Using ext tubes


derek897

Link Posted 29/08/2018 - 08:39
I do a fair bit of macro shooting, using mostly bellows of late, but also with ext tubes.
My question is, what focal length should be input for the SR to function correctly.
So, for example, if using 50mm of tubes, should the focal length just be increased by 50mm or is there a different formula because of the magnification factor ?
Bellows then produce a different dilemma as it has varying degrees of extension.
Is it a case of trial and error, whatever works for you or is there an actual system for working it out ???
Any thoughts
I know what i like, If not always why.

LennyBloke

Link Posted 29/08/2018 - 09:18
It's a good question and one that I've never seen answered fully. It "feels" right to input the focal length as the lens length (e.g. 50mm) plus the length of the tube - so a 50mm lens plus a 25mm tube would be 75mm (or as close as you can get) in the SR settings. But, if you consider that a typical manual focus macro lens can extend in physical length by a significant amount then this calls this technique into question. A 100mm macro at infinity can be physically much shorter than at closest focus!

It has been discussed before that SR may not work so well for macro lenses as for others, so maybe the old fashioned techniques of high shutter speed (above the equivalent focal length of the lens), a tripod, or flash - plus turning off SR may work out better

I'll watch for suggestions/answers to this one
LennyBloke

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bforbes

Link Posted 29/08/2018 - 09:32
Is this the answer. link
Barrie
Too Old To Die Young
.
Pentax K1 K5-IIS K-01 K20D A50/2 A50/1.7 DA10-17 DA18-250 DA18-135 DA18-55 DA300 DA40 DA50-135 DA50-200 DA55-300 DA70 F35-70 DFA150-450 FA20-35 FA100 FA135 FA35 FA28 FA43 FA50 FA77 K55/1.8 M135/3.5 M200/4 M28/3.5 M28/2.8 M40/2.8 Q 01 02 MX-1 I-10 Sigma 15 24 105 180 8-16 10-20 17-35 17-50/2.8 24-70 400/5.6MF Tamron 70-200/2.8 17/3.5MF 24/2.5MF 28/2.5MF 90/2.5MF


http://www.pentaxphotogallery.com/artists/barrieforbes

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Algernon

Link Posted 29/08/2018 - 10:26
The best way is to try it. Take a few shots with say 50mm, 75mm, 100mm etc. set in the camera at shutter speeds where blur is likely. See which setting provides the most keepers.

It's probably related more to magnification than actual length. Similar to Electronic First Shutter Curtain or EFSC which is worse at high magnifications.

http://www.robertotoole.com/blog/2014/01/28/electronic-first-shutter-curtain

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

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coker

Link Posted 29/08/2018 - 10:42
If you're using flash Derek, which I'm presuming you would be, would the flash duration not be short enough to negate any camera shake, within reason?
I've found that any blur caused by shake is more likely to be "fore & aft", rendering the image out of focus, rather than "shaken".

Roger
The more I look, the more there is to see!

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derek897

Link Posted 29/08/2018 - 10:57
Not as easy a question to answer as it would first appear.
Most of my proper macro shooting is done with flash, so to be honest I am not really concerned about shake while using flash, as I think my technique is giving me pretty decent results, or at least results that I am happy with.
Although I have wondered about the question for a while, I just added the amount of ext to the fl of the lens, and in the case of the bellows, I just picked a mid point and used that, and that has worked for me, up till now.

This has cropped up from using tubes without flash, trying to preserve the natural light and shade, flash isnt an option for me, at least not without getting into a setup that just becomes off putting.

So just to clarify, no flash being used, although the answer, whatever it is, should be the same.
I know what i like, If not always why.

derek897

Link Posted 29/08/2018 - 11:04
2 examples, not the best of examples but you might see what I mean.
Will have to follow through to flickr to magnify the shots.


_IMG3160ed2sm by dr.shutter, on Flickr


_IMG3197ed2sm by dr.shutter, on Flickr
I know what i like, If not always why.

Algernon

Link Posted 29/08/2018 - 12:11
SR won't make any difference at 1/200th and 1/320th sec. It's around 1/25th sec. that it works best.

If you can get 1/200th only tests will tell if it's providing any benefit.

