Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-13-2009, 11:58 AM   #61
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by audiobomber Quote
I know how to calculate the resulting macro ratio with a Raynox on a lens when focussed at infinity. Is there a way to tell what kind of magnification adding a diopter will bring at minimum focus? (Obviously not valid for an internal-focus lens).
Magnification is the size of the image on the sensor divided by the actual size of the subject.

With just the original lens objects in focus at infinity have zero size on the sensor, hence zero magnification. As you turn the focusing ring subjects closer than infinity are in focus, hence there is a magnification associated with how close the original lens is to the subject in focus.

Sometimes the original lens' specification gives its maximum magnification ratio, like 1:4 or you can measure it by taking a photo of a ruler.

The minimum magnification of a closeup lens & main lens combo is when the main lens is focused at infinity; call it minimum_close_up_mag.

Minimum_close_up_mag=Original_focal_length/Close_up_focal_length

If the original lens is focused closer than infinity it has an original mag & the equation for total magnification is:

Total_mag=original_mag+minimum_close_up_mag(1+original_mag)

Say you start with a magnification of .25 & use a 2X closeup lens combo, The final magnification is

Total_mag=0.25+2(1+0.25)=2.75

Dave

PS your 16-45 has a maximum magnification of 0.25X at 45mm (according to http://www.dpreview.com/lensreviews/pentax_16-45_4_p15/).

Let's use a Raynox 250 with it; The minimum mag with the Raynox 250 on the 16-45 at 45mm is (I recall you said the Raynox' actual focal length is 109mm):

Min_mag=45/109=0.41X

The maximum mag is:

Max_mag=0.25+0.41(1+0.25) = 0.76X


Last edited by newarts; 07-13-2009 at 12:11 PM.
07-13-2009, 07:59 PM   #62
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,631
QuoteOriginally posted by newarts Quote
PS your 16-45 has a maximum magnification of 0.25X at 45mm (according to Pentax DA 16-45mm 1:4 ED/AL Lens Review: 1. Introduction: Digital Photography Review).

Let's use a Raynox 250 with it; The minimum mag with the Raynox 250 on the 16-45 at 45mm is (I recall you said the Raynox' actual focal length is 109mm):

Min_mag=45/109=0.41X

The maximum mag is:

Max_mag=0.25+0.41(1+0.25) = 0.76X
Interesting. Thanks Dave.
07-16-2009, 08:24 AM   #63
Moderator
Site Supporter
photolady95's Avatar

Join Date: May 2009
Location: Cruising PentaxForums and watching your back.
Photos: Gallery | Albums
Posts: 8,908
Original Poster
I got confirmation that this lens should be here today. I'll shoot some photos this afternoon and post them tomorrow, in Post your photos.
07-16-2009, 09:16 AM   #64
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by photolady Quote
I got confirmation that this lens should be here today. I'll shoot some photos this afternoon and post them tomorrow, in Post your photos.
Yay!

I'm looking forward to seeing not only quality, but how the magnification range on the long zoom works out.

Dave

07-16-2009, 10:37 AM   #65
Junior Member
usapatriot's Avatar

Join Date: May 2008
Location: Miami, FL
Photos: Gallery
Posts: 44
I have a DCR-250 and it works quite well attached to my DA 18-55 II lens, although the the latter mentioned lens does not have the zoom needed to really produce stunning macros. I'm sure if I had a longer lens it would work a lot better with the DCR-250.

07-16-2009, 02:41 PM   #66
Moderator
Site Supporter
photolady95's Avatar

Join Date: May 2009
Location: Cruising PentaxForums and watching your back.
Photos: Gallery | Albums
Posts: 8,908
Original Poster
Well, I tried this afternoon but between the heat and the skeeters, I gave up. It's hard to slap skeeters and try to focus at the same time.

