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12-10-2019, 11:40 AM   #1
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Pentax K1 mark ii and crop sensor lenses

Hello!

I have been shooting Pentax for years and just upgraded to my first full frame: the K1 mark ii. I realized today that I didn't even stop to think about how my current lenses would work on it. My "Sigma 18-50mm F/2.8-4.5 DC OS HSM" has strong black vignetting around the photos I take with it. So does my 50 - 135 mm (can't find my order to get the specs). I now understand that these lenses are for crop sensors. :-(

I also have these lenses:

Pentax smc DA 50mm f/1.8 Lens (crop sensor lens)

SMC Pentax-M 1:1.4 50mm (full frame sensor lens)

Now I am planning to sell the two zoom lenses. What about my 50mm 1.8, which is for crop sensors? Will the photos I take with that be just as if I'm taking photos with a crop sensor camera?

Thanks for any help and encouragement you can provide.

Audrey

12-10-2019, 11:42 AM   #2
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Full Frame Coverage of DA Lenses: Comprehensive Test - Gear Guides | PentaxForums.com

This summarizes tests of da lenses on full frame.
12-10-2019, 11:45 AM   #3
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I use the 50mm F1.8 on my K1 and it works well, don't notice any vignetting. I also have the FA50mmF1.4 and actually I prefer the DA-L 50
12-10-2019, 11:57 AM   #4
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QuoteOriginally posted by audreyanne Quote
What about my 50mm 1.8, which is for crop sensors? Will the photos I take with that be just as if I'm taking photos with a crop sensor camera?
The short answer is that the camera will detect the DA 50/1.8 as a crop sensor lens by default and will apply a crop to APS-C dimensions to yield a capture at 4800px x 3200px (15.36Mpx). That being said, one can override the crop sensor designation and shoot to the full frame. Many users are quite happy with the results from such, though some might say there is vignette and poor corner/edge performance. I would give it a try with blank wall to test for vignette and a textured wall for corner/edge detail; or perhaps simply shoot with it and see if it delivers on a par with your Pentax-M 50/1.4 at shared apertures.


Steve

12-10-2019, 01:53 PM   #5
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Thank you so much, all of you, for helping me out! The link was very helpful, too! :-)))
12-10-2019, 08:22 PM   #6
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Try the square crop mode on the K1-ii with your APS-C lenses.
12-10-2019, 08:35 PM   #7
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QuoteOriginally posted by beachboy2 Quote
Try the square crop mode on the K1-ii with your APS-C lenses.
3200 x 3200px (10 Mpx) ?


Steve
12-10-2019, 08:56 PM   #8
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QuoteOriginally posted by stevebrot Quote
3200 x 3200px (10 Mpx) ?
I think the camera set to FF mode + APS-C lens + square crop will trim away a lot of the vignette sometimes seen using crop lenses. And leave 4912 x 4912 pixels, or 24 MP.

12-10-2019, 09:37 PM   #9
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QuoteOriginally posted by rawr Quote
I think the camera set to FF mode + APS-C lens + square crop will trim away a lot of the vignette sometimes seen using crop lenses. And leave 4912 x 4912 pixels, or 24 MP.
OK...got the gist of it and would provide similar to native APS-C performance with most crop-sensor lenses, though with a significantly narrower diagonal FOV than either format the same focal length FF lens using the full frame.*


Steve

(...I guess it is pretty obvious who does not have a K-1, eh? )

* 34mm for a square crop from FF vs. 28.4mm for APS-C and 43.2mm for 24x36mm FF

Last edited by stevebrot; 12-12-2019 at 08:22 PM.
12-10-2019, 09:38 PM   #10
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It would be nice if Pentax could enable a 4:3 or 16:9 format in the K-1, like they have done with the square format.
12-12-2019, 06:15 PM   #11
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It’s hard for me to comment, because even though I short crop sensor cameras from 2003 (*istD ) through 2018 (K5D) until I got my K1MKII last Christmas’s, all of my pleases except fork the sigma 10-20 and my Samyang 8mm fisheye are full frame lenses.

Before I got the 10-20 I shot with the FA J 18-35 on my PZ1 for wide angle shots. I was always conscious of buying lenses that could cover full frame.

