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07-23-2016, 12:33 AM - 1 Like   #1
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K-1 lens challenge: 28mm

I am celebrating my first weekend with the brand new K-1 by performing a 28mm challenge. The challenge simply involved the use of 28mm lenses at my disposal with the following variables:

- a standard nondescript scene with near, medium and far field objects
- f-stop 6.3 (I selected this as it seemed a nice f stop for landscape photography)
- shutter time of 1/160th (exposure was checked)
- ISO 100
- tripod
- SR OFF
- photos taken within 15 minutes to eliminate time differences
- photos taken at 1:30 pm
- no hood use ('naked' 28mm photography)
- camera and lens shielded from direct light by verandah awning
- Used live view to focus the lens correctly

The lenses used in order of appearance were:

Pentax FA 28mm f2.8
Pentax F 28mm f2.8
Pentax A 28mm f2
Pentax M 28mm f2.8 (late model = Pentax A 28mm f2.8)
Pentax M 28mm f2.8 (early model)
Pentax K 28mm f3.5
Pentax K 28mm f2
Vivitar 28mm f1.9
Pentax M 24-50mm f4
Tokina ATX 28-85mm
Tokina ATX Pro II 28-70mm

Images were NOT post processed. Images are the camera JPGs with no alteration.

Each image obtained is listed below in an individual post. I haven't even looked at these images before posting so I have no idea what they look like.

Comments welcome.

---------- Post added 07-23-16 at 05:46 PM ----------

Pentax FA 28mm f2.8



https://www.flickr.com/photos/108842693@N02/28487652065/in/dateposted-public/

---------- Post added 07-23-16 at 05:48 PM ----------

Pentax F 28mm f2.8



https://www.flickr.com/photos/108842693@N02/27871970143/in/dateposted-public/

---------- Post added 07-23-16 at 05:50 PM ----------

[/COLOR]Pentax A 28mm f2



https://www.flickr.com/photos/108842693@N02/27871025794/in/dateposted-public/

---------- Post added 07-23-16 at 05:53 PM ----------

[/COLOR]Pentax M 28mm f2.8 (late model = A version)



https://www.flickr.com/photos/108842693@N02/27870988694/in/dateposted-public/



---------- Post added 07-23-16 at 05:56 PM ----------

Pentax M 28mm f2.8 (early model)



https://www.flickr.com/photos/108842693@N02/27870956524/in/dateposted-public/

Pentax K 28mm f3.5



https://www.flickr.com/photos/108842693@N02/28204220270/in/dateposted-public/

Pentax K 28mm f2



https://www.flickr.com/photos/108842693@N02/28204220270/in/dateposted-public/

Vivitar 28mm 1.9



https://www.flickr.com/photos/108842693@N02/28409017661/in/dateposted-public/

Pentax 24-50mm



https://www.flickr.com/photos/108842693@N02/28382174212/in/dateposted-public/

Tokina ATX 28-85mm



https://www.flickr.com/photos/108842693@N02/28382125272/in/dateposted-public/

Tokina ATX 28-70mm Pro II



https://www.flickr.com/photos/108842693@N02/28487271455/in/dateposted-public/

Some file size stats to aid discussion

Pentax FA 28mm f2.8 18.5MB
Pentax F 28mm f2.8 18.2MB
Pentax A 28mm f2 19.9MB
Pentax M 28mm f2.8 (late model = Pentax A 28mm f2.8) 17.9MB
Pentax M 28mm f2.8 (early model) 19.6MB
Pentax K 28mm f3.5 22.3MB
Pentax K 28mm f2 22.8MB
Vivitar 28mm f1.9 21.6MB
Pentax M 24-50mm f4 20.0MB
Tokina ATX 28-85mm 19.7MB
Tokina ATX Pro II 28-70mm 19.6MB


Last edited by Wild Mark; 07-23-2016 at 02:29 AM.
07-23-2016, 01:38 AM   #2
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Thanks for the effort.

Can you share full sized samples?

On Flickr perhaps?
Even though there may be compression with Flickr, since its applied on all samples, it can at least give an idea of edge sharpness.

I've found that on FF (or maybe its digital FF) that f8 is often not enough to give good edges and often f11 or between f8-11 is needed.
07-23-2016, 01:40 AM   #3
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I can only try

---------- Post added 07-23-16 at 06:41 PM ----------

Will update post when I have uploaded on Flickr

---------- Post added 07-23-16 at 06:43 PM ----------

QuoteOriginally posted by pinholecam Quote
I've found that on FF (or maybe its digital FF) that f8 is often not enough to give good edges and often f11 or between f8-11 is needed.
Thanks for the intel on this. I chose f6.3 with some reason. I wanted to see where failings might be evident in the lenses and it has proved to be the case.
07-23-2016, 01:51 AM   #4
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QuoteOriginally posted by Wild Mark Quote
I can only try

---------- Post added 07-23-16 at 06:41 PM ----------

Will update post when I have uploaded on Flickr

---------- Post added 07-23-16 at 06:43 PM ----------



Thanks for the intel on this. I chose f6.3 with some reason. I wanted to see where failings might be evident in the lenses and it has proved to be the case.
No prob.
Don't go thru the trouble of redoing anything unless you want to.
I know how tiresome it can be shooting such comparisons and putting them up.


