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08-24-2018, 01:57 PM   #961
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QuoteOriginally posted by marcusBMG Quote
I was surprised to see the rubinar wasn't listed GUB, so I listed it that's my lens in the pics. It's a nice one actually, with original case, filters etc. and cyrillic user manual/certificate.

The DoF calculations merely emphasise the tightness of the focus. The practical issue is seeing it, which IME I can't do well enough in my OVF's, only by using magnification in an EVF or on screen, and then millimetrically tickling the focus to try to nail it.
It just isn't easy with mirrors.
The rubinar for some reason is particularly ticklish, I find I'm to-ing and fro-ing a lot, and end up trying to land on a middle position (I wonder if there's a bit of slack in the helicoid - check - yes I think there is). The tamron is significantly better - more clear cut oof-in-oof as I move the focus.
I use Liveview and focus peaking. But the focus peaking is barely activated in the low contrast image and when you touch the lens to focus the movement upsets everything. It is interesting in the dof calculator when you push the Q out to 600metres where it should be for same magnification as K-1 the dof shoots out to over a hundred metres. That is probably the more correct scenario.

08-24-2018, 09:46 PM   #962
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I find the Pentax Q's "circle of confusion" of 0.005mm to be highly suspect, especially when compared to the other two.
08-24-2018, 10:45 PM   #963
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QuoteOriginally posted by cooltouch Quote
I find the Pentax Q's "circle of confusion" of 0.005mm to be highly suspect, especially when compared to the other two.
Yeah I was the same till I thought it through. The thing is this dof standard is based on an end product print of a given size. The Q sensor has to be magnified 6 times as much as the K-1 sensor to achieve this print size. .03 x 1 / 6 = .005
An extension of this is any lens on the Q will present with 1/6 of the resolution compared to itself on a FF. Hence why the Q is so hard on lenses.
11-19-2018, 08:28 AM - 3 Likes   #964
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Sigma 600mm f8. Performs ok in spite of blemished mirror. X-post with sigma lens club. samsung NX20 from RAW.





11-19-2018, 08:57 AM   #965
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QuoteOriginally posted by marcusBMG Quote
Sigma 600mm f8. Performs ok in spite of blemished mirror. X-post with sigma lens club. samsung NX20 from RAW.


Nice images!
11-20-2018, 12:15 AM   #966
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Alright, Marcus -- looks like you've got one of the good ones. I've owned three Sigma 600s so far -- still own two of them. The best was the one I bought new in 1984 (and sold in 1989, dang it). The worst is a late model one in EOS mount i bought a few years ago. I bought another one a few months ago -- an early one, even earlier than my original 600. Its image quality is pretty good -- not as good as my Tamron 500, but not too far off. Contrast is low with this lens, and I think it's because of a fine coating of dust on the interior surfaces. I plan to dismantle the lens, thoroughly clean it, and test it again. I remain hopeful. I'm thinking about bringing my poor performer to our local pro camera repair shop and see if it can be recolimated to get rid of the double images it produces.
11-20-2018, 06:39 AM   #967
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QuoteOriginally posted by cooltouch Quote
looks like you've got one of the good ones.
I guess so Michael - test pics of the neighbours chimney showed a tad sharper in fact than one of my tamron 500's. But boy the focus is ticklish. By way of comparison, a tele-tokina 600mm f8 I have been comparing it with focuses from 10m (cfd) to infinity in ~330 rotation. The sigma does the same in ~ 30 rotation!
I did moon pics with the tokina and my 31A+1.4x tc as well - results were all similar. I tend to find that with moon pics - it's more atmospherics etc differences between the lenses are evened out.


It's easy to open this lens up, just take off the rubber and peel off the tape to separate the focus so it comes off the helicoid (mark the point). The mirror is backsilvered like the tamrons so that dished any hope I had of being able to clean - the blemish (a peripheral ring of tarnishing/silvering deterioration) is permanent.
11-21-2018, 05:58 AM   #968
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Yeah, I've got the rubber ring off my focusing collar, just haven't taken things to the next step yet.

I'm puzzled by your comment about having only 30 degrees of focus rotation on your Sigma. My Sigmas' focusing ring rotation is almost as great as my Tamron's. The Tamron is almost 360 degrees, and my Sigma's is probably 340 degrees or so. I don't have one handy at the moment, but that's what I recall at least.

11-21-2018, 07:25 AM   #969
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QuoteOriginally posted by cooltouch Quote
I'm puzzled by your comment about having only 30 degrees of focus rotation on your Sigma
You can see from the pic how little rotation there is from 10m to infinity. Total focus throw is a bit over 180 so the 2m cfd is out of sight.
Mine seems to be a later example of this lens. This off-white one on ebay is, from your descriptions of the filter holder (metal), an early one. It looks the same re focus.

https://tinyurl.com/ydzbjk73
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Last edited by marcusBMG; 11-21-2018 at 07:31 AM.
11-21-2018, 10:16 PM   #970
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Okay, I follow you now. Most likely my Sigmas are the same way.

Regarding the white one at UK eBay, that is a later one. It's hard to see, but one of the middle photos just shows the black plastic tip of the filter holder. I have never seen an early Sigma 600 in any other color than gloss black. One interesting thing I discovered about my early Sigma is that it is noticeably smaller than the later ones. Probably about 4-5mm smaller in diameter compared to the later ones.
12-24-2018, 06:18 AM - 4 Likes   #971
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Time to add some photos from the stellar Tamron 500mm f/8:

Brolgas in Derby, West Australia




12-24-2018, 06:31 AM   #972
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QuoteOriginally posted by Ash Quote
Time to add some photos from the stellar Tamron 500mm f/8:

Brolgas in Derby, West Australia



Rather similar in appearance to North American Sandhill Cranes. I guess all of the cranes dance, too.
12-24-2018, 09:30 AM - 1 Like   #973
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QuoteOriginally posted by goatsNdonkey Quote
Rather similar in appearance to North American Sandhill Cranes. I guess all of the cranes dance, too.
Yes, they are a variety of crane, and they do the mating dance:
12-28-2018, 05:49 AM - 1 Like   #974
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Eagle in West Australia

Eagles at the water treatment plant, Derby:

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