Would a real macro lens improve much on what I have?

**PPPPPP42** · 06-12-2012, 02:42 PM

Originally posted by RioRico

2) Calculating magnification from focal length and distance: M = F/(D-F) where M is magnification, F is lens focal length, and D is subject-lens distance.

So if at 35mm my lens can focus on a piece of paper about 1397mm away (5.5") then my magnification is .026 or 1:4
.026=35mm/(1397mm-35mm)
Wheras a true macro lens is .5 (2:1) and a good one is 1 (1:1)

I guess all I needed was the math to clear things up, thats a first.

That would make my ideal macro lens this one: SMC Pentax-A 100mm F2.8 Macro Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database odd that it costs way more than the new WR FA model.

I do have to work on my technique but please don't rate the pics provided, they were 10 second planning snap shots just to give a vague idea of distance for an example. Plus I never buy training wheels, every single time I don't learn on the higher quality or pro model of something it turns out I outgrow it in a week.

Thanks all.

Last edited by PPPPPP42; 06-12-2012 at 02:53 PM.

normhead · 06-12-2012, 02:57 PM

I thought I knew what macro was with my Sigma 70-300, after I got my Tamron 90 macro , I decided I didn't really know much of anything. AN d if you look at the work of some of the guys on here, I've pretty much decided I'll never know anything. If you're over 50 I suggest auto-focus, the old eyes just don't focus so good anymore.

RioRico · 06-12-2012, 03:00 PM

Originally posted by Philoslothical

A given magnification (e.g. 1:1) gives the same result regardless of focal length. That's what I think he was asking. I also explained the relationship of working distance to focal length.

Yes, we can (theoretically) reach any given magnification, using any given focal length, at the right distance. I say 'theoretically' because reality intrudes upon very short lenses on our (d)SLRs. I *could* put 16mm of extension on my Zenitar 16/2.8 and *theoretically* reach 1:1. Alas, the focus distance would put the subject INSIDE the lens. Talk about bad scratches...

Working distance vs focal length breaks down this way with our (d)SLRs:

* Use a 28mm or 35mm lens either if the studio space is very small, or if we want to shoot fairly close without great magnification. A 28mm close-focus lens that reaches about 1:3.5 is great for objects down to about 13cm / 5in wide. A 35mm lens that reaches 1:1 can work (real close!) a subject about 24mm / 1in wide.

* Use a 40mm or 50mm or 60mm lens when you have or need a little more space. My MacTak 50/4(1x) also works subjects about 24mm / 1in wide, but from slightly further away. Hay, the frame is about 24mm and it's 1:1; sure, a 24mm subject fills the sensor! I consider my 40mm and 50mm macros as indoor, studio lenses.

* Use a 90mm or 100-105mm len s for even more space. Use a 150mm or 200mm for even MORE working distance. Longer than that, it gets clumsy. I don't dare put my P.Navitar 254/4.5 on 500mm extension for 1:1! Lenses of 90mm or longer are usually considered outdoor "in the field" glass. Don't scare the mantids.

Have I wandered too far afield here? Rein me in.

Originally posted by normhead

If you're over 50 I suggest auto-focus, the old eyes just don't focus so good anymore.

Ah, but AF might not focus on the point YOU want it to. Damn robots...

**pacerr** · 06-12-2012, 03:20 PM

Originally posted by RioRico

Ah, but AF might not focus on the point YOU want it to. Damn robots...

And a reminder that at some point it's much easier to attain focus by moving the camera (scrooching a l'il bit?) rather than twisting the lens. And catch-in-focus may be an option too.

GibbyTheMole · 06-12-2012, 05:15 PM

Originally posted by grhazelton

BTW, the Promaster that GibbyTheMole mentions looks exactly like the Vivitar, which also has a Cosina incarnation.

Yep. Forgot to mention that. There's also a Phoenix version. I also forgot to mention the AF version was also sold as the Pentax SMC FA 100mm f/3.5 macro lens. The manual focus version is optically identical, but built a bit better, with smooth manual focusing, which I prefer.

jimr-pdx · 06-12-2012, 06:19 PM

Originally posted by PPPPPP42

At least one that costs less than my truck?

I see a clone of my Sigma 50/2.8 macro for under $250 - but I've never seen your truck

I really like this lens both for its macro abilities and because other than speed it's a really excellent 50mm lens. Focus limiter when you want it, aperture ring too. Oh yes, and full-frame friendly. It may not be your bowl of porridge, but I'm with Goldilocks on this lens - just right.

But if you're happy with your current setup, I'd hate to destabilize your kit. I do that often enough with mine, that's enough for me..

**rbefly** · 06-13-2012, 01:03 AM

Would a real macro lens improve much on what I have?
Yes.

hoanpham · 06-13-2012, 01:45 AM

Originally posted by RioRico

Ah, but AF might not focus on the point YOU want it to. Damn robots...

Shot many and shot more of the same. Perhaps one should be fine?

normhead · 06-13-2012, 05:34 AM

Quote:

Shot many and shot more of the same. Perhaps one should be fine?

That's my approach. And quite often I end up with 80% keepers and can select the best composition rather than going for one shot. I usually set the lens to it's focus point and then back out a tiny bit to be as close to 1:1 as possible.

Tamron 90 2.8 macro (capable of 1:1)

Sigma 70-300 macro ( capable of 1:2. ) While not nearly as good a lens, the Sigma can be picked up second hand for $100.

06-13-2012, 01:03 AM	#22
rbefly Site Supporter Join Date: Oct 2009 Location: Denver, Colorado Photos: Albums Posts: 2,030	Short Version Would a real macro lens improve much on what I have? Yes.