Also, field curvature....
Quite the killer of many lenses at infinity distances while it can be totally fine for nearer focus subjects and scenes (or ones with foreground )

07-23-2016, 01:54 AM   #5
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Uploading now. All good.

Yes, the little standardised test has informed me a little on the lenses. I wont say anything now as I will wait for others to comment.

---------- Post added 07-23-16 at 07:30 PM ----------

OK updated original post with Flickr links to view more closely
07-23-2016, 04:53 AM   #6
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I'd be curious about the files sizes of the SOOC JPGs. Given that all the photos are of the same scene (except for the comings and goings of white & red cars), at the same ISO, any differences in file size are likely due to differences in the amount of fine detail captured with that lens.
07-23-2016, 04:59 AM   #7
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QuoteOriginally posted by photoptimist Quote
I'd be curious about the files sizes of the SOOC JPGs.
Good question

Pentax FA 28mm f2.8 = 18.5MB
Pentax F 28mm f2.8 = 18.2MB
Pentax A 28mm f2 = 19.9MB
Pentax M 28mm f2.8 (late model = Pentax A 28mm f2.8) = 17.9MB
Pentax M 28mm f2.8 (early model) = 19.6MB
Pentax K 28mm f3.5 = 22.3MB
Pentax K 28mm f2 = 22.8MB
Vivitar 28mm f1.9 = 21.6MB
Pentax M 24-50mm f4 = 20.0MB
Tokina ATX 28-85mm = 19.7MB
Tokina ATX Pro II 28-70mm = 19.6MB
07-23-2016, 06:08 AM   #8
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I wish you could get the new 28 -105 in the test.

07-23-2016, 06:12 AM   #9
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QuoteOriginally posted by sibyrnes Quote
I wish you could get the new 28 -105 in the test.
You have just reminded me. I could have done the FA28-105mm - bummer
07-23-2016, 10:41 AM   #10
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Perhaps I am biased since I have one, but I like the look of the F 28 2.8 slightly better than the other Pentax 28 mm lenses. I do realize the lighting may have changed somewhat while you cycled through all of the lenses and also the red car in the last two pictures changed the look of the scene. Overall, I am glad to see the F 28 mm 2.8 did as well as it did. I have had mine for 28 years now.
07-23-2016, 02:59 PM   #11
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QuoteOriginally posted by jddwoods Quote
Perhaps I am biased since I have one, but I like the look of the F 28 2.8 slightly better than the other Pentax 28 mm lenses. I do realize the lighting may have changed somewhat while you cycled through all of the lenses and also the red car in the last two pictures changed the look of the scene. Overall, I am glad to see the F 28 mm 2.8 did as well as it did. I have had mine for 28 years now.
Yes it performed very well. Distortion and CA was not as well controlled in that lens as say the A28/2 or K28/2 but it is a cheaper lens. The F is sharper in the corners than the FA too and colours are just a tiny bit punchier.
07-24-2016, 04:19 PM   #12
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Here is my comment (and many will not believe)

It is likely that most of the manual 28mm needs an adjustment to reach infinity.
This is likely the reason why many of them in your results don't seem that good on the edges and even the center at further distances.
Field curvature on many of these 28mm makes it worse on the edges.
In other words, if the center can only be focused to 10m, the edges may at 6m only.


In fact, some of them don't seem sharp at all past the front tree or house in the center (which is suspicious of not being at infinity).

I have noticed it on at least 3 manual lenses that I have on the K1 (never before on other K mount DSLRs).
My K28/3.5 which was excellent on A7 (with adapter that goes past infinity) gave really odd results on my K1 till I sent it for adjustment.


If you have a MILC or knows someone who does, its probably worth a check.


AF lenses seem fine from what I have too (which your F and FA seems to show as well).
07-24-2016, 05:52 PM   #13
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Thanks for your comments. I will check the infinity adjustment. I can so this myself so I will play a little.

Interestingly, I noticed the issue you refer to when focusing the K28/2. That issue aside, this lens performed the best of all the candidates (and appears to be backed up by the largest file size). My order of merit is:

K28/2
A28/2
F28/2.8
FA28/2.8
K28/3.5

(the rest I have not ordered but I say two things. The Tokina ATX 28-85 performed really well and the Tokina ATX 28-70 needs to be redone as it inexplicably shot wide open).
07-25-2016, 04:34 AM   #14
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I like the results from the two f2 lens, too bad you don't have a M28mm f2 here.
07-25-2016, 05:35 AM   #15
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Funny, the Tokina appear to create red cars...
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