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07-12-2012, 08:23 AM   #16
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there is a spreadsheet called Hoodcalc which I uploaded some time ago. this can be used to calculate the maximum round filter that can be used for the lens based upon sensor format

07-12-2012, 11:44 AM   #17
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QuoteOriginally posted by Lowell Goudge Quote
there is a spreadsheet called Hoodcalc which I uploaded some time ago. this can be used to calculate the maximum round filter that can be used for the lens based upon sensor format
I wonder if there is a way to get it to work for the SoldBear stepdown ring style of hoods?
07-12-2012, 12:12 PM   #18
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The calculation uses the actual diameter of the front element , the diameter of the opening, the distance from the opening to the front element (including any set back in the lens from filter threads to front element), and the FOV as a function of sensor format.

as long as the hole is larger than the FOV for the front element diameter, and hole to front element distance, probably. Note here i keep saying front element diameter and not filter thread. I am deliberately being very specific here. My SMC-M 100/4 has a front element diameter of 25mm. so something quite a bit smaller than the 49mm filter thread still will not necessairly impact the FOV
12-18-2012, 10:25 PM   #19
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49mm-28mm step down ring?

QuoteOriginally posted by seventysixersfan Quote
I just have to say that I am so very happy with my new F 28mm attached to my K-X; it feels like a perfect match-- great FOV, compact and light, excellent IQ. It may well get stuck to my camera for a while...
I am waiting for my Pentax-A 28mm f/2.8 to arrive (without a hood) and I am wondering which hood to use.

Did you use a 49mm-28mm step down ring instead of a hood?

I'm finding it difficult to understand how that can work in full aperture, excuse my 'noviceness'

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12-18-2012, 11:13 PM   #20
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QuoteOriginally posted by nocturnal Quote
Did you use a 49mm-28mm step down ring instead of a hood?

I'm finding it difficult to understand how that can work in full aperture, excuse my 'noviceness'
I'm using 49-28mm stepdown ring for Pentax DFA 100WR Macro, DFA 50 Macro, FA 50 F/1.7.

My F 28mm F/2.8, before sold to Blue, also had a 49-28mm (I think he's still using it that way). So did my Tamron 90mm Macro and Sigma 50mm Macro (both sold).

This is not my idea. I was just inspired by the hood of the Pentax DA 40mm Ltd.

12-19-2012, 06:18 PM   #21
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QuoteOriginally posted by SOldBear Quote
I'm using 49-28mm stepdown ring for Pentax DFA 100WR Macro, DFA 50 Macro, FA 50 F/1.7.

My F 28mm F/2.8, before sold to Blue, also had a 49-28mm (I think he's still using it that way). So did my Tamron 90mm Macro and Sigma 50mm Macro (both sold).

This is not my idea. I was just inspired by the hood of the Pentax DA 40mm Ltd.
I still have that F 28/2.8 and that is the hood set up I use on it. It works well and looks good.
12-19-2012, 07:33 PM   #22
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QuoteOriginally posted by Blue Quote
I still have that F 28/2.8...
My son is still nagging me for selling the lens. He prefers it to the Sigma 30mm F/1.4, and says that the DA 21mm is just too wide at times.
12-19-2012, 07:55 PM   #23
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QuoteOriginally posted by SOldBear Quote
My son is still nagging me for selling the lens. He prefers it to the Sigma 30mm F/1.4, and says that the DA 21mm is just too wide at times.
It is an under appreciated lens. It was one of the lenses I took to Haiti with me in October.

12-20-2012, 09:30 AM   #24
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QuoteOriginally posted by nocturnal Quote
Did you use a 49mm-28mm step down ring instead of a hood?
I went with the cheap Adorama rubber hood that works well but it is a bit bulky. I'm very tempted to try the 49mm-28mm step down ring approach. I saw one offered on ebay for $2; not sure if this would work but for the price it might be worth a shot!

49mm to 28mm Step Down Filter Ring Adapter 49 28 | eBay
12-20-2012, 09:39 AM   #25
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QuoteOriginally posted by seventysixersfan Quote
I went with the cheap Adorama rubber hood that works well but it is a bit bulky. I'm very tempted to try the 49mm-28mm step down ring approach. I saw one offered on ebay for $2; not sure if this would work but for the price it might be worth a shot!
I have a standard 49mm rubber hood on my FA 28mm now and a 49-28 step-down on order. I tried the DA 40mm hood and it vignetted noticeably.
12-20-2012, 09:45 AM   #26
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from where did you order your 49-28 step down may I ask?
12-20-2012, 10:39 AM   #27
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QuoteOriginally posted by seventysixersfan Quote
from where did you order your 49-28 step down may I ask?
EBay Canada, from the same company as shown in your link above.
12-20-2012, 11:00 AM   #28
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great, thanks Dan!
12-20-2012, 11:17 AM   #29
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QuoteOriginally posted by seventysixersfan Quote
great, thanks Dan!
I dont' know how it will work yet, but if it vignettes I intend to file away the corners.
12-20-2012, 02:19 PM   #30
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QuoteOriginally posted by audiobomber Quote
I dont' know how it will work yet, but if it vignettes I intend to file away the corners.
Did it vignette?
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