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08-12-2009, 06:16 PM   #31
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QuoteOriginally posted by newarts Quote
Look for a Pentax Macro-Takumar 50mm f4 1:1 it is a screw type lens and therefore needs a $15 mount adapter.

This is a superb lens, the only early 1:1 macro by Pentax.

Note there are two aperture rings on the end of the lens.
There's one on eBay now at $85: Asahi Macro Takumar 50mm f/4 Lens M42 for Pentax NR - eBay (item 190326260915 end time Aug-13-09 16:41:12 PDT)

If the ad says anything about SMC or multicoating it is not the right lens. Maybe you can find one for less, but not much less.

Dave in Iowa usually
I second this! It's a preset M42 lensthat goes to 1:1. I have it. I like it. You can also use it as a regular stop down 50mm lens. It is a great lens.

The ONLY difference between this lens and the SMC version is that the SMC version only goes to 1:2 because of the open ap linkage. I have both.

The only point I disagree with dave on is the price. Sometimes you can catch a bargin on these for $50.

If you want to go to 100mm, The best is the 100mm SMCTM. It is a heliar design. It produces the nicest looking images. I have about six 90-105mm macro lenses (old Viv series 1, new vivitar, Canon, SMCTM, Kiron,...).

Ext tubes are cheap, but harder to use and have light loss. A supplementary (close up) lens is easier but must be removed for any other lens use. You can only focus at one magnification and one distance, about 250mm in front of the front element. Even the best ones introduce some distortion. I've seen it. I've used expensive Canon triplet and doublet 240mm suppplementals. Plus any suplemental adds its distortion to the primary lens. If it is a zoom, you are already off to a bad start. Supplementals are not flat field either. With a supplemental, it is harder to get the entire field in focus if it is someting flat like a coin, stamp or a watch face. They are great for a trip where you can slip a small supplemental in your bag rather than drag around another full size lens.

The stopdown (two ring) ST 50mm macro lens has continuosly adjustable magnification down to 1:1 and can focus from the front element to infinity. It is a flat field lens wihich is very good if you take pictures of stamps or coins or what ever other flat things that you can't think of now. You put this lens on your camera in the morning, you can walk around and take macro shots, portraits, or landscapes without changing this super sharp lens all day.

A 50mm 1:1 macro is the same price or slight more expensive than a raynox and better and more versatile. It is much cheaper than the Canon supplemental triplet and once again more versatile and better. It is a no brainer the Pentax 50mm 1:1 preset macro is better and cheaper.

08-12-2009, 08:36 PM   #32
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Great observation about f-stop, raynox, DOF, etc Dan.

Here's what's going on I think. The effect of adding a diopter close-up lens to a another lens is to create a new lens with a different focal length. The formula is:

1/f_new_meter = 1/f_old_meter + diopter

So for a 210mm lens with a 4.8 diopter lens added, the focal length of the combination is 105mm.

The iris diaphram opening hasn't changed, but the focal length has; therefore the f-stop has changed. The new f-stop is:

F-stop_new=Focal_length_new/aperture=F-stop_old*Focal_length_new/Focal_length_old
or,
F-stop_new = 11*105/210 = 5.5

So the effective f-stop has dropped from 11 to 5.5!

for the same magnification, this drops the depth of field by the same ratio, 5.5/11 = 1/2; a factor of two!

I think this is in good agreement with your observation; with the Rayox the DOF is lower at the same magnification and nominal f-stop because the actual f-stop is much lower (because the focal length is decreased.) I snagged your posted images and compared their DOF's.



I used the letters to estimate DOF rather than the coin because it was easier; it looks to me like the DOF of the Raynox image is about 1/2 that of the 100mm lens in keeping with the prediction (but this is hard to pinpoint).

Therefore in the DOF equation,

DOF/WOF=C*N*WOF(1+1/m), N is the actual F-stop as modified by any auxiliary lens.

Thanks for posting your photos & observations. I think I understand what's going on a little better. I think if you increase the Zoom (210) + Raynox F-number to 22 the photos will look the same.

Dave

PS I guess a teleconverter will have the opposite effect on actual f-stop - adding a teleconverter will increase the dof (at the same mag & nominal f-stop on the primary lens.)

