Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-10-2008, 02:17 PM   #1
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
50mm FA 1.4, 18-55 AL II Kit Lens and 16-50mm DA* Pics

I bought a 16-50 DA* today and took a snap of a magazine page using the FA 50mm f/1.4 prime, 18-55mm 3.5-5.6 AL II kit lens and the new 16-50mm DA*. I was in Av @ 5.6, ISO 100. I did add +1EV for the 18-55mm kit lens because it's always -1ev or more on my camera for some reason. Other than that, I made no other corrections. The word in the center, "also" was my focus point. This is a 100% crop on the center of the image.

18-55mm AL II


16-50mm DA*


50mm prime


Now, I do not know what this test really proves, but I did find a few things interesting.

#1... The 16-50mm set to 50mm produces a wider image than my 50mm prime.
#2... The prime was brighter, washing out the image a bit
#3... The 16-50mm is a big step from the kit lens (obviously)

Now, I have 10 days for a complete refund and 30 days to exchange. How can I test my lens to make sure it's a good batch? My serial number is 9029841. I paid a higher price from a local retailer so that I could easily return, get another if necessary and I want to take advantage of that, if necessary. I don't want to go searching high and low to find a fault, but if my lens has a common problem and could/should be better, I would like it to be and think I paid for a good one :-)

Thanks for any input,

Jeremy

12-10-2008, 09:19 PM   #2
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by jeremy_c Quote
#1... The 16-50mm set to 50mm produces a wider image than my 50mm prime.
It's very typical with zooms that they only achieve their stated focal length when focuses at infinity. The closer in you focus, the wider the angle of view becomes even when leaving it at the same focal length setting.

BTW, if your kit lens produced an image that dark with +1EV, something would seem seriously wrong...
12-10-2008, 11:46 PM   #3
Veteran Member
arbutusq's Avatar

Join Date: Sep 2006
Location: Vancouver BC canada
Photos: Gallery
Posts: 380
A better wayto do the test is to set the camera up in manual mode, using the same Av and Tv. The 18-55 will be a bit darker than other lenses even with manual for some reason. I did a test about that a year ago and posted the results on the forum. The test I posted was with the 16-45 but I have tested it with other lenses as well.
12-11-2008, 01:59 AM   #4
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,348
QuoteOriginally posted by arbutusq Quote
A better wayto do the test is to set the camera up in manual mode, using the same Av and Tv. The 18-55 will be a bit darker than other lenses even with manual for some reason. I did a test about that a year ago and posted the results on the forum. The test I posted was with the 16-45 but I have tested it with other lenses as well.
He has got the same aperture and ISO and almost the same exposure time, so I'd say it is good enough comparison.

And it does look like the DA*16-50 is sharper than the A50/1.4! I must get one.
Could you post similar shots at f2.8? These are at f5.6.

Thanks for posting!

12-11-2008, 07:41 AM   #5
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by arbutusq Quote
A better wayto do the test is to set the camera up in manual mode, using the same Av and Tv. The 18-55 will be a bit darker than other lenses even with manual for some reason. I did a test about that a year ago and posted the results on the forum. The test I posted was with the 16-45 but I have tested it with other lenses as well.
One of my complaints with the 18-55 was I always had to do +1EV at least when in any program mode (Sv, Av, Tv, TAv, P, or Green). I was wanting to test how the camera handled each lens in a manner I would normally shoot. For instance, I have taken quite a few shots w/my prime, then put on my 18-55 and forgot to add the +1EV and shot away. I am sure I'll be doing plenty more of that.

Now, with the 16-50, seems I don't have to remember to do a +1EV at all on it because the camera handles the lighting just fine. As for the 18-55, I'll probably put it back in it's original box and store it incase my other lens needs to go back for repair or something. I'm pretty sure I will not get anything reasonable out of a kit lens on the used market.

Jeremy
12-11-2008, 07:43 AM   #6
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by Marc Sabatella Quote
BTW, if your kit lens produced an image that dark with +1EV, something would seem seriously wrong...
I agree. I did post on the forum asking a question about it before but the general consensis was that the kit lens did produce darker lenses. It was suggested that I get a new focus screen. Here is the original thread about my +1EV requirement:

https://www.pentaxforums.com/forums/general-pentax-photography/42619-50mm-pri...pose-same.html

Jeremy
12-11-2008, 11:07 AM   #7
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by Douglas_of_Sweden Quote
And it does look like the DA*16-50 is sharper than the A50/1.4! I must get one. Could you post similar shots at f2.8? These are at f5.6.
I want to play a bit with my 50mm prime. I did a few focus tests (Home) and it seems that my 50mm prime is front focusing quite heavily. I need to redo the tests to make sure. After I get that sorted out, I'll do a similar test at 2.8.

