Pentaxian Registered: April, 2015 Location: USA Posts: 2,874 | | Review Date: January 14, 2021 | Not Recommended | Price: $75.00
| Rating: 1 |
| Pros: | Well made | | Cons: | Lens element separation makes it unusable | | Camera Used: K10D
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I just purchased a copy of this lens. On the outside it looked new. However, mine has terminal lens separation of the two front elements!
The lens separation looked sort of like haze with some tiny particles in it. But when I took the lens apart and cleaned each element, it because obvious that this "haze" was located between the two cemented front elements. This type of separation is nearly impossible to correct yourself, and I know of no lens repairers who would fix this at an affordable cost. Therefore, my copy of this lens is a functional total loss. I never had the chance to use it as I trashed the lenses after identifying the separation.
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Veteran Member Registered: September, 2017 Location: Medellín Posts: 1,322
3 users found this helpful
| | Review Date: December 23, 2019 | Recommended | Price: $120.00
| Rating: 9 |
| Pros: | Wide open focusing with the Auto Bellows and/or extension tubes. | | Cons: | Most copies have separation. | | Sharpness: 10
Aberrations: 8
Bokeh: 9
Handling: 10
Value: 10
Camera Used: Film cameras, K-5
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It's a nice lens for tabletop photography. Funny thing is, it focuses to infinity on the Auto Bellows. Works just as intended on it. Got everything as a kit from a forum member. I first used it with the original Asahi Pentax double cable release and a Canon T3 threaded cable release adapter and later with a modified Nikon AR-10.
Sadly, all copies I've ever seen suffer from a bit of separation on the edges, but that really doesn't seem to affect it since one rarely shoots wider than f/8 or wide open at infinity. That's not what this lens is for anyway, although there's still the option. I would rather take the 50 mm or 100 mm plus other auto tubes combined to use in the field. Less weight and still wide open focusing. Clip on hood works well. Fits all in the small case.
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New Member Registered: November, 2013 Posts: 14
1 user found this helpful
| | Review Date: November 11, 2018 | Recommended | Price: $100.00
| Rating: 10 |
| Pros: | an excellent cose ups lens | | Cons: | some very few CA's | | Sharpness: 10
Aberrations: 9
Bokeh: 10
Handling: 9
Value: 10
Camera Used: k--5,k-s1, k-x, k200d fuji x-t100+x-e1
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Important tip: Without an additional bellows extension you'll get never sharp images, shan't you ? 
a very good performer:
++ very good sharpness (80 LP/mm)
++ high contrast
++ no distorsion (=%)
+/++ very small CAs (sometimes especially in bokeh visble)
for macro shootings you can improve sharpness by using a self made focal reductor of an achromatic top lens element of a binocular 8x30, integrated into an extensions tube 12mm, so you'll get a 2.8/70 or 3.5/85 mm macro lens with extreme sharpness on bellows
for photos taken in this way excellent results !!! approx. 90 LP/mm - a professional value !
Highly recommended !
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Site Supporter Registered: October, 2008 Location: Vancouver, Canada Posts: 8,089
3 users found this helpful
| | Review Date: January 18, 2009 | Recommended | Price: $120.00
| Rating: 8 |
| Pros: | Size, quality and 100mm focal length. | | Cons: | Slow f4.0, limited usage as it’s dependant on a bellows unit. | | Camera Used: K Series film bodies (K1000, KM, KX, K2, K2DMD)
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The K100/4 Bellows definitely falls into the specialty lens category. It’s basically unusable without a bellows unit, as the lens has no focusing ring to control magnification. The K100/4 Bellows has an automatic diaphragm which will be retained when used with the “auto” bellows unit, or it can also be used on the “regular” bellows unit as a manual diaphragm lens. For me this limits the K100/4 Bellows to indoor macro use only. For outdoor use I’ll take my rail kit, extension tubes and regular macro lenses, which are far more durable than a bellows unit.
However, if you don’t have a Bellow Unit or don’t want to use one outdoors, you could use the K100/4 Bellows lens with Extension Tubes and these two options for focusing:
1) Use a macro focus rail to focus the K100/4 Bellows and use Pentax Auto Extension tubes for magnification. This option will preserve the lenses automatic diaphragm and would require a tripod for the focus rail.
2) Use the Pentax Helicoid (variable) Extension Tube to focus the K100/4 Bellows on its own or add more Pentax Extension (Auto or manual) tubes for higher magnification. As the Helicoid tube does not maintain the full aperture metering mechanism of the K100/4 Bellows lens, you will have to use stop-down metering. This is a good handheld option, as the K100/4 Bellows does not weigh very much and neither do these extension tubes. I tried this option and it worked pretty well, though the Helicoid tube on its own does not give you very much magnification. (About the same as using a Pentax Close-up filter attachment on a regular 100mm lens.)
The K100/4 Bellows is rather slow at f4.0, so you get a darker viewfinder especially if used indoors. I compensate the slow maximum aperture by using two 500-watt portable studio lights when I’m doing indoor macro shooting.
The 100mm focal length gives you a longer distance to subject ratio than the 50mm macro; this is nice when using the bellows unit on a tripod. For extreme magnification in macro photography, the 100mm focal length does not benefit when the lens is reversed. You are better off reversing the 50mm macro or the K28mm f3.5, for magnification greater than 1.0. The K 28mm f3.5 is still the best Pentax lens for this purpose.
Even though the lens element is recessed, you should use the dedicated plastic round clip-on lens hood. This hood is shared with the K85/1.8, K100/4 Macro & the K105/2.8 lenses. (52mm filter diameter)
All in all it’s a valuable tool if you are into macro photography and have other macro lenses to compensate for some of its weaknesses.
Sample shots taken with the K100/4.0 Bellows. Photos are medium resolution scans from original negatives.
Camera: K2 Film: Kodak Portra 400VC ISO: 400
With PENTAX Bellows Unit K
Camera: K2 Film: Kodak Portra 400VC ISO: 400
With PENTAX Bellows Unit K
Camera: KX Film: Kodak Pro Image 100 ISO: 100
With PENTAX Helicoid Extension Tube K
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