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Last Edited by Algernon on 29/08/2018 - 12:14

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derek897

Link Posted 29/08/2018 - 12:19
I didn't know that it didn't really work at higher shutter speeds.
I kind of guessed that it didn't really matter at really high shutter speeds. But figured that it should even at 1/300th ish.

I'm learning already 😁
I know what i like, If not always why.

Algernon

Link Posted 29/08/2018 - 12:20
On second thoughts using the 1/f rule anything up to 200mm would be sharp at 1/200th so no need to test. Improvement would be minimal and you shouldn't get any shake.


--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

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bforbes

Link Posted 29/08/2018 - 12:25
Algernon wrote:
On second thoughts using the 1/f rule anything up to 200mm would be sharp at 1/200th so no need to test. Improvement would be minimal and you shouldn't get any shake.


--

should that be 1/(fx1.5) if it's a Pentax aps-c camera
Barrie
Too Old To Die Young
.
Pentax K1 K5-IIS K-01 K20D A50/2 A50/1.7 DA10-17 DA18-250 DA18-135 DA18-55 DA300 DA40 DA50-135 DA50-200 DA55-300 DA70 F35-70 DFA150-450 FA20-35 FA100 FA135 FA35 FA28 FA43 FA50 FA77 K55/1.8 M135/3.5 M200/4 M28/3.5 M28/2.8 M40/2.8 Q 01 02 MX-1 I-10 Sigma 15 24 105 180 8-16 10-20 17-35 17-50/2.8 24-70 400/5.6MF Tamron 70-200/2.8 17/3.5MF 24/2.5MF 28/2.5MF 90/2.5MF


http://www.pentaxphotogallery.com/artists/barrieforbes

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derek897

Link Posted 29/08/2018 - 12:33
Maybe user error on my part then.
Mmm will try again tomorrow morning if conditions are similar.

However the question still remains around what the fl should be for Sr to work correctly
🤕🤕🤕
I know what i like, If not always why.

bforbes

Link Posted 29/08/2018 - 13:09
If you accept that calculation to determine a lenses focal length, then I don't think adding extension tubes makes any difference to the focal length you should dial in.

e.g.
1/100 + 1/100 = 2/100 = 1/50
1/150 + 1/50 = 2/100 = 1/50
i.e. if you add to the distance between the lens and the sensor you reduce the distance between the lens and the object by the same amount.
Barrie
Too Old To Die Young
.
Pentax K1 K5-IIS K-01 K20D A50/2 A50/1.7 DA10-17 DA18-250 DA18-135 DA18-55 DA300 DA40 DA50-135 DA50-200 DA55-300 DA70 F35-70 DFA150-450 FA20-35 FA100 FA135 FA35 FA28 FA43 FA50 FA77 K55/1.8 M135/3.5 M200/4 M28/3.5 M28/2.8 M40/2.8 Q 01 02 MX-1 I-10 Sigma 15 24 105 180 8-16 10-20 17-35 17-50/2.8 24-70 400/5.6MF Tamron 70-200/2.8 17/3.5MF 24/2.5MF 28/2.5MF 90/2.5MF


http://www.pentaxphotogallery.com/artists/barrieforbes

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Algernon

Link Posted 29/08/2018 - 13:26
bforbes wrote:
Algernon wrote:
On second thoughts using the 1/f rule anything up to 200mm would be sharp at 1/200th so no need to test. Improvement would be minimal and you shouldn't get any shake.


--

should that be 1/(fx1.5) if it's a Pentax aps-c camera

Derek is using a K-1, but to be exact with APS-C the 1.5 factor should be included, but being a rule of thumb and people's own vibrations being different 1/f should be OK. Magnification of the final image also matters.

In all the testing I've seen they alter the FL of the lens so that they can compare different formats so 200mm APS-C would be recorded as a 133mm/130mm
--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Last Edited by Algernon on 29/08/2018 - 13:29

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johnriley

Link Posted 29/08/2018 - 13:52
Magnification is a major factor with shake. using Love View, just watch the vibration with ultra close up and long telephoto images. It needs a good 10 seconds to settle down.
Best regards, John

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