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Depth of field scale
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PostPosted: Mon Dec 04, 2017 8:52 am    Post subject: Depth of field scale Reply with quote

Hi again
This is likely a silly question but I cannot find the answer on Google.
The older lenses have a Depth of field scale to roughly tell us how much of the picture will be in focus, I understand how that works, what I do not know is what the capital R stands for?
On the lenses I have it is situated on the RHS of the scale between the f4mark & f11. (As you look down on the lens holding the camera as if you were about to take a photo.

Any one able to help?


PostPosted: Mon Dec 04, 2017 9:45 am    Post subject: Reply with quote

IR index ?


PostPosted: Mon Dec 04, 2017 10:00 am    Post subject: Reply with quote

Indeed, that's the infrared index.
You may read this for better understanding: https://www.lifepixel.com/infrared-photography-primer/ch2-basic-theory-infrared-focus-marks-on-lenses


PostPosted: Mon Dec 04, 2017 10:47 am    Post subject: Reply with quote

tb_a wrote:
Indeed, that's the infrared index.
You may read this for better understanding: https://www.lifepixel.com/infrared-photography-primer/ch2-basic-theory-infrared-focus-marks-on-lenses

I've never seen a zoom with 2 IR marks as they mention. but I have several push pull types with a line giving IR focus throughout the zoom range.
FWIW the marks are not always on the same side it depends on the lenses design. Fortunately they are little needed these days as cameras have live-view allowing focusing with what the sensors seeing, whether or not this is visible to the photographer.


PostPosted: Tue Dec 05, 2017 7:58 am    Post subject: Reply with quote

Here are a few different IR markings from around the net.
http://www.kenrockwell.com/nikon/images1/55mm-f35/D3S_6854-1200.jpg
http://www.apogeephoto.com/wp-content/uploads/2016/mag1-4/mfir_MichaelFulks_photos/field.jpg
http://www.minolta.suaudeau.eu/articles/optiques/telezoom/Minolta_Comparaison_telezoom.jpg
https://static1.pointsinfocus.com/2010/07/modern-distance-scales-useless-fluff-or-useful-tool/Manual-focus-lens-distance-scale.jpg
http://cdn.northlight-images.co.uk/wp-content/uploads/2015/10/dof_lines.jpg
http://c8.alamy.com/comp/FBCJJP/film-slr-camera-with-zoom-lens-showing-depth-of-field-scale-FBCJJP.jpg
http://forum.mflenses.com/userpix/20102/14_Vivitar_S1_70210_lenses_2.jpg
https://www.pentaxforums.com/gallery/images/273/1_v70210-chart-pic.jpg

I've never seen a zoom with 2 IR marks for the zoom extremes, most often it's a curved red line.


PostPosted: Tue Dec 05, 2017 8:08 am    Post subject: Reply with quote

Thanks everyone for all of the responses. As I am using these lenses on a modern Sony camera I can assume that I do not need to worry about it? The Sony will not do infra red unless modified as far as I know.
Was good to find out though, my curiosity is satisfied!

Thanks


PostPosted: Wed Dec 06, 2017 9:19 am    Post subject: Reply with quote

adonuff wrote:
Thanks everyone for all of the responses. As I am using these lenses on a modern Sony camera I can assume that I do not need to worry about it? The Sony will not do infra red unless modified as far as I know.
Was good to find out though, my curiosity is satisfied!

Thanks


If you put a IR filter in front of your lens, your camera will probably still see something. Very long exposures may be needed if the cameras not modified, but with a tripod, higher ISO & moderatly wide apertures you probably can experiment a bit with IR, just for the cost of the filter. (Chinese 720nm filters are <£20)
Of course even for that the IR mark isn't too relevant.