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06-12-2012, 02:42 PM	#16
PPPPPP42 Site Supporter Join Date: Jan 2012 Location: Wisconsin Photos: Albums Posts: 947 Original Poster	Originally posted by RioRico 2) Calculating magnification from focal length and distance: M = F/(D-F) where M is magnification, F is lens focal length, and D is subject-lens distance. So if at 35mm my lens can focus on a piece of paper about 1397mm away (5.5") then my magnification is .026 or 1:4 .026=35mm/(1397mm-35mm) Wheras a true macro lens is .5 (2:1) and a good one is 1 (1:1) I guess all I needed was the math to clear things up, thats a first. That would make my ideal macro lens this one: SMC Pentax-A 100mm F2.8 Macro Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database odd that it costs way more than the new WR FA model. I do have to work on my technique but please don't rate the pics provided, they were 10 second planning snap shots just to give a vague idea of distance for an example. Plus I never buy training wheels, every single time I don't learn on the higher quality or pro model of something it turns out I outgrow it in a week. Thanks all. Last edited by PPPPPP42; 06-12-2012 at 02:53 PM.

06-12-2012, 02:57 PM	#17
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	I thought I knew what macro was with my Sigma 70-300, after I got my Tamron 90 macro , I decided I didn't really know much of anything. AN d if you look at the work of some of the guys on here, I've pretty much decided I'll never know anything. If you're over 50 I suggest auto-focus, the old eyes just don't focus so good anymore.

06-12-2012, 03:00 PM	#18
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Originally posted by Philoslothical A given magnification (e.g. 1:1) gives the same result regardless of focal length. That's what I think he was asking. I also explained the relationship of working distance to focal length. Yes, we can (theoretically) reach any given magnification, using any given focal length, at the right distance. I say 'theoretically' because reality intrudes upon very short lenses on our (d)SLRs. I could put 16mm of extension on my Zenitar 16/2.8 and theoretically reach 1:1. Alas, the focus distance would put the subject INSIDE the lens. Talk about bad scratches... Working distance vs focal length breaks down this way with our (d)SLRs: * Use a 28mm or 35mm lens either if the studio space is very small, or if we want to shoot fairly close without great magnification. A 28mm close-focus lens that reaches about 1:3.5 is great for objects down to about 13cm / 5in wide. A 35mm lens that reaches 1:1 can work (real close!) a subject about 24mm / 1in wide. * Use a 40mm or 50mm or 60mm lens when you have or need a little more space. My MacTak 50/4(1x) also works subjects about 24mm / 1in wide, but from slightly further away. Hay, the frame is about 24mm and it's 1:1; sure, a 24mm subject fills the sensor! I consider my 40mm and 50mm macros as indoor, studio lenses. * Use a 90mm or 100-105mm len s for even more space. Use a 150mm or 200mm for even MORE working distance. Longer than that, it gets clumsy. I don't dare put my P.Navitar 254/4.5 on 500mm extension for 1:1! Lenses of 90mm or longer are usually considered outdoor "in the field" glass. Don't scare the mantids. Have I wandered too far afield here? Rein me in. Originally posted by normhead If you're over 50 I suggest auto-focus, the old eyes just don't focus so good anymore. Ah, but AF might not focus on the point YOU want it to. Damn robots...

06-12-2012, 03:20 PM	#19
pacerr Loyal Site Supporter Join Date: Jan 2008 Location: Paris, TN Photos: Gallery \| Albums Posts: 3,349	Originally posted by RioRico Ah, but AF might not focus on the point YOU want it to. Damn robots... And a reminder that at some point it's much easier to attain focus by moving the camera (scrooching a l'il bit?) rather than twisting the lens. And catch-in-focus may be an option too.

06-12-2012, 05:15 PM	#20
GibbyTheMole Veteran Member Join Date: Nov 2009 Location: Iowa Photos: Albums Posts: 2,275	Originally posted by grhazelton BTW, the Promaster that GibbyTheMole mentions looks exactly like the Vivitar, which also has a Cosina incarnation. Yep. Forgot to mention that. There's also a Phoenix version. I also forgot to mention the AF version was also sold as the Pentax SMC FA 100mm f/3.5 macro lens. The manual focus version is optically identical, but built a bit better, with smooth manual focusing, which I prefer.

06-12-2012, 06:19 PM	#21
jimr-pdx Pentaxian Join Date: May 2010 Location: now 1 hour north of PDX Photos: Gallery \| Albums Posts: 3,897	Originally posted by PPPPPP42 At least one that costs less than my truck? I see a clone of my Sigma 50/2.8 macro for under $250 - but I've never seen your truck I really like this lens both for its macro abilities and because other than speed it's a really excellent 50mm lens. Focus limiter when you want it, aperture ring too. Oh yes, and full-frame friendly. It may not be your bowl of porridge, but I'm with Goldilocks on this lens - just right. But if you're happy with your current setup, I'd hate to destabilize your kit. I do that often enough with mine, that's enough for me..

06-13-2012, 01:45 AM	#23
hoanpham Veteran Member Join Date: Nov 2009 Location: Strand Photos: Gallery \| Albums Posts: 1,366	Originally posted by RioRico Ah, but AF might not focus on the point YOU want it to. Damn robots... Shot many and shot more of the same. Perhaps one should be fine?

06-13-2012, 05:34 AM	#24
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Quote: Shot many and shot more of the same. Perhaps one should be fine? That's my approach. And quite often I end up with 80% keepers and can select the best composition rather than going for one shot. I usually set the lens to it's focus point and then back out a tiny bit to be as close to 1:1 as possible. Tamron 90 2.8 macro (capable of 1:1) Sigma 70-300 macro ( capable of 1:2. ) While not nearly as good a lens, the Sigma can be picked up second hand for $100.