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11-29-2017, 12:02 PM   #1
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Pentax K1 and 50 mm F1.8 Da lens

I would like to know if the 50 mm F1.8 Da lens covers the full frame sensor of the Pentax K1 camera.

I've read that it does , however, I would love to hear it from someone on the forum who can actually verify this information.
Does it change the resolution /megapixels of the image?

11-29-2017, 12:27 PM   #2
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According to these reviews it does work on FF SMC Pentax-DA 50mm F1.8 Reviews - DA Prime Lenses - Pentax Lens Reviews & Lens Database. Resolution/megapixels will be the same as any other 50mm lens on the K-1. Proviso being that some lenses have more resolving powers than others.

In built lens correction features will only work in crop mode however.
11-29-2017, 12:47 PM   #3
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QuoteOriginally posted by giselag Quote
I would like to know if the 50 mm F1.8 Da lens covers the full frame sensor of the Pentax K1 camera.

I've read that it does , however, I would love to hear it from someone on the forum who can actually verify this information.
Does it change the resolution /megapixels of the image?
As long as you disable crop mode you'll get a full frame image from it. There's more vignetting wide-open than dedicated full frame 50's, but the DA lens is still pretty hard to beat for the price, IMO.

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11-29-2017, 01:03 PM   #4
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QuoteOriginally posted by giselag Quote
I would like to know if the 50 mm F1.8 Da lens covers the full frame sensor of the Pentax K1 camera.

I've read that it does , however, I would love to hear it from someone on the forum who can actually verify this information.
Does it change the resolution /megapixels of the image?
Works great -- just a bit of vignetting wide open

11-29-2017, 02:44 PM - 1 Like   #5
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Here are some actual shots I took a few minutes ago, with the DA 1.8 mounted on my K1.

I shot a uniformly illuminated (natural daylight from a big picture window) piece of white foam core. The images have been downsized to 1/8 size in photoshop elements, which should not affect the lighting variation across the frame.

The vignetting is quite obvious at f1.8, but from f4 on, there is some but not a lot, and it's pretty much the same at all apertures. Note that the overall exposure is a bit variable. If you import these into photoshop with a histogram window activated, you can see the tail to the dark side and how it varies from frame to frame. If you play with levels (CNTL-L), you can exaggerate the effects.

Also, clearly, somebody needs to clean his sensor!!
Attached Images
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PENTAX K-1  Photo 
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PENTAX K-1  Photo 
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PENTAX K-1  Photo 
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PENTAX K-1  Photo 
11-29-2017, 03:09 PM   #6
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Vignetting will also change with focal distance - in the lenses I have tested it is usually worst at infinity.
Some images showing image quality in the edges would also be useful.

I suspect there are reasons it is not rated as FF, while the DA*200 and DA*300 are. Mind you, I am perfectly happy with the DA*55 on full frame, even though the image circle doesn't quite make it in certain circumstances.
11-29-2017, 05:17 PM - 1 Like   #7
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QuoteOriginally posted by Sandy Hancock Quote
Vignetting will also change with focal distance - in the lenses I have tested it is usually worst at infinity.
The reason for this is that the exit pupil of the lens is closest to the sensor at Infinity, at shorter focus distances the exit pupil moves further away* from the sensor.

* Certain lenses with Internal focusing groups or lenses with a fixed exit pupil/floating elements will generally exhibit less variation of vignetting across the focusing range.
11-29-2017, 06:57 PM   #8
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Thank you for all the information and samples. If you have sample portrait shots with the K1 and the 50mm DA f1.8 lens, I would love to see a few.

11-29-2017, 09:25 PM   #9
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QuoteOriginally posted by giselag Quote
Thank you for all the information and samples. If you have sample portrait shots with the K1 and the 50mm DA f1.8 lens, I would love to see a few.
I think Giselag, people with the money to buy a K-1 have got better lenses than the DA50, so you likely won't get many samples.

But I've found it works fine, and probably vignettes less than the FA31 wide open.

Read here:

Pentax DA 50mm work well on K1 ? - PentaxForums.com
11-29-2017, 11:57 PM - 1 Like   #10
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QuoteOriginally posted by clackers Quote
I think Giselag, people with the money to buy a K-1 have got better lenses than the DA50, so you likely won't get many samples.
You underestimate the pull of LBA!
11-30-2017, 12:00 AM - 1 Like   #11
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Some samples, shot in FF-mode:

nifty fifty | Flickr
11-30-2017, 12:22 AM   #12
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Comparable FF primes like the Sony FE 50mm f1.8 seem to vignette more than the DA 50 f1.8:


From the Lenstip review of the Sony 50mm f1.8

And when tested on APS-C [before the K-1 came on scene] by Lenstip, the DA 50 f1.8 revealed itself to be the just about the lowest vignetting 50 f1.8 they had tested.

I don't think I'd worry too much about the DA 50 f1.8. Most similar lenses will probably do no better in terms of vignetting on FF.

Last edited by rawr; 11-30-2017 at 01:39 PM.
11-30-2017, 03:21 AM   #13
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QuoteOriginally posted by rawr Quote
FF mode, the DA 50f1.8 looks to vignette less than comparable FF primes like the Sony FE 50mm f1.8 when tested on a A7RII
Well that is embarrassing for sony.
11-30-2017, 04:35 AM   #14
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Even the Zeiss 50mm Planar f1.4 has a full eV of vignetting in the corners, according to Imaging-Resource.

This is the world of full frame.
11-30-2017, 09:13 AM - 3 Likes   #15
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Here's a few taken with the K-1 and 50mm f/1.8
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PENTAX K-1  Photo 
View Picture EXIF
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Last edited by enoeske; 11-30-2017 at 01:02 PM.
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