Last edited by newarts; 08-12-2009 at 08:49 PM.
08-12-2009, 10:56 PM   #33
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QuoteOriginally posted by audiobomber Quote
Are you maybe talking about the Raynox 250? It has a focal length of 109mm, which would give almost 1:1 macro at 100mm. For the photos above I used a FL of 210mm, which is the stated focal length of the DCR-150 and therefore gave me 1:1 macro. If I had set the 55-300 for 100mm, I would get more DOF, but I would not get 1:1 macro. If I try to move in too close, I lose focus.

The DCR-150 is quite useable on the 55-300mm at 300mm, but you need an extremely small aperture for a useable DOF. The result is about 1.4:1, pretty serious magnification. At 300mm I normally use an aperture of F32 and a flash.

I'll respond to the rest of your post after I try another test.
no, it's not a 250. what I meant is that you should get a 1:1 magnification with a better DOF at 150. I guess you already did the test and saw what I meant. I mentioned the 100mm FL because that is where I got the best magnification coming from the 55-300 (though not 1:1) at infinity focus. the 150mm that I said is where you could achieve a 1:1 magnification with better DOF. I got the same results that you have at around the 200mm FL. but as you can see that the DOF is much shallower as opposed to the dedicated macro. you increase the FL further and you'll get a much more shallower depth. yes, a flash could help a lil bit especially when you set the aperture at the smallest opening, but still the DOF area is just small to be considered usable.

a prime 135mm lens + diopter test would be another good experiment. since it is a fixed focal length lens, and the only adjustments to be made are the aperture opening and focusing distance, I could only assume that the IQ results and DOF would be very good. the aperture opening could be atleast wider than that of a telephoto zoom and focusing would be much more forgiving.

if you have a 135mm, maybe you could show us a result of that one as well.
08-13-2009, 05:14 AM   #34
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QuoteOriginally posted by Pentaxor Quote
no, it's not a 250. what I meant is that you should get a 1:1 magnification with a better DOF at 150. I guess you already did the test and saw what I meant. I mentioned the 100mm FL because that is where I got the best magnification coming from the 55-300 (though not 1:1) at infinity focus. the 150mm that I said is where you could achieve a 1:1 magnification with better DOF.
Yes, I did the test and saw that you were correct. I still don't understand where the smaller FL came from (Mark said 135 on a prime, you said 150 on the 55-300). Is it just from experience?

QuoteOriginally posted by Pentaxor Quote
a prime 135mm lens + diopter test would be another good experiment. since it is a fixed focal length lens, and the only adjustments to be made are the aperture opening and focusing distance, I could only assume that the IQ results and DOF would be very good. the aperture opening could be atleast wider than that of a telephoto zoom and focusing would be much more forgiving.
When I said I'd respond to the rest of your post after I did some testing, I meant that I would try the Raynox on the DFA 100mm. I did the shoot last night but I didn't keep notes and now I can't translate some of the results. I'll try again later with the 100mm macro, with and without the Raynox 150 and 250, but I'll start another thread to show the results. Putting a Raynox on a 100mm macro at close focus achieves very high magnification. I'm guessing about 2.5:1 with the Raynox 250. DOF is again very thin unless you use extremely small apertures.

08-13-2009, 05:30 AM   #35
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QuoteOriginally posted by newarts Quote
Here's what's going on I think. The effect of adding a diopter close-up lens to a another lens is to create a new lens with a different focal length. The formula is:

1/f_new_meter = 1/f_old_meter + diopter

So for a 210mm lens with a 4.8 diopter lens added, the focal length of the combination is 105mm.

The iris diaphram opening hasn't changed, but the focal length has; therefore the f-stop has changed. The new f-stop is:

F-stop_new=Focal_length_new/aperture=F-stop_old*Focal_length_new/Focal_length_old
or,
F-stop_new = 11*105/210 = 5.5

So the effective f-stop has dropped from 11 to 5.5!

for the same magnification, this drops the depth of field by the same ratio, 5.5/11 = 1/2; a factor of two!

I think this is in good agreement with your observation; with the Rayox the DOF is lower at the same magnification and nominal f-stop because the actual f-stop is much lower (because the focal length is decreased.)
Nice work Dave, that certainly seems to describe what's going on.

