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07-11-2009, 07:59 AM   #31
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QuoteOriginally posted by audiobomber Quote
I entered the data for 1:1 magnification using a D FA 100mm, then for a Raynox DCR-150 on a 210mm zoom.
??? I don't think you can get 1:1 magnification with a Raynox 150 on a 210mm lens - even focused to infinity, that will probably come in at rather over 1:1. Although the unknown variable here is how much that focal length changes with subject distance - presumably it isn't really 210mm when focused a few inches away. In any case, unless I'm missing something, I don't think you have the necessary information you'd need to calculate the magnification or the DOF when using a Raynox with that zoom.

As for actual question, I don't know the answer. I know that I have heard many times that DOF works out to depend only on magnification, although the *appearance* of the OOF areas will depend on perspective, which depends on distance, which depends indirectly on focal length. But I've also heard the usual DOF formulas for some reason don't properly account for diopters.

07-11-2009, 08:40 AM   #32
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Gus, what did you mean when you said, "the 150 is more usable?"

Ask a question, I forget sometimes, you get more answers than you bargained for.

QuoteQuote:
originally posted by wll.....
I just yesterday ...
after seeing these post, bought a DCR-150 from B&H.

I like all the options of lens use and the small footprint make it something I can always have in my bag .....very cool.
Glad my question helped not just me. I'm getting mine ordered either tonight or Monday.
07-11-2009, 09:39 AM   #33
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QuoteOriginally posted by Marc Sabatella Quote
??? I don't think you can get 1:1 magnification with a Raynox 150 on a 210mm lens - even focused to infinity, that will probably come in at rather over 1:1. Although the unknown variable here is how much that focal length changes with subject distance - presumably it isn't really 210mm when focused a few inches away. In any case, unless I'm missing something, I don't think you have the necessary information you'd need to calculate the magnification or the DOF when using a Raynox with that zoom.
I wish I could find the reference again, but according to the specs that Raynox formerly displayed, the DCR-150 focusses at 211 mm and the DCR-250 at 109 mm. From my reading you will get 1:1 magnification when the FL of the lens matches focus distance. My test illustrates this: https://www.pentaxforums.com/forums/467738-post12.html The 100mm macro lens on its own would be 1:1, adding the DCR-150 gives you 1:2.1 and with the DCR-250 it's 1:0.92.

Forget about how zooms don't match the markings on the barrel when you focus below infinity, it's irrelevant. I'm talking about actual FL, not what the barrel says. Besides, with a Raynox mounted I always focus at infinity.

QuoteOriginally posted by Marc Sabatella Quote
As for actual question, I don't know the answer. I know that I have heard many times that DOF works out to depend only on magnification, although the *appearance* of the OOF areas will depend on perspective, which depends on distance, which depends indirectly on focal length. But I've also heard the usual DOF formulas for some reason don't properly account for diopters.
I've found that DOF is highly dependent on FL and that's what the calculator says too. The other day I photographed a rose bud with a 18-250 set at 250mm and then the 16-45 set at 45mm. I was surprised to see slightly better magnification from the 16-45 as compared to the very long 18-250 (especially since Tamron calls the 18-250 a "macro" LOL). The other thing that struck me was the DOF. The 16-45 had an out-of-focus background, but the 18-250 was pure blur, no detail whatsoever.
07-11-2009, 09:52 AM   #34
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According tothe numbers...

QuoteOriginally posted by Marc Sabatella Quote
??? I don't think you can get 1:1 magnification with a Raynox 150 on a 210mm lens - even focused to infinity, that will probably come in at rather over 1:1. Although the unknown variable here is how much that focal length changes with subject distance - presumably it isn't really 210mm when focused a few inches away. In any case, unless I'm missing something, I don't think you have the necessary information you'd need to calculate the magnification or the DOF when using a Raynox with that zoom.
If the lens is *really* 210mm when focused at infinity, and if the Raynox 150 strength is *really* +4.8 diopter as advertised, the magnification of the combination is 0.210*4.8=1.01 (within 1%.)

I'm guessing this is likely to be the minimum magnification one could achieve with the lens fully zoomed, even for an IF lens (ie. as an IF lens is focused a little closer than infinity, the in-focus image gets a little larger rather than a little smaller.)

Iowan Dave

07-11-2009, 10:07 AM   #35
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QuoteOriginally posted by newarts Quote
I'm guessing this is likely to be the minimum magnification one could achieve with the lens fully zoomed, even for an IF lens (ie. as an IF lens is focused a little closer than infinity, the in-focus image gets a little larger rather than a little smaller.)

Iowan Dave
Nope. I have the 18-250 and DCR-150 mounted right now. I focussed on the Pentax logo on my sling bag. With the lens set to infinity, I can only fit "Pen" in the frame. With the lens set to minimum distance, I can fit "Pentax". This makes sense because when focussed at its minimum, the 18-250 FL is only about 125mm, resulting in 1:1.7 macro. At infinity it should give about 1.2:1.
07-11-2009, 10:23 AM   #36
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I thought I posted something else, but it is no showing up here so evidently, I didn't post it.

