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Sony 90mm FE macro working distance
- Thread starter erotavlas
- Start date
richj20
Forum Pro
The specs are the minimum focusing distance, which is the distance from the front the lens to the sensor (symbol marked on the camera).
If you want the exact minimum working distance:
- Manually focus to the closest distance.
- Put the camera on a table in front of an object.
- Move the camera until you have the object in sharp focus.
- Then measure the distance from the lens (w/o hood) to the object.
Diablorini
Forum Enthusiast
The working distance is the distance as states being the closes focus distance, this is measure is from the sensor plane - marked at the top of the camera.
So if you want to know the distance from the front of the lens, then you need to factor the length of the lens, with and/or without the lens hood - this should give you the exact distance from the front of the lens (again with or without lens hood) to the subject.
So I would say you had the right idea to begin with.
richj20
Forum Pro
OK, in your case, yes. I thought at first that the lens extends, but I just looked it up, and it doesn't.
(My FE 50mm Macro lens extends.)
So your calculation may be accurate.
- Richard
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bclaff
Forum Pro
I get 280mm (~11 in. closest focus) - 130.5mm (~5 in. lens length) - 18mm (~0.7 in. flange focal distance) = 112.5mm or about 4.4 in.
Since some of the lens length overlaps with the FFD it's probably a fraction of an inch more.
Not sure where your 5.9 inch figure came from.
richj20
Forum Pro
Another opinion:
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www.uglyhedgehog.com
- This third position limits the focus range from about 5-inches to about 10-inches Working Distance,
- MWD of the 90-mm macro lens is 135-mm = 5.3-inches.
- Richard
Of course having the lense.
The effective working distance is a more important factor that the minimum focus distance for a macro lense but is rarely n the pecs.
Even the reviewers often test a macro lense with a chart at 2m from 2.8 to f8, but rarely seen anything at 1.1 from f8 to f22 and also giving the effective working distance ...
The effective working distance is a more important factor that the minimum focus distance for a macro lense but is rarely n the pecs.
Even the reviewers often test a macro lense with a chart at 2m from 2.8 to f8, but rarely seen anything at 1.1 from f8 to f22 and also giving the effective working distance ...
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bclaff
Forum Pro
And if that person has extension tubes they can also measure the focal length at closest focus which I estimate is about 70mm.
I am currently using this lens to make digital copies of 35mm slides using a slide duplicator. I have had to add (front-lens) spacers in order to be able to focus on the slide plane.
I just used a digital caliper to measure the distance from the slide plane to the outmost front edge of the lens that is the length of the total tube and other stuff in the middle. It measures 126mm so that the MWD is certainly less than or equal to 126mm. When I use another combo of spacers that is 3mm shorter (total length of 123mm), the lens can no longer focus on the slide. So the MWD must be somewhere between 124mm and 126mm. I think it's closer to 126mm that is either 125mm or 126mm.
I just used a digital caliper to measure the distance from the slide plane to the outmost front edge of the lens that is the length of the total tube and other stuff in the middle. It measures 126mm so that the MWD is certainly less than or equal to 126mm. When I use another combo of spacers that is 3mm shorter (total length of 123mm), the lens can no longer focus on the slide. So the MWD must be somewhere between 124mm and 126mm. I think it's closer to 126mm that is either 125mm or 126mm.
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bclaff
Forum Pro
Noticed a silly math error in my post.:-O
280mm - 130.5mm - 18mm = 131.5mm (not 112.5mm!)
This is pretty close to the 124-126mm measurement.
That implies th FL at 1:1 is 70 mm.
i measured a little more than that.
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Jim
bclaff
Forum Pro
You could be right, on the other hand ... your thin lens approximation might have done you in.
You might find Measuring Focal Length interesting.
It's a bit more work but I think more accurate (and you can get the internodal distance if you care.)
Regards,
bclaff
Forum Pro
Thanks for the info; you measured working distance from the right place.
The 131.5mm figure is an estimate because the internodal distance (node separation) is unknown.
Also, the 280mm figure is based on the 28cm spec which means it could be 275mm-284mm.
And we don't know how much of the 130.5mm lens length is behind the flange; that could be 5-10mm.
Regards,
You are right, of course.You could be right, on the other hand ... your thin lens approximation might have done you in.
Thanks, Bill.
Jim
bclaff
Forum Pro
If you follow that procedure I'd love to see your results.You are right, of course.You could be right, on the other hand ... your thin lens approximation might have done you in.
Thanks, Bill.
For more complex lenses I suspect that the internodal distance changes with the lens focus setting.
Regards,
I am not sure what difference does it make.
The relevant working distance is exactly what you've measured, the distance from the object to the closest element of the lens (optical element or the barrel). Your lighting setup or a skittish insect wouldn't care whether your optical element is recessed. Nor would they care about the claimed "closest focus" distance measured from the sensor plane, or about the effective focal length (65 mm or 70 mm) at max. magnification.
The real working distance is around 125 mm as you measured, period. Pretty bad for a 90 mm lens, by the way. My 90-mm lens has 175 mm working distance (directly measured) at 1:1 magnification:
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www.dpreview.com
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www.dpreview.com
It may be a while. I'm up to my eyebrows in GFX/lens testing right now. Plus doing some real, uh, photography in between tests. I may have the cart and the horse mixed up.If you follow that procedure I'd love to see your results.You are right, of course.You could be right, on the other hand ... your thin lens approximation might have done you in.
Thanks, Bill.
For more complex lenses I suspect that the internodal distance changes with the lens focus setting.
Jim
bclaff
Forum Pro
Yeah, actual photography can be fun !It may be a while. I'm up to my eyebrows in GFX/lens testing right now. Plus doing some real, uh, photography in between tests. I may have the cart and the horse mixed up.If you follow that procedure I'd love to see your results.You are right, of course.You could be right, on the other hand ... your thin lens approximation might have done you in.
Thanks, Bill.
For more complex lenses I suspect that the internodal distance changes with the lens focus setting.
Here's a (non-Sony and somewhat off topic) shot I got yesterday:
[ATTACH alt="NIKON D7200 70-180mm f/4.5-5.6D ED AF Zoom Micro-Nikkor@178mm d=1'3" 1/250s f/22 ISO 100 w/36mm extension and 2 SB-R200 flashes"]1669626[/ATTACH]
NIKON D7200 70-180mm f/4.5-5.6D ED AF Zoom Micro-Nikkor@178mm d=1'3" 1/250s f/22 ISO 100 w/36mm extension and 2 SB-R200 flashes
Regards,
--
Bill ( Your trusted source for independent sensor data at http://www.photonstophotos.net )
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