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View Full Version : Using camera crop factor to get two focal length from one lens?



Elliotj3d
08-04-2015, 06:15 AM
Is it possible to get two focal length from one lens on my bmpcc? So for instance with a MTB SPEEDBOSTER on my 16mm I have a 27mm equivalent, take it off and put a dumb adapter on ill get a 47mm equiv. ?

Having two focal lengths with one lens, possible or just stupid?

DPStewart
08-04-2015, 07:36 AM
Not stupid at all.
That's exactly how it works!
Of course, without the speedbooster you'll need that 1-stop more of light that the speedbooster was giving you - but other than that you do indeed get 2 different focal lengths from your lenses.

Elliotj3d
08-04-2015, 08:37 AM
Anyone used the Rokinon 16mm before? Would it be better than say a 24mm Rokinon?

Denny Smith
08-04-2015, 11:02 AM
You do not really get two different focal lengths from the lens, it is still a 16mm lens. You do, however, get two different angles of view, one wider than the other, corresponding to an equivalent angle of view a 27mm and 47mm on a FF camera.
Cheers

DPStewart
08-04-2015, 12:18 PM
Anyone used the Rokinon 16mm before? Would it be better than say a 24mm Rokinon?

The 16mm is a great place to start. Especially if you do outdoor shooting and need a wide view.

The 24mm would make a great second lens to add to that as it's going to bring you in tighter like a portrait lens.

Elliotj3d
08-05-2015, 03:46 AM
The 16mm is a great place to start. Especially if you do outdoor shooting and need a wide view.

The 24mm would make a great second lens to add to that as it's going to bring you in tighter like a portrait lens.


As I like to shoot wide, my 16 would be the workhorse, for the mean time I think i will probably hire the 24mm.

Denny Smith
08-05-2015, 05:48 PM
The Veydra 16mm mini prime is excellent on the pocket camera, smaller than the Rok/Sam and sharper too. Comes native MFT mount, so no adapters required. This is my favorite lens on the pocket, along with my Zeiss ZF 28mm.

LochnessDigital
08-05-2015, 09:13 PM
The Veydra 16mm mini prime is excellent on the pocket camera, smaller than the Rok/Sam and sharper too. Comes native MFT mount, so no adapters required. This is my favorite lens on the pocket, along with my Zeiss ZF 28mm.

As an owner of the Veydra set, I can attest to their quality.

That said, I don't think the Veydra 16mm on the pocket is nearly wide enough for the OP's "workhorse" of a wide lens. The 12mm will be a great option but it isn't out yet.

The Rokinon 16mm + a focal reducer should be about about 11mm. Cheaper than the Veydra even if you go for the Speedbooster and significantly cheaper if you go for the RJ. I would expect the image quality on the Veydra to be superior, but the focal reducer allows you to stop down to a similar aperture as T2.2 on the Veydra. At that point it's probably a washout. Of course, you don't just pay for the Veydra in optical performance, it has lots of mechanical advantages over the Rokinons.

All that being said, since the OP asked about making one lens more versatile, if I were to go for the Speedbooster route, it would be the .58x version with a Sigma 18-35 f/1.8. One lens can cover 10mm-35mm with 10-20mm of that range being in the f/1.0 area. Shallower depth of field if you need it. Low light if you need it. Super versatile.

For my style of shooting though, it's much less run-and-gun. I like to methodically choose my lenses and the Veydras are exactly that. Looking forward to the release of the 12mm.