Though I did try before the skeeters hit, but couldn't get this to focus on anything. I guess I need some more instructions on how to use it first. Anyone want to see if they can make me see. I turned off autofocus, and one time I was actually able to see anything, I was about three inches from the subject.
07-16-2009, 03:20 PM   #67
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
The 150 can only focus on objects between around 7 and 8 inches away (depending on where you have the focus ring). That is, focus on infinity to get 8 inches focus distance, set for minimum focus to get about 7 inches. Half those distances for the 250. Might as well set the focus first, before even pointing at your subject, rather than assumign you can set up and then focus. Instead, set the focus, then simply move forward or back until the subject comes into focus. Oh, and DOF is miniscule, so move slowly, or you might move right past the focus point.
07-16-2009, 03:42 PM   #68
Moderator
Site Supporter
photolady95's Avatar

Join Date: May 2009
Location: Cruising PentaxForums and watching your back.
Photos: Gallery | Albums
Posts: 8,908
Original Poster
This is similar to my 135mm macro lens. On 1.5 I have to move up to get anything in focus. Thanks Marc. I'll try again tomorrow morning. I'd try tonight but it is getting stormy looking and I care not to get my equipment wet.

07-16-2009, 03:50 PM   #69
Igilligan
Guest




No worry about getting wet...

The Raynox is a sealed lens
07-16-2009, 05:29 PM   #70
Moderator
Site Supporter
photolady95's Avatar

Join Date: May 2009
Location: Cruising PentaxForums and watching your back.
Photos: Gallery | Albums
Posts: 8,908
Original Poster
QuoteOriginally posted by Igilligan Quote
The Raynox is a sealed lens
Yeah, but I'm not weather sealed.
07-17-2009, 12:46 AM   #71
Veteran Member
res3567's Avatar

Join Date: Sep 2008
Location: Houston Tx.
Photos: Gallery
Posts: 1,876
This shot was taken with my Raynox 250.


Put up yo dukes!

Name:  Macro 078.jpg
Views: 800
Size:  30.6 KB
07-17-2009, 12:50 AM   #72
Veteran Member
res3567's Avatar

Join Date: Sep 2008
Location: Houston Tx.
Photos: Gallery
Posts: 1,876
This shot is with my Raynox 150.



Step into my parlor.....

Name:  Macro 074.jpg
Views: 537
Size:  29.1 KB
07-17-2009, 07:47 AM   #73
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,631
I took a few photos with the DCR-150 in the middle of this thread and finally found time to put them up. The photos below show the DA 16-45 on its own and then with the DCR-150 mounted. Note, these were just done as a test of magnification. I didn't use a tripod and it was a gusty day so the flowers were waving.

DA 16-45mm at f/8


DA 16-45mm with DCR-150 at f/8



The Picasa photos linked here Picasa Web Albums - Dan - Raynox 150 were taken with the 150 mounted on a DA 55-300mm lens. As discussed above, the DCR-150 on a long lens has shallow DOF compared to my D FA 100mm Macro, which makes it more difficult to handle. I like to use flash and f22-32 with the Raynox lenses (the Picasa photos were all taken with natural light).
07-17-2009, 01:40 PM   #74
Moderator
Site Supporter
photolady95's Avatar

Join Date: May 2009
Location: Cruising PentaxForums and watching your back.
Photos: Gallery | Albums
Posts: 8,908
Original Poster
Rob nice capture but I really don't like eight legged creatures...ugh!!

Dan, nice capture on the yellow. I also looked at your album on the DCR-150. I like the bug and the purple flower. Nice crisp and clear on the steman
07-17-2009, 02:05 PM   #75
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,631
QuoteOriginally posted by photolady Quote
Dan, nice capture on the yellow. I also looked at your album on the DCR-150. I like the bug and the purple flower. Nice crisp and clear on the steman
Thanks, but I'm pretty disappointed with that yellow flower on this website. It doesn't pop the way it does in my laptop.

How are you making out with the Raynox, have you given it another try? I was thinking you might be best to try it on your 135mm, or at something less than full zoom on the 70-300, until you get more used to it.
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!
camera, dcr-150, k-mount, macro, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Macro for under 150$? Earth Eater Pentax SLR Lens Discussion 43 10-30-2010 08:29 AM
For Sale - Sold: Raynox DCR-250 Super Macro Lens (Worldwide) ChipB Sold Items 2 10-26-2010 12:21 PM
For Sale - Sold: Raynox DCR-150 Closeup Adapter (US) photolady95 Sold Items 12 06-23-2010 05:37 PM
Macro First test Raynox DCR-150 Caddis Post Your Photos! 2 04-24-2010 08:11 PM



All times are GMT -7. The time now is 03:55 AM. | See also: NikonForums.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