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11-13-2022, 11:06 PM   #1
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Question regarding the new forthcoming Pentax DFA 100mm f/2.8 WR macro lens

This new lens has been designed and is apparently in production, and will soon be available. It is shown along with description and specs on the B&H website. I did not think I would be interested, since I've long had the current Pentax DFA 100mm f/2.8 WR macro and have been quite satisfied with it. However, upon taking a better look, I noticed in addition to an upgrade in optics, the new one also features nice, quiet, and most likely improved DC AF. For me this might be a deal-maker. But, I also noticed quite a difference in one particular spec- the minimum focus distance, which for the new one is at 5.1 " where apparently it will deliver its maximum 1x magnification, while the old one is at nearly 12". Would this not mean you would get that maximum 1x magnification with the lens farther from the subject with the old lens, and have to get closer with the new one?

11-14-2022, 12:26 AM   #2
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Perhaps B&H has some typos, as the two lenses have a very similar minimum focusing distance and the new one certainly doesn't have DC autofocus I think the main improvement (beyond the WR -> AW upgrade) is the reduction in aberrations.

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11-14-2022, 12:32 AM   #3
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Where do you get 5.1 inches? The Ricoh web page says the minimum focus distance is 0.303 meters or 11.93 inches for both lenses. The B&H page is probably in error.

https://us.ricoh-imaging.com/product/smc-pentax-d-fa-macro-100mm-f2-8-wr/
https://us.ricoh-imaging.com/product/hd-pentax-d-fa-macro-100mmf2-8-ed-aw/
11-14-2022, 02:13 AM   #4
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Unfortunately, I can no longer bring up the US Ricoh website. My fine, expensive Mac Pro II laptop, bought new about 5 years ago, responds with "This connection is not private" and stating it might be an imposter.

Strange, that B&H would present such misinformation. They are usually reliable. I wonder where their incorrect info came from- maybe mixed it up with that of another brand?

Thanks to both of you for clearing this up. I'm sure others will be or have been misled upon visiting B&H regarding this lens.

11-14-2022, 03:40 AM   #5
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It's basically the same lens with respect to size and auto focus. The only difference is less fringing, if that bothers you with the older lens.
11-14-2022, 07:20 AM   #6
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Ricoh says 13 centimeters which comes to 5.1”.
11-14-2022, 08:14 AM   #7
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It is 13cm from front of the lens, but minimum focus distance is 30.3 cm (from senor).

Although it is probably not the best translation.
QuoteQuote:
This macro lens captures life-size images at a distance of 13 centimeters from the front end to the subject.
The description from Ricoh Imaging JP is better IMO.
QuoteQuote:
A working distance of 13 centimeters (at life-size magnification)...
https://news.ricoh-imaging.co.jp/rim_info2/2022/20221020_037611.html


Last edited by Fogel70; 11-14-2022 at 09:05 AM.
11-14-2022, 10:08 AM   #8
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The confusion is due to the difference in minimum working distance--which is the distance to the front of the lens at 1:1 VS minimum focus distance at 1:1 which is measured to the sensor thus adding the length of the extended lens and the space from the mount to the sensor. Both Ricoh and B&H are correct...
11-14-2022, 01:44 PM   #9
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Ah, right, I forgot about sensor to subject vs front element to subject distances.
11-14-2022, 02:01 PM   #10
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QuoteOriginally posted by Not a Number Quote
Ah, right, I forgot about sensor to subject vs front element to subject distances.
It's when the former is less than the latter that you have a design flaw.
11-14-2022, 02:44 PM   #11
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In practical use it would seem the figure for the front of the lens distance would be more informative. But then B&H gives the other figure for the old lens, which then provides a misleading comparison.

As to the DC AF, this is listed as one of its features in the product description, with a paragraph headed in big letters DC AUTOFOCUS MOTOR which then includes the type of focus system called FREE.

Last edited by mikesbike; 11-14-2022 at 02:55 PM.
11-14-2022, 02:50 PM   #12
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QuoteOriginally posted by Paul the Sunman Quote
It's when the former is less than the latter that you have a design flaw.

......
11-14-2022, 10:16 PM   #13
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QuoteOriginally posted by Ron Boggs Quote
The confusion is due to the difference in minimum working distance--which is the distance to the front of the lens at 1:1 VS minimum focus distance at 1:1 which is measured to the sensor thus adding the length of the extended lens and the space from the mount to the sensor. Both Ricoh and B&H are correct...
B&H are wrong as they specify minimum focus distance as 5.1". They apparently have mixed up minimum working distance with minimum focus distance. They also use the term "minimum focus working distance" in the description which seems to be a mix of both.
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