Search found 5938 matches

by Lou Jost
Sun Feb 18, 2024 7:21 am
Forum: Technical and Studio Photography -- Macro and Close-up
Topic: Debunking the high NA / coverslip correction myth
Replies: 73
Views: 32229

Re: Debunking the high NA / coverslip correction myth

This is very valuable info, please don't be put off by the misinterpretations. That's normal. I've been through it myself here. The forum members are intelligent and eventually misunderstandings will be cleared up! Rik, the graph you present surely refers to finite objectives, right? I can imagine t...
by Lou Jost
Fri Feb 16, 2024 11:47 am
Forum: Equipment Discussions
Topic: Sharpest aperture for a given macro lens
Replies: 35
Views: 1333

Re: Sharpest aperture for a given macro lens

here you can have a look on the test of my Sigma 105. A comparison of a 16x pixelshift reveals that at f2.8 the Sigma outresolves the sensor of a Sony A7R4/5 since the pixelshift shows much more details as a single frame :D http://www.photomacrography.net/forum/viewtopic.php?p=288434#p288434 Of-cou...
by Lou Jost
Thu Feb 15, 2024 3:37 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Reversed lenses--usefulness of electrical contacts to control aperture?
Replies: 11
Views: 461

Re: Reversed lenses--usefulness of electrical contacts to control aperture?

I have run out of extension tubes so I had to use stuff in the telecom scrapheap (pogopins). My spare extension tubes went into converting an old Canon Auto Bellows (FD mount) to EF lenses. Split in halves and connected by a cable. Sounds familiar? I can see from the links in your signature that yo...
by Lou Jost
Thu Feb 15, 2024 1:23 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Reversed lenses--usefulness of electrical contacts to control aperture?
Replies: 11
Views: 461

Re: Reversed lenses--usefulness of electrical contacts to control aperture?

I just cannibalized parts from an extension tube, and cut and soldered parts to minimize its thickness. I am lazy compared to you!
by Lou Jost
Thu Feb 15, 2024 11:54 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: Reversed lenses--usefulness of electrical contacts to control aperture?
Replies: 11
Views: 461

Re: Reversed lenses--usefulness of electrical contacts to control aperture?

I made an inexpensive connector to control the aperture and focus of reversed MFT lenses. I think these are definitely excellent lenses when reversed on a FF sensor for m >2. But it is relatively easy to skip the connector and just set the aperture with the lens attached to an MFT camera and the twi...
by Lou Jost
Tue Feb 13, 2024 5:55 pm
Forum: Equipment Discussions
Topic: Horsing around with EF 400mm DO II
Replies: 5
Views: 353

Re: Horsing around with EF 400mm DO II

"It is often stated that stopping the reversed lens down is not a good idea" Dick, I don't think any of us here would say that, except for very specific high-end lenses. Usually we do stop down the front (reversed) lens, though it should be better to put an aperture between the two lenses. The back ...
by Lou Jost
Tue Feb 13, 2024 5:50 pm
Forum: Equipment Discussions
Topic: New 2-5x 25mm macro from AstrHori, potentially sharper than the laowa?
Replies: 9
Views: 611

Re: New 2-5x 25mm macro from AstrHori, potentially sharper than the laowa?

I think this is potentially a very interesting lens and I hope someone careful, like Robert O'Toole, will compare it to the Laowa. Claims that it is just a copy of the Laowa are just false, as mentioned above. The optical diagram and the glasses used are very different. Form the specs, it certainly ...
by Lou Jost
Mon Feb 12, 2024 3:33 pm
Forum: Technical and Studio Photography -- Macro and Close-up
Topic: Perla Marginata (Stonefly)
Replies: 11
Views: 502

Re: Perla Marginata (Stonefly)

Do you have any special problems (and solutions) when shooting through water? What are you using?
by Lou Jost
Mon Feb 12, 2024 3:23 pm
Forum: Nature Photography -- Macro and Close-up
Topic: Miscellaneous creatures
Replies: 6
Views: 1172

Re: Miscellaneous creatures

Yes, that hairstreak rear-end is wonderful. As you said, the standard explanation is that this distracts a predator, making it think that the butterfly is facing backwards. The butterfly can easily escape a pounce at those tails. But your picture makes me wonder if perhaps something more is going on...
by Lou Jost
Mon Feb 12, 2024 3:17 pm
Forum: Technical and Studio Photography -- Macro and Close-up
Topic: Halyomorphis halys
Replies: 5
Views: 358

Re: Halyomorphis halys

Yes, it's very nicely lit. You've solved the hardest part. There are many ways to make a bellows or extension tube easier to focus in small increments. The best may be to put the whole assembly on a manual focusing rail. In that case you could even dispense with the bellows and use a rigid extension...
by Lou Jost
Wed Jan 31, 2024 1:35 pm
Forum: Macro & Microscopy Articles
Topic: Why and how are insects attracted to night lights
Replies: 5
Views: 353

Re: Why and how are insects attracted to night lights

It is nice to see empirical research on this mysterious subject, and their explanation is novel and interesting. I have my doubts though. My own kitchen window attracts moths, wasps, and rhinoceros beetles at night. The rhinoceros beetles in particular repeatedly crash head-on into the window, and m...
by Lou Jost
Tue Jan 30, 2024 4:03 pm
Forum: Technical and Studio Photography -- Macro and Close-up
Topic: some scales
Replies: 140
Views: 14977

Re: some scales

For short-lived subjects like fragile flowers, flash is very helpful, to avoid the continuous light source over-heating the subjects and causing them to wilt during a long stack. I had the "clever" idea of using a tiny plastic centrifuge tube as a vase to stand small flowers in, with wet cotton woo...
by Lou Jost
Mon Jan 29, 2024 12:16 pm
Forum: Equipment Discussions
Topic: microscope lens 10x
Replies: 37
Views: 1995

Re: microscope lens 10x

Please study Chris S's comment above!! It looks like you may not have read or understood it. It was important.
by Lou Jost
Sun Jan 28, 2024 5:33 am
Forum: Equipment Discussions
Topic: New Rayfact Lenses at Japan Trade shown in 2023
Replies: 11
Views: 692

Re: New Rayfact Lenses at Japan Trade shown in 2023

The specs are actually disappointing: it looks like it is only corrected for green light! In that case cheap second-hand stepper lenses come quite close to those specs.
by Lou Jost
Fri Jan 26, 2024 3:42 pm
Forum: Equipment Discussions
Topic: ultra macro suggestions beyond 10x -- cheaper but ok objectives to play with? Sony aps-c
Replies: 36
Views: 1864

Re: ultra macro suggestions beyond 10x -- cheaper but ok objectives to play with? Sony aps-c

One unusual option for long working distance with high NA is to work underwater. I have a 40x 0.80 water dipping Nikon objective that has a working distance of 2mm. That's very high for such a big NA. These are expensive though. I just mention it in case someone is wrestling with the compromise betw...