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01-16-2014, 07:34 AM   #1
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K30-Rokinon 14mm wide angle-

I'm confused :/ I have a few questions.
I have a Rokinon 14mm wide angle, I have attached pictures. (sorry, low quality cell phone pics)
Once the lens is attached and I turn my camera on it asks me "input focal length"...I assume that is 14 but there is no option for 14. Am I wrong? If I am wrong what exactly is it asking for and if I am right then what exactly do I choose? I usually just go with 12 but why is there no 14 option.

Also, I have an Aperture ring on this lens that I just discovered I could rotate (I know big DUH!). So I rotated it from the 22 it has always been on since I got it and have used it many times to 2.8. (rotated it when it was not attached to body) Since I have done that I get F-- in my aperture block. I have tried off and on, reattaching lens, switching modes and I get the same result. What's going on?

Also, when it was working I noticed I cannot use AF Active area select, actually I cannot auto focus at all, I get nothing if I half press doesn't matter which focus I have it on. Is something wrong or is this the way it is with this lens?

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01-16-2014, 08:22 AM   #2
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QuoteOriginally posted by itiswhatitis Quote
Once the lens is attached and I turn my camera on it asks me "input focal length"...I assume that is 14 but there is no option for 14. Am I wrong? If I am wrong what exactly is it asking for and if I am right then what exactly do I choose? I usually just go with 12 but why is there no 14 option.
Yes, you input 12mm. You are supposed to put in 14mm, but the camera doesn't allow that option, so its better to put in a slightly lower than higher (so the SR undercorrects, rather than overcorrects)

QuoteOriginally posted by itiswhatitis Quote
Also, I have an Aperture ring on this lens that I just discovered I could rotate (I know big DUH!). So I rotated it from the 22 it has always been on since I got it and have used it many times to 2.8. (rotated it when it was not attached to body) Since I have done that I get F-- in my aperture block. I have tried off and on, reattaching lens, switching modes and I get the same result. What's going on?
Ok, go to Camera menu, to the end of it and Enable the Aperture Ring Use. Thing is, in M mode, the camera will stop down the lens to the number selected on the aperture ring. And if you want to meter, you have to press the green button. If you have auto ISO or any other mode, it will turn to Av with continuous metering, but it will always shoot wide open (at f2.8).
But! This lens has an A setting. So you want to press the little knob on the aperture ring, and turn it to A and leave it there. In a mode, the aperture will be displayed and controlled by the camera (so you don't have to do it by hand).

This lens does not have autofocus. The best you can do is Catch in focus aka focus trapping. But no AF, the lens doens't have the mechanism. Its a mostly manual lens, only automation it has is the aperture in A mode.
01-16-2014, 09:25 AM   #3
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Just to be clear, you should press the button next to the f/22 and rotate the ring over to the "A" position; it will click in. Otherwise it will work only as an "M" lens requiring you to press the green button to stop down to the chosen setting (and you lose the EXIF f-stop data).

Non-AF lenses do not allow you to do focus confirmation other than in the center of the frame. You have to focus in the center and then recompose the shot. You are likely to find that using live view can be more accurate. Not only can you move the focus confirmation to your desired location, pressing the OK button allows you to magnify the focus point for more-precise focusing.
01-16-2014, 11:08 AM   #4
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Regarding focusing on that lens - the Samyang/Rokinon 14mm f2.8 often has a miscalibrated distance scales, so 2m is not actually 2m. But luckily it is an ultra-wide, so if you shoot f8-f14 you get a very big depth of field if you focus around 2-3m.
If you shoot above f11 the image quality might suffer due to diffraction, so the photos won't be as nicely sharp. That lens definitely takes some getting used to, there is a learning curve, but it will be fine once you figure it out

01-16-2014, 11:39 AM   #5
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QuoteOriginally posted by itiswhatitis Quote
but why is there no 14 option
Because Pentax has never made a lens at that focal length. Strange, but true. As noted above, set your camera at 12mm and enjoy!!!


Steve
01-16-2014, 11:40 AM   #6
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I have the lens on the way at this time. Based on my Samyang experiences with the 85mm and especially the 8mm, the likely culprit is focus shift (which has been reported, but not all that well documented as to its extent). On a lens this wide that doesn't focus very close I doubt the problem comes into play much. However, the apparent lack of proper calibration (wide open) might simply be a matter that the designers want the lens to achieve infinity focus at all f/stops (a reasonable expectation). Based on what I have read, the lens achieves maximum resolution by f/5.6 (unlike most ultra-wides that require f/8 or f/11 to achieve corner sharpness). I guess you could go up to f/11 if you want to achieve blur (waterfalls, etc.) in bright lighting.
01-16-2014, 11:50 AM   #7
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QuoteOriginally posted by stevebrot Quote
Because Pentax has never made a lens at that focal length. Strange, but true. As noted above, set your camera at 12mm and enjoy!!!


Steve
I agree that 12mm would be the best setting - under-compensate every time with zooms and odd lens lengths. Some folks say that if you are shooting at a relatively fast shutter speed (for this lens anything above about 1/50th is going to be easily hand held), you are better off just turning off the anti-shake mechanism. I suspect that is good advice.

Just to be clear, Pentax has a current 14mm lens...