I ultimately believed that either using my film bodies or a Ff DSLR, I should consider using and buying FF lenses when ever possible
12-12-2019, 08:21 PM   #12
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QuoteOriginally posted by audreyanne Quote
Hello!

I have been shooting Pentax for years and just upgraded to my first full frame: the K1 mark ii. I realized today that I didn't even stop to think about how my current lenses would work on it. My "Sigma 18-50mm F/2.8-4.5 DC OS HSM" has strong black vignetting around the photos I take with it. So does my 50 - 135 mm (can't find my order to get the specs). I now understand that these lenses are for crop sensors. :-(

I also have these lenses:

Pentax smc DA 50mm f/1.8 Lens (crop sensor lens)

SMC Pentax-M 1:1.4 50mm (full frame sensor lens)

Now I am planning to sell the two zoom lenses. What about my 50mm 1.8, which is for crop sensors? Will the photos I take with that be just as if I'm taking photos with a crop sensor camera?

Thanks for any help and encouragement you can provide.

Audrey
Depends on what particular uses to which you are looking in order to get which gains by getting the K-1 II.

What I am getting at is this. If it were me, i would probably sell the Sigma short zoom, and get a suitable short zoom for the K-1 II. The DFA 28-105 would be on my short list. It has a very useful zoom range, very highly-rated performance, and offers fine WR construction, yet is modest in size, weight, and cost. If you need the f/2.8 aperture, then it would be the DFA 24-70mm lens, likewise fine performance but costlier and somewhat larger and heavier, yet not too bad. But for me, since I have and am very fond of the DA* 50-135mm f/2.8 tele lens, and I would chafe at carrying the very large and much heavier DFA 70-200mm f/2.8 instead to do the same job, I would either get a KP for such use and keep the DA* lens for doing the same work with the KP, or simply use the DA* lens with the K-1 II in crop mode. This in crop mode would provide quality similar to having the DA* lens on a K-5 IIs body- but with yet lower noise and better high ISO performance, not too shabby!

Getting a KP at todays prices would likely be less or at no more cost than than going for the larger DFA 70-200mm, even after selling the DA* lens to carry the heavier DFA 70-200mm, which is also very costly.

I would consider getting the HD FA 35mm f/2 for a marvelous light-weight general-use versatile walk-around prime lens for the K-1 II body. It s also not very costly. Keep the DA 50mm f/1.8 lens for now, as on an APS-C body or in crop mode with the K-1 II it is a very good FL for portrait work, and can produce quality imaging.

note; I hope you understand that the focal length 50-135mm on APS-C format cameras (or crop mode on the K-1 II) yields a field-of-view (FOV) in the frame similar to what you'd see in the frame with a 70-200mm lens designed for FF use installed on the K-1 II body that is not set to crop mode.

Last edited by mikesbike; 12-12-2019 at 08:54 PM.
12-13-2019, 11:25 AM   #13
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Hello all! Thanks for your help! I am writing because I have a similar but related problem. A lens I just ordered from KEH that is supposed to work with a Pentax full frame camera is the Tamron 28-75mm f/2.8, autofocus. When I put this lens on my Pentax K1 Mark ii, it says "F--" error on the display, as if the camera is not communicating with the lens. I am so disappointing. The camera won't take a picture. Do you know why? Thanks!
12-13-2019, 11:35 AM   #14
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QuoteOriginally posted by audreyanne Quote
Hello all! Thanks for your help! I am writing because I have a similar but related problem. A lens I just ordered from KEH that is supposed to work with a Pentax full frame camera is the Tamron 28-75mm f/2.8, autofocus. When I put this lens on my Pentax K1 Mark ii, it says "F--" error on the display, as if the camera is not communicating with the lens. I am so disappointing. The camera won't take a picture. Do you know why? Thanks!
Has the lens got an aperture ring? If so, set it to 'A' and that should solve your problem

That's the short simple answer, for the long complicate answer see this:
https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/110658-...x-dslrs-f.html
12-13-2019, 11:36 AM   #15
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Yep that fixed it! I set it to enable using the aperture ring. Even the auto focus works now. Thanks so much!!! :-))))) You made my day!
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