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12-08-2010, 08:56 PM   #16
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There's at least one macro lens ( other than those mentioned ) wider than f2.8, and its the one i own, which is a Tamron 90mm f2.5 - earlier version to the f2.8 90mm.

Its a fabulous bit of kit. Its only 1:2 on its own, but sneakily, Tamron released a dedicated Ext Tube for this very lens to bring it true 1:1. It can easily match the quality of the pricier top guns

I also have the original Tamron > PK adapter

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12-08-2010, 09:36 PM   #17
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If you really had to have a macro at f/2.0, you could always modify one and mount a PK mount on it.

You would end up with a fully manual lens... but it would be a f/2.0 macro.

Or... and I just found this one... a sigma 28mm f/1.8 macro that comes in pentax mount.

Only does 1:2.9 but an extension tube can fix that easy enough.

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Here is a sigma 24mm f/1.8 macro that comes in pentax mount. Does 1:2.7

Sigma 24mm F1.8 EX DG ASP for Pentax Macro Lens | Overstock.com

The info on them can be found here:
Sigma Wide-angle Prime lenses for Pentax mount DSLRs | Cameralabs

Thay are made for use with full frame, so you would end up with the equivilent of 42 and 36mm respectively.

And if I am not mistaken.... that would also give you macro of 1:1.93 and 1:1.8 respectively.
12-09-2010, 12:01 AM   #18
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QuoteOriginally posted by cyclone3d Quote
And if I am not mistaken.... that would also give you macro of 1:1.93 and 1:1.8 respectively.
Can you please elaborate on this? Maybe I'm just too slow, but I can't see how. Thanks.
12-09-2010, 02:36 AM   #19
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QuoteOriginally posted by Pentaxor Quote
FA77 + diopter lens. problem solved.
Or for rather less, Helios-44 + dioptre lens. Or for rather more, some 85/1.5 + macro tubes. Et cetera.

QuoteOriginally posted by paperbag846 Quote
Realistically, you might want to tease apart the idea of macro and portrait in your mind.
Quite right. Classically, macro lenses are sharp and portrait lenses are soft. IMHO portraits taken with macro glass are more like ID photos. That's certainly a valid approach to portraits, but can also be done with non-macro lenses stopped down a bit. Or for a cheap mix of both worlds, use a fast projector lens on bellows.

12-09-2010, 06:21 AM   #20
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QuoteQuote:
..Realistically, you might want to tease apart the idea of macro and portrait in your mind....
After some thought, I agree. Low f-stop is not useful for macro because of serious dof problems, but requiring it leaves you with few or no choices.

I like tight framing so I'd get the 55-300mm zoom and a Raynox DCR 150; you'll get both excellent macros up to about 2X and a suberb telephoto to catch your girls at a distance.

Or, add the $50 Raynox DCR 150 close-up lens to your 50-150. It'll yield excellent macros up to 1:1 at a good working distance while retaining all automatic functionality. Then you are free to choose either a wide, portrait, or long lens.

For examples of what to expect with the Raynox see: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/74221-raynox-macro-club.html
12-09-2010, 06:50 AM   #21
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I'd like to remind those who suggest wide lenses (like Sigma 24/1.8) for macro that the wider the lens, the smaller is the working distance (the distance between the lens front element and the subject you're photographing). In my view, lenses wider than 50 mm (24, 35, etc) cannot be used in order to photograph insects in their natural habitat - they will notice you and jump, crawl, fly away. Minimal convenience starts with lenses of focal length 90-100 mm. If, however you plan to photograph static objects, let's say - mushrooms, then wider macro lenses can be used with great success.
12-09-2010, 07:32 AM   #22
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QuoteOriginally posted by newarts Quote
After some thought, I agree. Low f-stop is not useful for macro because of serious dof problems, but requiring it leaves you with few or no choices.
I was wanting a low f-stop for general low light photography, not for macro particularly. I saw the Tamron 60mm macro f/2.0 and figured it could double as both a macro lens, and a general low-light prime. There have been some very helpful suggestions here, but it appears that are precious few such lenses that combine both capabilities as well as the Tamron 60mm...
12-09-2010, 10:46 AM   #23
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I've had wonderful results with extension tubes on 50mm lenses. You can get a 50mm f/1.2 lens which would be excellent for low light, the add an extension tube and stop it down for macro work and have the best of both worlds.

12-09-2010, 12:38 PM   #24
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QuoteOriginally posted by SOldBear Quote
Can you please elaborate on this? Maybe I'm just too slow, but I can't see how. Thanks.
It should work this way - I think - due to the crop factor.

I'll use the 24mm for the example.

You mutliply by 1.5 to get the effective focal length which gives you 36mm.

You should be able to focus just as close as you could with a full frame camera, so it should affect the effective macro the same way, except you divide instead of multiply.

So 2.7/1.5 = 1.8.
12-09-2010, 12:57 PM   #25
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QuoteOriginally posted by cyclone3d Quote
It should work this way - I think - due to the crop factor.
This is another reason why "crop factor" concept is a mistake. It's confusing.