QuoteOriginally posted by newarts Quote
PS I guess a teleconverter will have the opposite effect on actual f-stop - adding a teleconverter will increase the dof (at the same mag & nominal f-stop on the primary lens.)
That's a fascinating statement. Can anyone confirm this? I don't have a TC, I'm waiting on the new Pentax to be released.
08-13-2009, 06:56 AM   #36
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Thanks Dan,

It turns out there's a simple formula for the f-number, N, of a primary lens with a diopter lens , D, attached.

The magnification change due to the diopter lens on a lens of focal length Fo is:

m=FoD

If the original f-number is No, the new f-number is:

N=No/(1+m)

In your case the magnification due to the diopter lens was about 1:1, therefore the f-number was changed by a factor of 1/(1+1)=1/2; this in turn cut the DOF in half.

This effect is real - I mean the f-number really is changed by the magnification factor - in your case when the aperture ring says the f-number is 16, the real f-number is 8, so don't worry about diffraction effects, just crank the f-number up to increase DOF.

Dave

Edit - for a Raynox 150 on a 300mm lens the f-number factor is about 2.5 - on a 100mm lens the factor is about 1.5 - easy numbers to remember if you use it on a 50 -300 zoom like I do.

Last edited by newarts; 08-13-2009 at 07:34 AM.
08-13-2009, 03:19 PM   #37
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QuoteOriginally posted by audiobomber Quote
Yes, I did the test and saw that you were correct. I still don't understand where the smaller FL came from (Mark said 135 on a prime, you said 150 on the 55-300). Is it just from experience?



When I said I'd respond to the rest of your post after I did some testing, I meant that I would try the Raynox on the DFA 100mm. I did the shoot last night but I didn't keep notes and now I can't translate some of the results. I'll try again later with the 100mm macro, with and without the Raynox 150 and 250, but I'll start another thread to show the results. Putting a Raynox on a 100mm macro at close focus achieves very high magnification. I'm guessing about 2.5:1 with the Raynox 250. DOF is again very thin unless you use extremely small apertures.
I did some initial testing with an FA 100 macro + diopter before. from the results that I saw, the magnification has increased significantly atleast about a 2:1 ratio and DOF is not that too thin but seems to have a normal shallow DOF at wider apertures. I didn't need to stop down that much inorder to get a deep DOF with the FA 100 macro and I also found the images to be sharp.

with the 55-300mm though, I noticed a big drop in aperture opening inorder to compensate for a deep DOF and experienced some light loss due to the nature of the zoom telephoto lens (adjusting it's FL, distance between glass elements inside), also not to mention about a substantial loss in IQ. the equivalent of such magnifaction to that of the FA100 is around 210mm for the 55-300.

I guess we need a premium glass (a prime) if somebody wants an excellent macro lens alternative. maybe a 77mm LTD or and 85mm could be very good candidates in the telephoto range. so the formula would be a premium glass + premium diopter lens. you would no longer need a dedicated macro lens but you know how much those two prime lenses cost.
08-15-2009, 10:37 AM   #38
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extension tubes and reverse adapter

just shot these two shots with 2 extension tubes adds up to 125mm and reverse adapter with M 28 mm f2.8 lens manual.(reverse lens mounted) shot with flash and M-mode, handheld and aperture f9, f11.... shutter 1/25 sec sr on.
Viewfinder is quite dim but visible.



nip of a pen, uncropped, not PP, original image fr camera.



The height of the letter JA is approx. 1 mm, non PP, uncropped too, orignal image from camera


The ants was taken with vivitar macro 105 with raynox 250 mounted. flash was fired, handheld.

Extension tubes does offer a lower cost into macro photography

marcus

08-24-2009, 07:48 PM   #39
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There was a really great discussion here. Thank you all for posting your thoughts, experiences, and examples. In the end I decided to give the Raynox 150 a shot. Actually, I also grabbed a lens to mate with it. I grabbed an 'excellent' Sigma 28-80mm F3.5-5.6 Macro from KEH. The price was good ($19) and the lens has favorable reviews, as well as being 1:2 magnification. I figure with the Raynox, it will put me right where I need to be.

Granted, I still would like a true macro 1:1 lens, I am only into this combination for about $70. Not a bad start.

Once I have the combo together, I will be happy to post some shots.

Joe
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