the crop factor.
If I then display the pictures on the sort of computer, tablet, phone or TV that people usually have about the house or print the pictures out at about the same size, not mega big but lets say at any size up to maybe A4 (portrait or landscape, I don't care and I don't care about one being 3:2 and the other being 4:3 either) or even a bit bigger and then look at the pictures normally or even quite closely no one is going to look at the pictures and say "It's obvious which is the shot from the x2 crop camera as the extra magnification has made the DoF and the CoC and general IQ differences easy to spot." That's just not going to happen. Only on the internet in discussions about format sizes and DoF
IMO you're only going to see obvious differences if you print really big or start excessively pixel peeping at very high magnification.In the real world (and this is just my opinion) if you take the crop factor into consideration and adjust your settings accordingly there will be a sharpness advantage to the FF shot if you look closely enough but DoF wise and CoC wise I just don't believe that anything will jump out at you. The character of the bokeh and the shape of the aperture blades might but these are characteristics of the lens and not a result of the format size or anything to do with DoF or magnification in this context. And in the real world I've never heard anyone talking about circles of confusion and when explaining this to anyone I wouldn't even stress it
Yes, magnification matters but keep within anything like the normal and reasonable boundaries that normal people keep mostly between and magnification might not be an issue at all.IMO talking about magnification in anything other than very simple terms is just confusing and IMO there's usually no need to even mention COC. All that's needed is to point out the simple concept that enlarging a picture more degrades quality if viewing from the same distance and as smaller formats need to be magnified more image degradation will occur sooner.
I went through all this years ago with film and later with digital I compared APS-C to FF and then MFT to both and it was an expensive process but worth doing as once I'd done it I decided none of it was a real world issue for me.
The only time I've had to think about display size, viewing distance and visible detail was years ago when producing BIG pictures for display on stage and obviously people at both the front and the back of the audience needed to be able to see enough detail but other than that I've never ever found that I needed to think about this stuff and especially about circles of confusion. This stuff is IMO irrelevant to most people most of the time
whole image wise at least, cropping and displaying big is another thing and should prompt more thought.Anyway, sorry for the intrusion
woof woof
I like a nice Chianti
- Messages
- 39,615
- Name
- Alan
- Edit My Images
- No
Hope you get to grips with it
- Messages
- 1,024
- Name
- Tom
- Edit My Images
- Yes
No
See Juggler's explanation for why
An 85 mm works like an 85mm on a DX though
Dave
Sorry to drag this back into the open (and rather here than in a new thread!). Would a full frame 50mm lens (I’m looking at the nikkor AF-S 50mm f/1.8G) be the same on my D3300 as the kits lens (18-55mm) at 50mm? Or would it be like 75mm DX lens?
-Oy-
Worzel Gummidge
- Messages
- 9,050
- Name
- Dave
- Edit My Images
- No
The same.