For practical purpose, the only difference between an APS-C sized sensor and a "full-frame" sensor is the size of the sensor. Compared to a "full-frame" sensor, an APS-C sized sensor takes a smaller part of the image projected by the lens.

The focal length of the lens stays what it always is. The minimal focusing distance stays the same. The size of the image, and thus the magnification ratio, stays the same.
12-09-2010, 01:08 PM   #26
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Regarding the Tamron 90/2.5. It is a great lens but from my experience when combined with a 2x TC, the quality doesn't rival a great 1:1 macro like the Sigma 70/2.8. Also it is a bit of a pain to add/remove TC's or extenders in the Adaptall system. EDIT: I first thought the "extender" were a TC. I tried the lens with a TC and didn't like the results. An extension tube is a different matter. It won't degrade IQ as much but it will eat light and decrease the stand-off distance.

Regarding "low light", I think it required ultra fast lenses in film days. Nowadays you are better off cranking up the ISO. The FA50/1.4 doesn't have the best bokeh below f/2.8 and as I said you quickly ran out of DOF at very low f-ratios.

Regarding soft portrait lenses: I'm not a fan of these as I like key features like eyes and eye lashes to be very sharp. AFAIC, to flatter someone with a portrait you always need to do some retouching anyhow so a sharp lens isn't a problem.

Regarding focal length for a macro: I don't think the useful range starts at 90mm. The difference in stand off-distance to a 70mm macro is really small. I think you need to go up to 180mm to get a real difference.

Finally regarding the Sigma 70/2.8's AF speed: It is screw drive and I'm fine even with my lowly K100D. On a K20D or better it will be more than sufficiently fast. It has a long focus range and going through it takes time but that is what the focus limiter is for.

Last edited by Class A; 12-09-2010 at 06:25 PM.
12-09-2010, 01:21 PM   #27
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QuoteOriginally posted by SOldBear Quote
This is another reason why "crop factor" concept is a mistake. It's confusing.
More succinctly, it sucks. It's not a technical term, it's a marketing term, like MACRO ZOOM or 35MM EQUIVALENT or NEW AND IMPROVED or TRADITIONAL VALUES.

QuoteQuote:
The focal length of the lens stays what it always is. The minimal focusing distance stays the same. The size of the image, and thus the magnification ratio, stays the same.
Quite right. The ONLY factors affecting magnification via extension are the FOCAL LENGTH of the lens and the TOTAL EXTENSION on that lens. Subject size and distance, and frame size, do not enter into that calculation. A 50mm lens on 100mm total extension has a magnification of 1x, no matter whether the frame (film or sensor) is 110-m4/3, APS-C, 135/FF, 6x9cm, 8x10 feet, whatever. (This assumes that the subject is in focus.)

And the minimum focusing distance you mention, is the focal length of the lens. No non-reversed lens can focus closer than its focal length, no matter what camera it's on, no matter what size frame its image is projected on. The easy way to test this: put a lens on a bellows. Extend the bellows by various amounts. See how close the lens can focus at each extension.
12-09-2010, 01:24 PM   #28
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QuoteOriginally posted by SOldBear Quote
This is another reason why "crop factor" concept is a mistake. It's confusing.

For practical purpose, the only difference between an APS-C sized sensor and a "full-frame" sensor is the size of the sensor. Compared to a "full-frame" sensor, an APS-C sized sensor takes a smaller part of the image projected by the lens.

The focal length of the lens stays what it always is. The minimal focusing distance stays the same. The size of the image, and thus the magnification ratio, stays the same.
How does that make sense?

Example:

If you have two cameras.. on full frame and one APS-C. Say both have 10MP sensors.

You take the same picture with both cameras with the same exact lens at the same exact distance.

Then you transfer them to a computer and view them both at the same percentage level. The picture taken with the APS-C camera will have a thinner field of view and look like it was taken with a longer lens.

Or am I totally off here? I would love to test a full frame and a APS-C camera side by side to see for myself.

Here is a thread where a k1000 was tested against a *ist D that shows what I am trying to say.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/61827-comparison-3...lots-pics.html

The actual focul length of the lens is the same, but because of the APS-C sensor size, the effective focal length is 1.5 times that of a full frame camera.

Last edited by cyclone3d; 12-09-2010 at 01:36 PM.
12-09-2010, 02:00 PM   #29
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It makes perfect sense. Trouble is, a lot of people want to believe the false magic of ' gaining ' focal length by taking the same lens off a FF camera and mounting on an APS-C, and is perputated by the uninformed who simply repeat what others appear to be saying, and not only them, market sellers too have joined this silly debacle purely on the interests of sales.

Have a cup of coffee, and read thse links.

http://www.digitalcamerareview.com/default.asp?newsID=3611

Field of View Crop Factor (Focal Length Multiplier)

Digital Camera Lens Crop Factor: APS Sesnor Reduces Lens Angle of View On Digital SLR Cameras

DSLR Magnification

www.Clarkvision.com: Crop Factor and Digital Cameras

Crop Sensor (APS-C) Cameras and Lens Confusion

Digital Camera Sensor Sizes: How it Influences Your Photography
12-09-2010, 02:52 PM   #30
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Those links are basically saying the same thing I am.
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