Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-18-2014, 12:09 AM   #16
Site Supporter
ToyTank's Avatar

Join Date: Mar 2013
Photos: Albums
Posts: 675
Original Poster
QuoteOriginally posted by russell2pi Quote

All images will be at most one focal length behind the mirror (which is one quarter of the diameter of curvature).

So in your example, let's say the ball had a diameter of 1 mm. So long as you had 0.25 mm of DOF and you focussed correctly, you could have the entire reflected scene in focus from zero to infinity.
Thank you! What a handy reference. I was looking at the equation and the diagram on "virtual image" page and it makes sense(sort of) to me now. Definitely some interesting possibilities now I need to find more tiny shiny convex things to photograph. I'm thinking a night scene bounced of a convex mirror would be interesting, one way to get sky and foreground without stopping down.

BTW I just swapped out the Tamy 90 on bellows for a reversed Takumar 35/3.5 and it's excellent! I think the 160mm bellows and tiny pixels pushed the tamy past it's limit. The Takumar is much sharper framed the same, with lots of extension left.

01-18-2014, 07:47 AM   #17
Pentaxian
halfspin's Avatar

Join Date: Aug 2012
Photos: Gallery
Posts: 248
QuoteQuote:
that's completely ridiculous nonsense. i seriously don't understand how anyone who's ever looked in a mirror could fail to notice the reflection has depth. are you blind in one eye? if this were true, people would never shoot at f22, they'd just shoot through a mirror to get infinite dof at f1.4.
I apologize that reality does not conform with your preconceived notions.

"Anger is never without a reason, but seldom with a good one"
Benjamin Franklin

"Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong."
Thomas Jefferson
01-18-2014, 09:39 AM   #18
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,556
I totally agree w/ halfspin about the uncalled for post. I would add if I (we) thought trying to be helpful w/o the leisure to sit back and research/wait for everyone else to post would bring such vitriol response I (we) wouldn't do it. And that means the value of this forum would be seriously degraded.
01-18-2014, 09:52 AM   #19
Veteran Member




Join Date: Mar 2012
Location: Perrineville, NJ
Posts: 1,364
The comment about DOF being evident in a mirror is true, but only for a flat mirror. A curved mirror is a lens, which affects the DOF, the same way a fisheye/UWA lens makes almost everything in the room in focus.

The sample photos demonstrate how some portions of the image follow one optical path, while others follow a different optical path. The distortion in the spheres is obvious, but it is perhaps counter-intuitive that the DOF also changes.

01-18-2014, 10:36 AM   #20
Site Supporter
ToyTank's Avatar

Join Date: Mar 2013
Photos: Albums
Posts: 675
Original Poster
Thanks tanzer, what was counter intuitive to me was the degree DOF was affected, but the links russell was kind enough to provide demonstrate the geometry and the handy reference that a shot with DOF 1/4 diameter of the convex mirror should be able to capture everything reflected in the surface, so a smaller mirror requires less DOF and scales down. Yeah so if the ball point pen is 1mm sphere, the FL is .25mm in the reflection the DOF is basically infinite. Something like that
01-19-2014, 12:08 AM   #21
Veteran Member
maltfalc's Avatar

Join Date: May 2010
Location: Winnipeg
Photos: Albums
Posts: 371
this is insane. reflections have depth, period. arrogantly claiming that reality says otherwise and quoting thomas jefferson and benjamin franklin doesn't change that easily demonstrable fact.
01-19-2014, 04:01 AM   #22
Senior Member




Join Date: Sep 2011
Location: Victoria, Australia
Photos: Gallery
Posts: 252
Sure -- but there's probably no need to have kittens over the issue.
01-19-2014, 09:12 AM   #23
Site Supporter
ToyTank's Avatar

Join Date: Mar 2013
Photos: Albums
Posts: 675
Original Poster
What's really insane is I just saved 15% on my car insurance. Oh is that off topic? Sometimes I can't tell and take a thread off the rails

01-19-2014, 09:56 AM - 1 Like   #24
Veteran Member




Join Date: Mar 2012
Location: Perrineville, NJ
Posts: 1,364
Of course reflections do have depth -- and increase in DOF with a wide angle lens is clearly demonstrated in these photos. It doesn't matter whether the lens is refractive or reflective, it is still a lens.
01-20-2014, 04:23 AM - 1 Like   #25
Senior Member




Join Date: Sep 2011
Location: Victoria, Australia
Photos: Gallery
Posts: 252
Nice point Tanzer. The ballpen is something like a 0.25 mm lens.. of course it has incredible DOF!
01-20-2014, 07:22 AM   #26
Pentaxian
TaoMaas's Avatar

Join Date: May 2007
Location: Oklahoma City
Photos: Gallery | Albums
Posts: 3,146
QuoteOriginally posted by ToyTank Quote
In the reflection everything from my eyelashs to the mountains are in focus, but my actual eyelashes are both in and out of focus.

Regarding the reflection of your eye in a mirror: I don't think everything really is in focus. It only seems that way because our eyes refocus on whatever we choose to look at. So when you look directly at your eyelashes to see if they're in focus...they are. Then, when you look directly at the reflected mountains, they seem to be in focus, too, because your eyes have refocused for you. Our peripheral vision isn't good enough to really determine critical focus...we only think it is.
01-20-2014, 08:45 AM   #27
Site Supporter
ToyTank's Avatar

Join Date: Mar 2013
Photos: Albums
Posts: 675
Original Poster
QuoteOriginally posted by TaoMaas Quote
Regarding the reflection of your eye in a mirror: I don't think everything really is in focus. It only seems that way because our eyes refocus on whatever we choose to look at. So when you look directly at your eyelashes to see if they're in focus...they are. Then, when you look directly at the reflected mountains, they seem to be in focus, too, because your eyes have refocused for you. Our peripheral vision isn't good enough to really determine critical focus...we only think it is.
Just to be clear, I'm referring to the photo, where my eye is acting as a convex mirror(AND EVERYTHING IN THE REFLECTION IS IN FOCUS) not when your standing in front of a flat mirror. Thanks for the comment
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!
answer, camera, dof, flickr, focus, help, mirror, pentax help, photography, question, question about dof, reflection
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Rumors about a new Ricoh GXR camera surface online Cynog Ap Brychan Pentax News and Rumors 70 08-01-2013 06:57 AM
Question about buy k5 on the internet foxrock619 Troubleshooting and Beginner Help 6 11-18-2012 10:26 AM
Dumb question about resolution on Optio RS1500 Alliecat Troubleshooting and Beginner Help 6 11-09-2012 07:20 AM
Question about DOF Alberts Troubleshooting and Beginner Help 17 11-03-2011 04:14 AM
Question about DOF aliquis Photographic Technique 12 04-01-2011 07:24 AM



All times are GMT -7. The time now is 10:22 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