[hadi]

I looked around and cant seem to find the answer.
So the question is that i recently got the rokinon 14mm lens and it seems to work just fine. However, when compared to my other full frame lenses, something seems off (to me).

I currently have the pentax 50mm 1.4, the pentax 24-70 2.8, the pentax 100mm 2.8, thr tamron 70-200mm 2.8, and the rokinon 85mm 1.4. All those lenses have one thing in common which is that they are all full frame lenses, and as such, the back element/glass (the part that goes into the camera) is pretty big when i compare it to my 18-55 kit lens, or even the 18-135mm lens.

I accounted that for apsc lenses vs full frame.

Yet the rokinon 14mm lens has the same back element as the 18-55mm and the 18-135mm lens.

Is that normal? Did i get a lemon?

I also noticed that between the 24mm and the 14mm, sure the difference is there, but its not as much as i expected when i compared my 18mm apsc lens to the sigma 10-20mm.

When i put it in crop mode, the lens obviously crops the field of view as expected.

Wondering if i got something wrong.

Now, mind you, ive only had the lens for 1 day...

[Na Horuk]

Is that normal? Did i get a lemon?

Um, what? Do you think it can happen that somehow a lens gets a wrong LENS ELEMENT? Come on. Its possible that a lens element is slightly misaligned, by a matter of milimeters. but there is no way they would just give you a straight up wrong lens piece lol The only "problem" would be if you accidentally bought/received a Samyang 16mm (which is a crop-only lens). Just read the labels on the box and lens. The size of the back element can indicate the format (APSC, FF, MF), but it is not a definitive rule. It depends on the lens design
Anyway, I recommend you post sample photos.
The Sigma at 10mm on APSC is almost as wide as the 14mm on FF. Nothing unusual there, since the "crop factor" is around 1.5. But the Samyang will give you better aperture (lets you get more shallow DoF, more light) and sharper image. My Samyang 14mm is really sharp at f2.8 already, and stays amazing up to f10 or so, but I only have APSC camera.

Now, mind you, ive only had the lens for 1 day...

I think its just this Its first day nervousness, happens with any major purchase. Use the lens, take photos, have fun. After a couple days, after some comparisons, then tell us how things go. Post some sample photos if you want.
Just push the little button on the aperture ring and lock the ring into A mode. This will give you lots of automation on the camera, so you can use P or Av mode. Next, learn how to focus. I had quite a bit of difficulty with this at first, but then I learned the distance scales are miscalibrated. There are some posts and youtube videos about how to calibrate it yourself. I didn't bother with that, I just learned at which number I can get hyperfocal focusing at f8.

I'm sure you will enjoy the lens, just give it some time.

[hadi]

Um, what? Do you think it can happen that somehow a lens gets a wrong LENS ELEMENT? Come on. Its possible that a lens element is slightly misaligned, by a matter of milimeters. but there is no way they would just give you a straight up wrong lens piece lol The only "problem" would be if you accidentally bought/received a Samyang 16mm (which is a crop-only lens). Just read the labels on the box and lens. The size of the back element can indicate the format (APSC, FF, MF), but it is not a definitive rule. It depends on the lens design
Anyway, I recommend you post sample photos.
The Sigma at 10mm on APSC is almost as wide as the 14mm on FF. Nothing unusual there, since the "crop factor" is around 1.5. But the Samyang will give you better aperture (lets you get more shallow DoF, more light) and sharper image. My Samyang 14mm is really sharp at f2.8 already, and stays amazing up to f10 or so, but I only have APSC camera.


I think its just this Its first day nervousness, happens with any major purchase. Use the lens, take photos, have fun. After a couple days, after some comparisons, then tell us how things go. Post some sample photos if you want.
Just push the little button on the aperture ring and lock the ring into A mode. This will give you lots of automation on the camera, so you can use P or Av mode. Next, learn how to focus. I had quite a bit of difficulty with this at first, but then I learned the distance scales are miscalibrated. There are some posts and youtube videos about how to calibrate it yourself. I didn't bother with that, I just learned at which number I can get hyperfocal focusing at f8.

I'm sure you will enjoy the lens, just give it some time.

thanks for the reply and clearing things up.
the box isn't really a good indication, as the first box i got said 'pentax k mount' yet it was also saying 'micro 4 thirds'. when i pulled it out of the lens, it was indeed a micro lens and not the k mount lens.

thats why i'm also a lil nervous. but it seems to be working just fine so far.

the focusing thing isn't too bad on my end during the day. i'm finding that most things are in focus after about 10 feet, even at f2.8.

i may have difficulty at night, but lets see

[Wingincamera]

I like the lens, but have not used it on a full frame camera. One thing I want to add is buy it from a good dealer because some have misaligned lens. I purchased mine from B&H and the first one was misaligned, I was able to return it for a quick replacement and the second one was perfect.

[mattt]

Format of the camera has nothing to do with it. Aperture is related to the focal length.

An 85mm f2 has a rear element that should accommodate passing light through a 43mm wide aperture.

An 14mm f2 would have an rear element that should accommodate light passing through an aperture of just 7mm wide.

For your 18-55 zoom you have a MAX opening that is f3.5 on the wide end (or three and one half aperture openings layed side by side by side would reach 18mm) At 55mm that same max aperture would fit 5.6 times in the focal lenght.

Abstract way to think about what that opening in the back of the lens does, but there you go. The back side of my SMC Pentax FA 35mm f2 vs my SMC Pentax 35mm f3.5 is pretty dramatic..

[clackers]

I like the lens, but have not used it on a full frame camera. One thing I want to add is buy it from a good dealer because some have misaligned lens. I purchased mine from B&H and the first one was misaligned, I was able to return it for a quick replacement and the second one was perfect.

It's great on the K-1.


Always send back a decentred copy, you're the consumer, insist on your right of exchange.

[Lowell Goudge]

I have the vivitar version of the 14 mm, and have used it on my PZ1. It gives great results, yes it is full frame, and no you cannot draw any conclusions about image circle and rear element size. Different lens designers do different things. Look at how small, for example the tamron adaptall 24 and 28 mm lens rear elements are , yet they are full frame.

What I can tell you is that the 14 mm has an appreciable amount of barrel distortion, and as a result depending on how tightly you crop the field of view can change quite a bit compared to some other better corrected lenses