Olympus UK E-System User Group
Olympus UK E-System User Group

Join our unique resource for Olympus Four Thirds E-System DSLR and Pen and OM-D Micro Four Thirds photographers. Show your images via our free e-group photo gallery. Please read the e-group.uk.net forum terms and conditions before posting for the first time. Above all, welcome!


Go Back   Olympus UK E-System User Group > Cameras, lenses and system accessories > Lens focus

Lens focus The place to talk about your camera's glassware.

Reply
 
Thread Tools Display Modes
  #1  
Old 20th June 2011
ScubaRoy's Avatar
ScubaRoy ScubaRoy is offline
Full member
 
Join Date: Feb 2008
Location: Northamptonshire
Posts: 108
Thanks: 2
Thanked 3 Times in 1 Post
Likes: 0
Liked 0 Times in 0 Posts
Macro, aperture & sharpness question

Having read Ian's article on diffraction softening at smaller apertures I have been trying to keep to f8 or wider. The problem obviously comes when trying to get decent DOF for macro subjects where smaller apertures are required.

Say I take a picture using an 50mm lens so the subject fills the frame. If I then attach an EC14 and frame the subject the same then am I correct in thinking that, because I am further from the subject, the DOF will be greater?

Are there any other suggestions on this?
__________________
OMD-EM1, 12-40, E-520, 12-60, 50-200, 7-14, 50, 8, EC14, FL50
Reply With Quote
  #2  
Old 20th June 2011
JohnF JohnF is offline
Full member
 
Join Date: Dec 2010
Location: Oberstedten, Germany
Posts: 56
Thanks: 61
Thanked 8 Times in 4 Posts
Likes: 0
Liked 0 Times in 0 Posts
Re: Macro, aperture & sharpness question

Hi -

The only "real" way to handle the conundrum between needing better DOF and avoiding diffraction softening is to cheat. :-)

Seriously: there is a way to stack photos such that taking a series of photos where the focus varies slightly between pictures to get a nice, overall sharp photo while retaining optimum sharpness. If you simply google "macro photo stacking" you'll find quite a bit of info out there.

If you want to do this a lot, there are hardware solutions out there as well that take it to an extreme, stepping, say, 0.05mm per exposure for several hundred photos. Not inexpensive kit (expect to pay north of 400 quid at the end of the day for hardware and software), but it's pretty much the cat's meow.

Of course, you can do it the proper way as well: move up to a medium format digital back and attach that to a view camera so that you can manipulate the in-focus area to meet your exact needs.

Personally, I find diffraction to first rear its ugly little nebulous head after f11. Sometimes even f16 for longer focal-length legacy equipment (I use an ancient 100mm f4 Leica lens on a bellows, diffraction there is first detectable around f16...and even then is moderate. F22 and beyond, yech.

JohnF
Reply With Quote
  #3  
Old 20th June 2011
Graham_of_Rainham's Avatar
Graham_of_Rainham Graham_of_Rainham is offline
Administrator
 
Join Date: Nov 2007
Location: Rainham
Posts: 8,048
Thanks: 635
Thanked 931 Times in 720 Posts
Likes: 2,239
Liked 1,568 Times in 900 Posts
Re: Macro, aperture & sharpness question

The EC14 will make the 50mm into a 70mm. So @ f/8 with the focus point at say 10 ft
the DoF will go from 2.94ft for a 50mm lens down to 1.47ft for the 70mm lens. In otherwords half

http://www.dofmaster.com/dofjs.html


The E-500 has automatic focus shifting (BKT focus) that works reasonably well, which can then be used to form a stack in PS.
__________________
Graham

We often repeat the mistakes we most enjoy...

Last edited by Graham_of_Rainham; 20th June 2011 at 07:27 PM. Reason: Stacking added
Reply With Quote
  #4  
Old 20th June 2011
Alan Clogwyn
Guest
 
Posts: n/a
Re: Macro, aperture & sharpness question

As I understand it for Macro, to frame a given object, lets say an ant, to fill the frame would give the same DOF no matter what lens or focal length is used, you always need the same F number to get it all in focus.

I may well be wrong but that's how I understand it.
Reply With Quote
  #5  
Old 20th June 2011
ScubaRoy's Avatar
ScubaRoy ScubaRoy is offline
Full member
 
Join Date: Feb 2008
Location: Northamptonshire
Posts: 108
Thanks: 2
Thanked 3 Times in 1 Post
Likes: 0
Liked 0 Times in 0 Posts
Re: Macro, aperture & sharpness question

Thanks for the replies.

I know about the principles of focus stacking but, if I understand it correctly, it requires a number of frames all focussed at slightly different parts of the subject. Unfortuantly, as my main interest is underwater photography, this isn't something that is unlikely to be practical. Just getting the focus in the right place can be challenge enough. Similarly changing the camera isn't something that is an option having just spent a small mortgage on getting the E520 underwater.

Alan - It looks like you are correct. Using the DOF calculator in Grahams link:

50mm focal length @ f8 100cm from subject gives 9.14cm DoF
70mm focal length @ f8 140cm from subject gives 9.13cm DoF

As I rarely print bigger than A4 I guess my only other option is to frame the subject smaller and then crop.

Any other ideas?
__________________
OMD-EM1, 12-40, E-520, 12-60, 50-200, 7-14, 50, 8, EC14, FL50
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
HELP! Sharpness "soft" in exif with sigma 105 macro on e-510. Why? neile Lens focus 2 4th November 2009 06:19 AM
Macro question SkinHead Standard zoom and mid range 12 5th March 2009 01:31 AM
Frozen webs and Aperture question DannyH Foto Fair 10 8th January 2009 07:28 PM
A question about OM Macro lenses bully74uk Lens focus 10 8th December 2008 11:32 PM
Silly aperture Question Garrie Standard zoom and mid range 8 23rd November 2007 05:34 PM


All times are GMT. The time now is 04:34 AM.


The Write Technology Ltd, 2007-2019, All rights reservedAd Management plugin by RedTyger