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Tamron SP f5.6 / 350mm (06B) mirror lens
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PostPosted: Sun Aug 08, 2021 4:27 pm    Post subject: Reply with quote
woodrim wrote:
You are probably stretching the usefulness of that mirror with that type of photography. You might do a tad better with a narrow spacer rather than the 1.4 TC. I have used a narrow extension ring on one of my 300mm mirrors to get closer to flowers but not for insects. A high mp sensor like yours will certainly help by having greater crop ability. In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.


The spacer would get me closer, which is not the point of using the lens. I have plenty of close-up/macro glass.

That idea of DOF and cropping is a myth.

It was a first try, the main problem being the lack of visible grasshoppers on that day. I didn't even get a good image (framing) with my EM-1 and regular macro lens.


PostPosted: Sun Aug 08, 2021 5:01 pm    Post subject: Reply with quote
...

Last edited by Blazer0ne on Tue Feb 22, 2022 5:55 pm; edited 2 times in total


PostPosted: Sun Aug 08, 2021 5:11 pm    Post subject: Reply with quote
e6filmuser wrote:
woodrim wrote:
You are probably stretching the usefulness of that mirror with that type of photography. You might do a tad better with a narrow spacer rather than the 1.4 TC. I have used a narrow extension ring on one of my 300mm mirrors to get closer to flowers but not for insects. A high mp sensor like yours will certainly help by having greater crop ability. In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.


The spacer would get me closer, which is not the point of using the lens. I have plenty of close-up/macro glass.

That idea of DOF and cropping is a myth.

It was a first try, the main problem being the lack of visible grasshoppers on that day. I didn't even get a good image (framing) with my EM-1 and regular macro lens.


Then what was the point that I missed?

And, I don't do myths.


PostPosted: Sun Aug 08, 2021 5:38 pm    Post subject: Reply with quote
woodrim wrote:


Then what was the point that I missed?

And, I don't do myths.


The point you missed (?) was that I can't use my 100-400mm on the A7r3.


PostPosted: Sun Aug 08, 2021 6:48 pm    Post subject: Reply with quote
woodrim wrote:
You are probably stretching the usefulness of that mirror with that type of photography.


My first reaction to that was no way! However, I have been trying some shots of cacti. With the same setup and working distance.

Even though I was sitting down, I still found it remarkably difficult to focus and the DOF seemed far shallower than I would expect at f8(ish).

The best of those were still a bit soft.

So you are probably right.

I was only trying the lens for this purpose because it had scarcely been used since I purchased it several decades ago.

I have other lenses, such as the Tamron 180mm Anniversary Edition which can do the job with a TC.


PostPosted: Sun Aug 08, 2021 7:19 pm    Post subject: Reply with quote
woodrim wrote:
e6filmuser wrote:
woodrim wrote:
... In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.

...
That idea of DOF and cropping is a myth.

...
And, I don't do myths.


I don't understand. Farther away, with less magnification, DOF is increased.


PostPosted: Sun Aug 08, 2021 7:34 pm    Post subject: Reply with quote
visualopsins wrote:
woodrim wrote:
e6filmuser wrote:
woodrim wrote:
... In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.

...
That idea of DOF and cropping is a myth.

...
And, I don't do myths.


I don't understand. Farther away, with less magnification, DOF is increased.


And closer with more magnification e.g cropping it is decreased, dramatically as you crop away more and more of the image.

I once believed that you could take a distant shot and retain that depth by cropping but if that were the case, every macro at, say, f11 would have the horizon sharp!


PostPosted: Sun Aug 08, 2021 11:48 pm    Post subject: Reply with quote
visualopsins wrote:
woodrim wrote:
e6filmuser wrote:
woodrim wrote:
... In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.

...
That idea of DOF and cropping is a myth.

...
And, I don't do myths.


I don't understand. Farther away, with less magnification, DOF is increased.


Yes, you do understand. Simple.


PostPosted: Mon Aug 09, 2021 2:07 am    Post subject: Reply with quote
woodrim wrote:
visualopsins wrote:
woodrim wrote:
e6filmuser wrote:
woodrim wrote:
... In fact, I wonder if you'd do better having the greater DoF from farther away and cropping.

...
That idea of DOF and cropping is a myth.

...
And, I don't do myths.


I don't understand. Farther away, with less magnification, DOF is increased.


Yes, you do understand. Simple.


And cropping to the same frame size (and viewing both identical frames from the same distance), increases magnification (the same amount), DOF is decreased (to be the same in both frames viewed from the same distance.)


PostPosted: Mon Aug 09, 2021 5:21 am    Post subject: Reply with quote
visualopsins wrote:


And cropping to the same frame size (and viewing both identical frames from the same distance), increases magnification (the same amount), DOF is decreased (to be the same in both frames viewed from the same distance.)


Thanks. I had just logged in to say precisely that. It is not the cropping that reduces DOF but what we then do with the cropped image.

I would love the above to be untrue. I shoot macro on most days of the year. I often have a FOV 3.5mm wide and am working with a DOF of around 1mm at f11 (set on lens).


PostPosted: Mon Aug 09, 2021 3:48 pm    Post subject: Reply with quote
I'm pretty sure we are arguing different points. Maybe I didn't express it clearly enough. My point is so simple it is silly to have to explain. Here are two pictures taken with the same lens and aperture. The first was up very close and did not include the flower petals in clear focus. The second was taken at a greater distance and thus did include the petals within the DoF. The second was cropped much greater and loses sharpness due to the limits of my sensor. If I had the pixel density of the A7RIII, it would hold up sharper than my 24mp sensor allowed but still demonstrates my simple point. While shooting yesterday with a friend whom I am mentoring, he was using his 28mm Close Focus lens and lamented that he couldn't get the whole flower in focus. There were two solutions; stop down significantly or back up. Both would change the bokeh characteristics but that is the trade-off.


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PostPosted: Mon Aug 09, 2021 4:02 pm    Post subject: Reply with quote
woodrim wrote:
I'm pretty sure we are arguing different points. Maybe I didn't express it clearly enough. My point is so simple it is silly to have to explain. Here are two pictures taken with the same lens and aperture. The first was up very close and did not include the flower petals in clear focus. The second was taken at a greater distance and thus did include the petals within the DoF. The second was cropped much greater and loses sharpness due to the limits of my sensor. If I had the pixel density of the A7RIII, it would hold up sharper than my 24mp sensor allowed but still demonstrates my simple point. While shooting yesterday with a friend whom I am mentoring, he was using his 28mm Close Focus lens and lamented that he couldn't get the whole flower in focus. There were two solutions; stop down significantly or back up. Both would change the bokeh characteristics but that is the trade-off.

...


Both images have identical DOF to my eyes.


PostPosted: Mon Aug 09, 2021 4:47 pm    Post subject: Reply with quote
I give up.


PostPosted: Mon Aug 09, 2021 5:12 pm    Post subject: Reply with quote
woodrim wrote:
I give up.
Like 1 small Smile


PostPosted: Mon Aug 09, 2021 5:22 pm    Post subject: Reply with quote
visualopsins wrote:


Both images have identical DOF to my eyes.


You did well, when the two examples are at different orientations, where different DOFs might be relevant. Smile
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