So have I got DoF, length etc right?

[JohnN]

Hi,

Getting my head round comparative depth of field etc has taken a bit but is this basically it?

Comparison of 1.5 crop in part for ease.

Length: 100mm appears as 150mm
Depth of field: f1.4 appears as f2

However for light gathering (ie setting ISO or keeping faster shutter speeds) it is still a 1.4

Where I loose it a bit is compression, I think it is down to distance from subject, not apparent focal length, which if correct means that a crop can never produce the same image as a full frame as despite being able to match the bokeh the compression will still look the same.

Bah, it's not quite as easy as pressing a button is it?

 

[Phil V]

Hi,

Getting my head round comparative depth of field etc has taken a bit but is this basically it?

Comparison of 1.5 crop in part for ease.

Length: 100mm appears as 150mm
Depth of field: f1.4 appears as f2

However for light gathering (ie setting ISO or keeping faster shutter speeds) it is still a 1.4

Where I loose it a bit is compression, I think it is down to distance from subject, not apparent focal length, which if correct means that a crop can never produce the same image as a full frame as despite being able to match the bokeh the compression will still look the same.

Bah, it's not quite as easy as pressing a button is it?

You're right, but how significant is it anyway?

The image you produce is your image, no one is looking at it and comparing it with an image on a different system that doesn't exist.

Sometimes the phrase 'overthinking it' needs to be kept in mind.

 

[JohnN]

I totally agree and thank you.

The only time it matters is when trying to go for a certain look, for instance if I'm trying to get something close to my much loved 135L on Fuji say the closest I truly have is a Samyang 85mm f1.4, though of course theres a lot more too it to that, like how the bohek appears and contacts, sharpness and so on.

 

[Phil V]

That I understand a bit, I always shot portraits on 135mm on film, and shooting crop for years I loved the 85mm, but it never had quite the same magic. Since going full frame I've bought a 135L again and love it.

We all live somewhere on the scale between 'zoom with your feet' * and trying to recreate a specific feel, I'm probably closer to your view too, but we're stuck with the physics I'm afraid.

* too often said by people who really ought to know better, moving closer with a wide lens will never recreate the image from a longer lens, it's flipping mental advice.

 

[chris malcolm]

A crop sensor camera can't produce the same image as a full frame? Not even if I change the focal length to get the same angle of view, widen the aperture to get the same depth of field, and use a long enough exposure at a low enough ISO to get the same dynamic range?

 

[JohnN]

I don't believe so - the compression will still be off.

** stands back and watches the worms pour out of the can **

 

[ancient_mariner]

A crop sensor camera can't produce the same image as a full frame? Not even if I change the focal length to get the same angle of view, widen the aperture to get the same depth of field, and use a long enough exposure at a low enough ISO to get the same dynamic range?

Nor will FF produce the same results as medium format. Generally the best advice is to work with what you have until you know why it doesn't produce what you want - then source the appropriate kit that WILL produce it.

 

[woof woof]

Hi,

Getting my head round comparative depth of field etc has taken a bit but is this basically it?

Comparison of 1.5 crop in part for ease.

Length: 100mm appears as 150mm
Depth of field: f1.4 appears as f2

However for light gathering (ie setting ISO or keeping faster shutter speeds) it is still a 1.4

Where I loose it a bit is compression, I think it is down to distance from subject, not apparent focal length, which if correct means that a crop can never produce the same image as a full frame as despite being able to match the bokeh the compression will still look the same.

Bah, it's not quite as easy as pressing a button is it?

To make things easy I have MFT which is x2 crop and "FF" and if the apertures and focal lengths are selected for equivalence, for example MFT at 25mm and f4 and FF at 50mm and f8... the shots will be essentially identical. The depth of field will be the same, the camera to subject distances for the same framing will be the same, the compression will be the same, even the noise in the picture will (possibly) be very similar (as you'll possibly be using lower ISO's due to using wider apertures) and indeed the biggest differences may be any lens characteristics due to the design, shape of aperture blades etc... and the FF image will probably be sharper if you go pixel peeping.

In my experience the crop factor works and once you get into the mindset of applying the crop factor to focal length and aperture many things can be more or less equal

I don't believe so - the compression will still be off.

** stands back and watches the worms pour out of the can **

No, I don't think so. Compression is down to framing and camera to subject distance.

Stand x feet from your subject and shoot with a 300mm lens and you've got compression... but stand the same distance from the subject with an 8mm lens and crop the shot to give you the same framing as the 300mm shot and assuming you have the resolution (you wont but this is just a thought experiment) and the 8mm shot will give the same compression as the 300mm shot.

I did take some sample shots for someone and I posted them on this site, I could dig them out if anyone needs proof...

But... 25mm on MFT will give the same compression as 50mm on FF (and so will any other focal lengths adjusted for the format.) If the camera to subject distance is the same.

 

[JohnN]

That's interesting, I'll have a dig about when I'm home

 

[HoppyUK]

A crop sensor camera can't produce the same image as a full frame?

Yes, it can.

Not even if I change the focal length to get the same angle of view [and perspective], widen the aperture to get the same depth of field, and use a long enough exposure at a low enough ISO to get the same dynamic range?

And that would do it, pretty much an identical image.

There would still be minor differences to sharpness (because the smaller format needs to be enlarged more) and individual characteristics of optical design could subtly affect bokeh, such as a five-bladed aperture will render out of focus highlights slightly differently to nine blades, etc. Sensor performance could affect noise and dynamic range too, but those relative details aside, the images would be the same.