Crop sensor shooting advice ... Please!

[Redgums]

I'm working through some videos on Youtube and have decided to replicate what they are doing. Problem is, they are all using full-frame cameras and I have a Nikon DX (1.5 cf).

If we look at the 50mm portrait exercises, I have a magnification factor of 1.5x.

Am I correct in my thoughts that using a 35mm (Giving me a 50mm FOV equivalent) will not give the same result as the 50mm on a full frame owing to the different lens design?

Should I simply move 30% further away?

thanks.

[ricktas]

Moving 30% further way sounds simple in principle, but aperture and depth of field is dependant on several factors, one of which is distance to subject. So say you set your camera to f8 and the subject is 1 metre away, if you then move to 1.35 metres from the subject, your depth of field is altered. Depth of field, being the distance, front to back that is in focus.

You can try it here: http://www.dofmaster.com/dofjs.html

Using a different lens, will give you an equivalent field of view, but other factors do come into play, again.

Why not just use what you have and experiment and learn from what happens. After all that is how we all learn about how to improve our photography, we try things, see what they do, and remember what does what, for future shoots. If we just copied what someone else does, all we end up doing is making copies, from instructions, and not really learning a lot along the way. Experiment, fail, experiment, succeed, is not a bad thing.

[ameerat42]

I'm working through some videos on Youtube and have decided to replicate what they are doing. Problem is, they are all using full-frame cameras and I have a Nikon DX (1.5 cf).

If we look at the 50mm portrait exercises, I have a magnification factor of 1.5x.

Am I correct in my thoughts that using a 35mm (Giving me a 50mm FOV equivalent) will not give the same result as the 50mm on a full frame owing to the different lens design?

Should I simply move 30% further away?

thanks.

It's not easily 100% repeatable between the two systems.

1) Moving the extra distance will NOT do it, but will just change the perspective. You'd have to be at the same distance for that in
both cases. So...

2) Definitely go with the equivalent FOV lens - you said 35mm is the equivalent. BUT then...

3) Get the same aperture as they used in the 50mm lens to get the same DOF. Use aperture = focal length ÷ f-stop
The aperture primarily controls the width of the "bundles of light rays" striking the sensor, BUT note that the apparent effect will differ somewhat by the fact that
the "throw" of the "bundles" between the lens and sensor is usually different between the two systems. You may have to experiment a bit here.

4) Apply a measure of good luck.

Am.

[Redgums]

Thanks, guys! I was planning to experiment anyway, but I think I should just buy a FF!

now to convince SWMBO!

[ameerat42]

But iffyer don't give it a try and tell us we'll NEVER know

[arthurking83]

Thanks, guys! I was planning to experiment anyway, but I think I should just buy a FF!

That's the best part

... now to convince SWMBO!

That's the hard part!

On a more serious note tho:

1. the magnification factor is zero! (EDIT: was pulled up on this. Mag factor is not zero, it's actually 1(ie. no increase))
The actual term is the crop factor. Using a 50mm lens on a 135 format full frame sensor give the exact same magnification factor as does using the exact same 50mm lens on an APS-C sensor camera.

Lens(and focus distance) determines magnification factor.
Sensor size doesn't.

There are two real life flaws with doing comparisons between full frame and crop cameras and various focal lengths and focal length factorising(is that even a word? )
In easier to understand terms, if you want to try to mimic say a 50mm lens at f/2 on a full frame camera with a similar and factorised FOV and DOF rendering using a 35mm f/1.4 on an APS-C camera, while the image may look very similarly rendered, the simple fact that you are using two distinctly different lenses here is where the major difference will be.
Different lenses render differently.
In some comparisons it may be a huge variance, in other comparisons it may not be so noticeable, but it will be there.

The overall and basic consequence of all this is simply:

Get the lens you think you will use more often! .. it really is that simple.

The most common advice I give some folks is something like this.
Get a simple and useful zoom lens of reasonable quality and competence.(in Nikon terms one of my faves is the cheap lil 18-105mm lens.
It has a decent zoom range, and apart from a few very minor flaws, it's quite good and handy to have in some situations.

After a bit of time shooting with it, you would have a decent sample size of different images that can help you determine your next best lens to get.
With some simple and free software, you can do an analysis of those images to determine which focal length you use most often.

So for an 18-105mm lens, you may find that you shoot more at 24mm than you even bothered to check the first time around. check for the type of images you shot at 24mm. If they are portrait types then:
Why bother with either a 50mm or 35mm lens for portraits if you find that most of the portrait images you shot were at 24mm!

Hope this makes sense.

ps. the software I can refer you to do this analysis is called Wega. (actually and more accurately Wega 2).