Jeremy
12-11-2008, 11:24 AM   #8
Veteran Member
ghelary's Avatar

Join Date: Jul 2008
Location: Paris, France
Photos: Gallery
Posts: 617
2 different lenses of the same focal lenth and at the same aperture won't expose the same.

The reason that the light transmitted on the sensor is not only function of the diameter of the front element of the lense (which determine aperture) but also function of the absortion of the glass elements of the lense.

So if you compare a zoom and a prime, at same focal lense and same aperture, with all other elements equal in manual mode, the image for a zoom will be significantly darker due to a higher number of elements (as compared to the prime)

For that reason, movie technicians speaks about T-stops (for transmission) and not f-stops.

regards,
Guillaume

12-11-2008, 11:42 AM   #9
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,676
QuoteOriginally posted by Douglas_of_Sweden Quote
And it does look like the DA*16-50 is sharper than the A50/1.4! I must get one.
In the quick in-store testing I did, the 50mm F1.4 was sharper at 2.8 than the 16-50 was at F4.

My 18-55mm underexposes by .7EV.
12-13-2008, 06:02 AM   #10
Veteran Member
kristoffon's Avatar

Join Date: Aug 2008
Location: Brazil
Posts: 532
Without fixing the exposures this comparison is useless... If you can't get well exposed photos from the camera then please do shoot RAW, ISO 280, and fix it there.
12-13-2008, 09:09 AM   #11
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by kristoffon Quote
Without fixing the exposures this comparison is useless... If you can't get well exposed photos from the camera then please do shoot RAW, ISO 280, and fix it there.
A great deal of my test was to see how the camera was able to expose them. I don't want to have to go into manual mode all the time or tweak my settings. So, if the 18-55 does not expose correctly all by itself, that's a major problem to me. Likewise, if the 50mm prime I have over exposes all the time, that seems to be a problem to me as well.

I wanted to test the whole package, not simply the lens.

Jeremy
12-13-2008, 06:34 PM   #12
Veteran Member
kristoffon's Avatar

Join Date: Aug 2008
Location: Brazil
Posts: 532
QuoteOriginally posted by jeremy_c Quote
A great deal of my test was to see how the camera was able to expose them. I don't want to have to go into manual mode all the time or tweak my settings. So, if the 18-55 does not expose correctly all by itself, that's a major problem to me. Likewise, if the 50mm prime I have over exposes all the time, that seems to be a problem to me as well.

I wanted to test the whole package, not simply the lens.

Jeremy
I´m sorry but there must be something wrong with your lenses or camera. I have the FA 50 and the 18-55 kit lens, plus very many others, and would certainly have noticed if there were such a huge problem exposing my pictures. My 50mm prime doesn´t overexpose and my kit lens doesn´t underexpose.
12-13-2008, 09:58 PM   #13
Senior Member
kibipod's Avatar

Join Date: Oct 2008
Location: Ohio
Posts: 276
fa 50mm soft?

may be you need to do the focus calibration again to get rid off ff. 16-50mm did nice job.
12-14-2008, 01:34 PM   #14
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by kibipod Quote
may be you need to do the focus calibration again to get rid off ff. 16-50mm did nice job.
I have not done a focus calibration on it. I do have a chart from pentaxdslrs.com and I'll give that a go.

Jeremy
12-14-2008, 06:20 PM   #15
Inactive Account




Join Date: Nov 2008
Location: Ohio USA
Photos: Gallery
Posts: 96
Original Poster
QuoteOriginally posted by kibipod Quote
may be you need to do the focus calibration again to get rid off ff. 16-50mm did nice job.
Ok, I did fix the focus issue. The prime needed a +5 :-/ Attached are center crops of the new test. The wider view is the 16-50mm (set at 50mm). I used manual mode in this case. ISO 100, f/8, 3sec exposure. You can view full sized images at:

http://jeremy.cowgar.com/files/1650DA-STAR-full-cereal.jpg
http://jeremy.cowgar.com/files/FA50-f1_4-full-cereal.jpg

Jeremy
Attached Images
View Picture EXIF
PENTAX K20D  Photo 
View Picture EXIF
PENTAX K20D  Photo 
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
16-50mm, 18-55mm, 50mm, 50mm fa, da*, days, ii, image, k-mount, kit, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: K20d kit + flash + extra; FA 50mm 1.4; DA 50-200mm, M 50mm Macro (Worldwide) cambridge Sold Items 16 06-04-2010 09:22 AM
k-x lens , kit 18-55mm f3.5-5.6 AL , what 50mm f1.4 can do over kit lens? crossing Troubleshooting and Beginner Help 19 01-15-2010 03:23 PM
For Sale - Sold: Pentax K-X (black) with kit lens and F 50mm f/1.7 lens tangus Sold Items 3 01-06-2010 09:42 AM
Pentax 50mm M 1.7 lens pics fevbusch Pentax SLR Lens Discussion 23 03-20-2007 06:35 PM



All times are GMT -7. The time now is 08:13 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top