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06-08-2010, 06:09 AM   #76
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excellent work bjorsa!

06-08-2010, 06:22 AM   #77
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QuoteOriginally posted by bjorsa Quote
I use a expert 300/4,5 and a raynox dcr-250 and get 2,93:1-2,35:1 and focus at 11 cm from the front lens
Here a shoot at 2,7:1 on a small cherry shrimp (uncropped)

Kindly bjorsa
The portions that are in focus are great, but I would have liked to see more of the creature in the focus plane. What aperture did you use? I find that diopters need a smaller aperture to equal the depth of field of a macro lens at the same magnification.

Maybe luck1''s book has some math to show this?
06-08-2010, 07:57 AM   #78
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For the depth of field calculation you could use this site Online Depth of Field Calculator and this formula to calculate the combined focal length which is in that book. combined focal length = 1000/((1000/focal length) + diopter). You need also focusing distance which you have to measure for each combination.
raynox 250 has 8+ diopter on a 300 mm focal lenght you get combined focal length of 88 mm. Just put in the numbers, but the depth of field at this magnification will be small, even at f/16
06-08-2010, 08:20 AM   #79
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QuoteOriginally posted by TOUGEFC Quote
Have you tried using the 50prime and mount the 28prime reverse onto it? Its a nice small setup for 1.8:1
I have used the 28mm f/3.5 reversed without primary to get 2.1:1. There are simple adaptors that consist of a k mount and a filter thread to mount the lens directly to the camera. As the M28/3.5 has a 49mm filter thread, and I had the 52mm reverse adaptor, I used a 49>52 filter adaptor which gave a very small amount of additional extension. The 50mm is unnecessary, only the different adaptor is there.

06-08-2010, 08:29 PM   #80
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a couple questions:

How much magnification is achieved with a 50mm reversed on a set ofextension tubes?

If I buy a PTTL cable for my flash will I not have to wait ~4 seconds between shots due to the onbaord charging up? Its making stacking shots incredibly difficult.
06-09-2010, 01:54 AM   #81
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I used f22 so it was with max dof
Kindly bjorsa
06-09-2010, 04:32 AM   #82
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Well I solved my focus stacking issue...


5 images stacked using my M 50mm F/1.7 reversed taped on extension tubes. My flash was on camera with basically my take on Rense's flash diffuser... pictures tomorrow

I can take several images in a relatively quick manor now which is a HUGE help. There are some focus gaps, but hey its 4 AM in my area and im shooting handheld so needless to say im not at my prime
06-09-2010, 07:10 AM   #83
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QuoteOriginally posted by yeatzee Quote
a couple questions:

How much magnification is achieved with a 50mm reversed on a set ofextension tubes?

If I buy a PTTL cable for my flash will I not have to wait ~4 seconds between shots due to the onbaord charging up? Its making stacking shots incredibly difficult.
P-ttl isn't going to work with most extension tubes, the exception being those like the Kenko that have the A contacts. With the exception of the *ist D, DS DS2 non of the Pentax dSLR bodies support ttl flash either.

06-09-2010, 08:05 AM   #84
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QuoteOriginally posted by yeatzee Quote
If I buy a PTTL cable for my flash will I not have to wait ~4 seconds between shots due to the onbaord charging up? Its making stacking shots incredibly difficult.
How would a cable change the recharge time for a flash?
06-09-2010, 08:12 AM   #85
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QuoteOriginally posted by audiobomber Quote
How would a cable change the recharge time for a flash?
I think the poster intends to not use the on board flash at all by using a cable rather than wireless mode. With the cable, he can use P-TTL without enabling the on board flash. It makes perfect sense to me.
06-09-2010, 08:15 AM   #86
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QuoteOriginally posted by Canada_Rockies Quote
I think the poster intends to not use the on board flash at all by using a cable rather than wireless mode. With the cable, he can use P-TTL without enabling the on board flash. It makes perfect sense to me.
He still want be able to use p-ttl flash unless the extension tube has the A contacts. That's the whole point of stacking lenses where the one on the camera is an A type lens because p-ttl requires A contacts and K-7, K200d can NOT do ttl flash.
06-09-2010, 08:38 AM   #87
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QuoteOriginally posted by Blue Quote
He still want be able to use p-ttl flash unless the extension tube has the A contacts. That's the whole point of stacking lenses where the one on the camera is an A type lens because p-ttl requires A contacts and K-7, K200d can NOT do ttl flash.
You are absolutely correct, Blue - but I was replying directly to the question of how using a cable could eliminate the recycle time required by the on board flash. The need for an A lens as the primary is a given.
06-09-2010, 08:54 AM   #88
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QuoteOriginally posted by Canada_Rockies Quote
I think the poster intends to not use the on board flash at all by using a cable rather than wireless mode. With the cable, he can use P-TTL without enabling the on board flash. It makes perfect sense to me.
There may be some confusion in terms here. To me, a Pentax 540 would be an onboard flash when it's mounted in the hot shoe. A 540 is not onboard when it's used remotely, whether by wire or wirelessly. The pop-up is not an onboard flash, it is an inboard flash.

Anyway, that doesn't directly relate to my point. My Sigma 530 Super takes four seconds to recharge, about as long as a Pentax 540 and twice as long as the built-in on my K20, so I don't see where the pop-up flash is causing a delay.
06-09-2010, 09:05 AM   #89
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QuoteOriginally posted by audiobomber Quote
There may be some confusion in terms here. To me, a Pentax 540 would be an onboard flash when it's mounted in the hot shoe. A 540 is not onboard when it's used remotely, whether by wire or wirelessly. The pop-up is not an onboard flash, it is an inboard flash.

Anyway, that doesn't directly relate to my point. My Sigma 530 Super takes four seconds to recharge, about as long as a Pentax 540 and twice as long as the built-in on my K20, so I don't see where the pop-up flash is causing a delay.
When working at macro distances, the recycle time of the 540 is very short. I would think your Sigma would be able to recharge in much less than four seconds when used at macro ranges. The built in flash has a much longer recycle time when used as a controller than the 540 has at these short distances. The cable allows use of the 540 without the built in flash to run the control sequence. At macro distances this will speed things up. The number of flashes that occur is reduced to exactly two - one pre-flash and one exposure flash. All the back talk between the two flashes is removed. Although the back talk series is a fraction of a second, it is still a finite amount of time that delays the ability to take the additional shots to use the focus stacking. With moving subjects, this might be significant.
06-09-2010, 09:31 AM   #90
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QuoteOriginally posted by Canada_Rockies Quote
You are absolutely correct, Blue - but I was replying directly to the question of how using a cable could eliminate the recycle time required by the on board flash. The need for an A lens as the primary is a given.
That's the real advantage to the cable, getting the flash off the camera regardless if it is being used in p-ttl or manual.
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