By the way, the Q allows you to dial in the exact lens length - very nice feature. Also, review on the Q allows you to cycle through the various screen views by just hitting the info button repeatedly (image only, standard info, histogram, full setting info with small image) - rather than bringing up the menu to choose (who came up with that lame protocol?). Would love to have a firmware update to take care of those two niggles.
01-17-2014, 12:29 PM   #8
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Yep, here is the Pentax 14mm. Its just the way the "input focal length" window was implemented at that time. Hopefully all newer cameras will have it the same way the Q does. This is definitely one of those little things that.. could and should be improved by Pentax. Nothing you or I can do at the moment, though, other than maybe write emails to Pentax

01-17-2014, 12:58 PM   #9
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Weird question here: I was under the impression that the input focal length did not do anything for the SR, but was for the EXIF data only?

David
01-17-2014, 01:02 PM   #10
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QuoteOriginally posted by David&karen Quote
Weird question here: I was under the impression that the input focal length did not do anything for the SR, but was for the EXIF data only? David
Nope. SR will "shake" (or rather, move to compensate) differently depending on the focal length, because different focal lengths will "show" a different amount of blur for the same amount of camera shake. A 300mm lens will seem very shaky when in the same hands (and same shutter speed), a 14mm might seem completely stable. Exif is actually the secondary function.
In fact, if you have SR disabled, the camera might not even ask you the focal length and leave that part of the exif data empty.
01-17-2014, 04:59 PM   #11
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Thank you for all your help! I bought this lens for real estate photography, does a decent job, but I wanted to get to know it a little better and see what it can do.
Your replies are much appreciated!
01-17-2014, 05:47 PM   #12
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QuoteOriginally posted by ScooterMaxi Jim Quote
I have the lens on the way at this time. Based on my Samyang experiences with the 85mm and especially the 8mm, the likely culprit is focus shift (which has been reported, but not all that well documented as to its extent). On a lens this wide that doesn't focus very close I doubt the problem comes into play much. However, the apparent lack of proper calibration (wide open) might simply be a matter that the designers want the lens to achieve infinity focus at all f/stops (a reasonable expectation).
Just to add my experiences with this lens, focus shift is quite strong on my copy, and does need compensating for if you want the best from your images. The main shift is from f2.8 to f4. Anything after that is negligible. It's quite predictable though, so you learn how much of a turn it needs after focusing wide open. Another technique I use when using any aperture other than f2.8 is to set the camera to f4, hold depth of field preview down, focus, and then stop down to working aperture to make the exposure. Seems to work pretty well.

I'm not sure that the distance scale calibration issue is related to the focus shift issue though if I'm understanding you correctly there. On my copy the calibration is absolutely way off whether you're wide open or not. The infinity mark is around an inch and a quarter away from where it should be for f2.8 on the barrel. At f4 it's even further away.

Luckily the lens makes up for these shortcomings by its generally superb optics, though do check the focal plane is aligned properly when you get it - I sent two copies back before getting a good one!
01-17-2014, 08:44 PM   #13
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Wide open is different on the K-30

Hi Jonby,

Thank you for the S/R/B etc. 14mm background. Looks like the lens will be here Tuesday (holiday is slowing it down).

My concern is working primarily off of my 8mm experience where, frankly, after extensive testing I have crusaded against those who insist on physically altering the focus distance that at (the very soft) wide open setting focuses on infinity at 2 meters. By f/11 the focus scale as set at factory is dead accurate. So, if you make the "correction" at wide open all those sharper, stopped down settings fail to achieve infinity! Obviously, stopping down to achieve focus is very helpful on that lens; note that this is the opposite of the usual kind of focus shift commonly found on fast, long lenses (including the Samyang 85 - but not nearly so dramatically). I suspect that the shift on the 14mm is similar to the 8mm - that is allowing you to focus much closer as you stop down the lens (minimum focus is about 16 inches wide open on the 8mm, but only about an inch away from the lens surface by the time you reach f/11).

As an owner of the K-30 and K-01, I have discovered a very odd situation differentiating the two cameras regarding focus and metering wide open with fast lenses. On the K-30, the camera always sets the aperture to f/4 on faster lenses when metering is activated (LV or otherwise). You can override to a more open setting if you activate an optical stop-down function (or in some instances that is stop-up!). On the K-01 (which is always LV of course), the faster lenses stay wide open unless of course you trigger the stop-down mechanism. For quite some time, I was thinking that live view focus peaking using my 85 f/1.4 was considerably superior on the K-01 and wondering how on Earth that could be the case. Well, the three stop difference on the K-30 screen darn well should make quite some difference! I have no idea why the implementation is different. The pondering around the K-30 has been bright light requires sensor preservation (seems reasonable). But why not the same for the K-01?

Last edited by ScooterMaxi Jim; 01-17-2014 at 08:51 PM.
01-18-2014, 11:55 AM   #14
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QuoteOriginally posted by itiswhatitis Quote
Thank you for all your help! I bought this lens for real estate photography, does a decent job, but I wanted to get to know it a little better and see what it can do. Your replies are much appreciated!
For that I suggest you use a nice heavy tripod and 2 sec timer. And the 2 sec timer automatically disables SR btw. On DSLRs it also opens the mirror 2 sec before it opens the shutter, so there is fewer vibrations in the camera body. This is essentially the best IQ you can get. And for bonus points, cover the viewfinder so light can't enter from that direction. And as some have stated, you might want to set up the camera buttons such that you have access to the DoF preview.
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