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02-17-2014, 11:37 PM - 1 Like   #16
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QuoteOriginally posted by malenisjaj Quote
So, will this hood (58mm) fit on smc 135 f2.5?
According to the Pentax lens database on this site, the Pentax-K 135/2.5 has a 58mm filter thread and should accept the generic hood you have linked to. The genuine Pentax hood you linked to is for the earlier M42 screw-mount S-M-C Takumar 135/2.5 but should fit the Pentax-K 135/2.5 as well, if it indeed the pictured item and not the hood described in the text (55mm thread). The same genuine Pentax hood is much less expensive from KEH at $8.00 USD.

http://www.keh.com/camera/Pentax-Screwmount-Lens-Shades-and-Hoods/1/sku-PS270108000420?r=FE


Steve


Last edited by stevebrot; 02-17-2014 at 11:50 PM.
02-18-2014, 02:25 AM   #17
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Thanks Steve.
02-18-2014, 05:18 AM - 1 Like   #18
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QuoteOriginally posted by malenisjaj Quote
Hi again,
I found some genuine hoods for smc 135 f2.5 on ebay (they are expensive) but something is bothering me since I'm gonna buy cheap chinese copies. On this link there is original hood for 135mm f2.5 and 200mm f4 lenses. It's a hood for 58mm diameter lenses but then again, if you look in description, you'll see this: "Screw-in 55mm screw diameter."

So, will this hood (58mm) fit on smc 135 f2.5?
QuoteOriginally posted by stevebrot Quote
According to the Pentax lens database on this site, the Pentax-K 135/2.5 has a 58mm filter thread and should accept the generic hood you have linked to. The genuine Pentax hood you linked to is for the earlier M42 screw-mount S-M-C Takumar 135/2.5 but should fit the Pentax-K 135/2.5 as well, if it indeed the pictured item and not the hood described in the text (55mm thread). The same genuine Pentax hood is much less expensive from KEH at $8.00 USD.

http://www.keh.com/camera/Pentax-Screwmount-Lens-Shades-and-Hoods/1/sku-PS270108000420?r=FE


Steve
The K135/2.5 and K200/4 both share the same hood. Pentax did this often with hoods

The filter diameter is 58mm so any 58 mm hood will screw in, BUT. If you want to provide the optimum hood, it needs to be at least 50% longer than the stock hood! because the stock hood was based upon the angle of view for a full frame film body, you can make it much longer for a cropped sensor body

If you are purchasing a metal hood, although expensive the long B&K metal hoods are excellent
02-18-2014, 06:00 AM   #19
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And does anyone knows what's the height of genuine pentax hood for smc 135 f2.5? Here there's nothing.

02-18-2014, 01:45 PM   #20
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One question about the hood for smc-a 35-105mm f/3.5. There is a rubber hood (from Pentax) rh-b70 but it's really rare and expensive. I was thinking, if this new models of zoom lens(es) have tulip/petal hoods, why oh why these vintage ones can't? For example, if there were right diameter (and threaded) for this lens (67mm), can the hood for smc-da 18-135mm be adequate for smc-a 35-105mm?
02-18-2014, 02:27 PM   #21
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What is the original hood for a A50 f1.2? Would like to find one or a replica but don't know length or anything.
02-18-2014, 02:50 PM   #22
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QuoteOriginally posted by jaywes Quote
What is the original hood for a A50 f1.2? Would like to find one or a replica but don't know length or anything.
SMC Pentax-A 50mm F1.2 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database
Under description.
02-18-2014, 09:44 PM   #23
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QuoteOriginally posted by jaywes Quote
What is the original hood for a A50 f1.2? Would like to find one or a replica but don't know length or anything.
The height of the hood is not relevant on its own. Assuming pentax made it to the limit, it is the height and diameter that are important. If the replacement is a bigger diameter (at the front of the hood, not the screw thread) it can also be longer because it is the angle of view that is important

Second, if you are using the lens on the DSLR, the hood can be longer still due to the crop sensor.

Get the hoodcalc spreadsheet I uploaded, and make a chart of length vs diameter and then see what is the closest you can get

02-18-2014, 10:54 PM   #24
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QuoteOriginally posted by malenisjaj Quote
if this new models of zoom lens(es) have tulip/petal hoods, why oh why these vintage ones can't?
Any lens that has a non rotating front element could use a Tulip hood, the A35-105 F3.5 rotates when you focus. Manufacturers seem to make more non rotating lenses with tulip hoods now.

Tulip hoods just use a longer top and bottom providing more cover to the lens by taking advantage of the fact that the film or sensor is a wide rectangle and the lens provides a round circle of light on the film plane, so its OK if the hood vignettes badly into the light circle on the top and bottom because that part of the image circle is not seen by the film or sensor.
With a rotating front element the long parts would swing into the rectangular edges of the image as you adjust focus, and you would then see the lens hood vignetting into the image.

The same is true of the square hood I use on my A50 1.4 which does not have a rotating front element. A square hood covers better than a round one if you compare them. But if its on crooked it cuts into the corners of the image.

As far as determining what the max size for a hood is, as was said you just need it to stay outside the max angle of view for the lens, which is much narrower on a given lens with APSC than 35mm film (look in our lens review section where they list both). It could be 10 feet long so long as it doesn't cross inside that angle. Length is only a problem when its not wide enough at a given length to stay outside the angle.
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