I got my money in the bank from the computer sale, went to B&H to buy this 150 and they aren't taking orders until 9pm tonight.....dang it!!
07-11-2009, 10:23 AM   #37
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Here's a brief test I just ran showing the effect of diopter lenses on maximum magnification. I used a Tamron 90mm 2.8 Macro set at 1:2 & photographed my screen's cursor, then added a Sigma +1.6 diopter lens, then a Nikon +2.9 diopter lens. (the working distance decreased with each diopter increase):

As you can see, the increased magnification is is agreement with the predictions:

M=Mo + F*Diopter(1+Mo)

Mo is original magnification

Dave

PS I'll try to demonstrate the depth of field effect, but have tried before and find it hard to do.

Last edited by newarts; 07-12-2009 at 06:58 AM.
07-11-2009, 10:29 AM   #38
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QuoteOriginally posted by photolady Quote
I thought I posted something else, but it is no showing up here so evidently, I didn't post it.

I got my money in the bank from the computer sale, went to B&H to buy this 150 and they aren't taking orders until 9pm tonight.....dang it!!
They must lose a lot of business that way. Have you checked Adorama?

07-11-2009, 10:34 AM   #39
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QuoteOriginally posted by audiobomber Quote
Nope. I have the 18-250 and DCR-150 mounted right now. I focussed on the Pentax logo on my sling bag. With the lens set to infinity, I can only fit "Pen" in the frame. With the lens set to minimum distance, I can fit "Pentax". This makes sense because when focussed at its minimum, the 18-250 FL is only about 125mm, resulting in 1:1.7 macro. At infinity it should give about 1.2:1.
Thanks, Dan

Wow, it seems to work backwards!

Thank goodness I qualified my statement by "I'm guessing"!

Dave

PS does that also imply you can fix the distance from the camera to the subject, then find two different "focal lengths" that give the same size image as by changing the focus?

So the minimum focus of the "250" is really a focal length of 125 - so can you set the focal length at 125 & find a focus that gives the same sized image (at the same distance to the subject?)
07-11-2009, 11:45 AM   #40
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Here's more tests on the effect of diopter lenses on macro Depth of Field; these are photos of my lap-top screen (tilted about 45 degrees with respect to the optic axis all at f2.8):


As you can see, the agreement with theory is reasonable, but I have to admit it is pretty hard to judge just how wide the arrows should be; it is difficult to judge how sharp is sharp enough to be "in focus".

The depth of focus/width of focus ratio is about 1/10 at 1:2 mag it decreases to about 1/16 at 1:1 mag.

Dave

Last edited by newarts; 07-11-2009 at 12:51 PM.
07-11-2009, 12:13 PM   #41
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Dan, yes, I checked with Adorama. Couldn't find it there. Edit: I take that back. I went over there just now, and did a search for Raynox. It shows the 150 with a $2 discount. Since I am ordering some other stuff from them, I'll just get it there.

As for B&H losing business, I doubt that, they're pretty popular and I really don't think they even would worry about losing my business. I only shop there about once a year. Most of the time I order from Adorama mainly because their shipping prices are way lower than B&H's are.
07-11-2009, 12:23 PM   #42
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Order in. I also ordered a step-up ring, and both items would ship free but would not get here until 7 to 10 days, so I opted to pay the extra $5 for 2 to 4 business shipping days. Should be here Wednesday or Thursday.
07-11-2009, 01:22 PM   #43
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QuoteOriginally posted by newarts Quote
does that also imply you can fix the distance from the camera to the subject, then find two different "focal lengths" that give the same size image as by changing the focus?
I tried but couldn't do that. I could get the same magnification at two different FL's using the zoom ring, but I had to change the distance to subject. If I tried to keep the same distance, the magnification changed too radically.

QuoteOriginally posted by newarts Quote
So the minimum focus of the "250" is really a focal length of 125 )
Internal Focus lenses are weird.
07-11-2009, 01:35 PM   #44
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QuoteOriginally posted by photolady Quote
Order in. I also ordered a step-up ring, and both items would ship free but would not get here until 7 to 10 days, so I opted to pay the extra $5 for 2 to 4 business shipping days. Should be here Wednesday or Thursday.
Great, you won't regret it.

I predict you'll be back here looking for tips. Hopelessly thin DOF, tiny apertures and tricky lighting. Macros are a pleasure and a pain.
07-11-2009, 01:49 PM   #45
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QuoteOriginally posted by audiobomber Quote
Great, you won't regret it.

I predict you'll be back here looking for tips. Hopelessly thin DOF, tiny apertures and tricky lighting. Macros are a pleasure and a pain.
Right! Get used to bugs in the freezer*, a semicircle of darkness as the lens shields the subject, a cat's walking across the room jiggling the camera, etc.

Lordy it is fun (I don't do it, I just try to quantitatively & usefully analyze it - who can compete with the macro quality here?)

Dave

*A professional Entomologist recently told me that cold is by far the best way to prepare insects for photography. As they recover from their cold induced suspended animation they will ever so slowly, but naturally, move their legs etc allowing just the perfect photo to slip by you.

I was hoping he had a magic spray, but he opts for cold instead; He did tell me that death does not usually compromise colors, etc, but dead things somehow look un-lifelike (ie. dead.) He thinks maybe one of those freon cold sprays would work in the field?
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