Make apsc behave like Fullframe with Lens

[Samuell]

Hello and good day to you!

Im not really new to Photographie but I'm getting serious about it now.

Im thinking of buying a FullFrame Camera but I dont know if its even worth it.

Im reseaching for days now and it is very hard since I find contredicting information floating around on the net.

Ok I understand the crop factor a 50mm is a 75mm on apsc (fov wise) good I just get a 35mm and that is taken care of. Now I think you have to adjust the aperature too so you get the same DoF f1.4 is probably a fast lens for FullFrame the DoF would be equilvent to 2.1 on my apsc camera while giving me the same exposure. No problem I just get a F0.95 and that would give me the same DoF as a f1.4 on Fullframe while beeing 1Stop brighter. Fullframe has better ISO performance maybe 2 Stops so I would gain 1 Stop of light If I go for

FullFrame 50mm f1.4 instead of

apsc 35mm f0.95

I know this is just one lens exaple and all this compansating isnt possible for most lenses Im just wondering If I understood It right. there is a cheap chinease lens 35mm f0.95 I was thinking of playing around wirh it but the money spend would probably be better spend just getting an a7 and a cheap vintage f1.4 50mm ? For same resaults with better dynamic range?

[Pieter]

You are mostly correct. For all practical purposes and intents, a 35mm f/0.95 lens on an APS-C camera will give the same depth of field and field of view as a 50mm f/1.4 on a fullframe camera. The ISO-performance of a fullframe camera is also only about 1 stop better than an APS-C camera with the same amount of megapixels.

So e.g. a FF-camera with a 50mm lens at f/1.4, 1/100 sec shutter speed and ISO800 produces roughly the same depth of field, field of view and noise performance as an APS-C camera with a 35mm lens at f/0.95, 1/100sec and ISO400.

However: the cheap 35mm lens will likely produce absolutely crap quality images at f/0.95. So unless you're into that 'arty dreamy look' of blurry images that are a hazy mess, your money is best invested elsewhere.

By the way, the new Laowa 33mm f/0.95 seems to be pretty good stopped down, but that wasn't your intent:

https://www.lenstip.com/index.php?test=obiektywu&test_ob=615

Edited September 25, 2021 by Pieter

[XKAES]

Samuell,

I'm not sure what your goal is -- fast lenses, DOF control, more ISO, less weight/smaller size, less expense, better quality, or what.  What do you currently have, and what do you want to achieve that you current can't?

[Samuell]

Was just wondering if you can turn an apsc camera into a FF with the right lens. Apparently you can/could if such lenses existed.

[XKAES]

If you are asking if you can put full-frame lenses on APS cameras -- SURE, but you don't get a full-frame image.  You get an APS-sized image.  The image will appear magnified because the APS sensor is only using a portion of the full-frame image created by the full-frame lens.

The APS sensor size is fixed and does not change by changing the lens.  If you have a quart of water, you don't end up with a gallon of water by pouring it into a gallon bucket.

Edited September 25, 2021 by XKAES

[Samuell]

I was just seeking validation for my calculations since I figuerd it out from multiple sources and had no one to ask If I was right. basically

Apsc f0.95 35mm 200iso = FF f1.4 50mm iso 400 

Or at least It would give you a similar pitcture FoV DoF and exposure wise.

Unless someone tells me diffrently....

looking to get a 7c now since its nice and small and I wont buy a cheap chinease lens just to compansate for the short commings of apsc specially the nerrow DoF wont be achivable with an apsc kamera since you can also put a f0.95 lens on a fullframe body that would mean you need a f0.7 for a similar DoF ( I think NASA was building those in the 60')

[XKAES]

As Pieter said, your computations are OK, but you won't get a higher resolution by simply switching to a full-frame lens -- since the sensor size stays the same.

If you are using a full-frame lens on an APS sensor, it's a good idea to determine what changes and by how much -- such as focal length, perspective, DOF, etc.

[Pieter]

It's also good to know that when using an APS-C camera, it doesn't matter if you put a FF 50mm lens on it or an APS-C 50mm lens: the resulting image is the same (DoF, FoV and exposure). Put both lenses on a FF camera and you'll see that the image with the APS-C lens vignettes heavily or has black edges around the image. The focal length is the same, but the area of the projected image is bigger with a lens designed for FF cameras.