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Forum: Pentax SLR Lens Discussion 06-26-2022, 09:35 AM  
Looking For a Macro
Posted By tryphon4
Replies: 27
Views: 1,479
Too many people still believe that depth of field varies according to the focal length. It is false! Period.
Depth of field varies according to enlargement (and according to aperture value, and circle of confusion, the latter being fonction of the sensor dimensions).

At a given enlargement, e.g., 1:1, you will get the same DOF with a 24mm, with a 50mm, with a 100mm, with a 180mm, etc.






Same enlargement, same DOF, different bokeh.

However, as the bokeh and the geometric distorsion will vary according to the focal length, a lens between 50mm and 100mm will generally be the best choice if you use an aps-c sensor.
Forum: Pentax Full Frame 02-28-2021, 01:35 PM  
Macro lens on K1 to digitize 645 B/W negs
Posted By tryphon4
Replies: 23
Views: 1,673
Purple Fringing
Forum: Pentax SLR Lens Discussion 01-16-2021, 02:55 PM  
Best zoom macro lens for Pentax?
Posted By tryphon4
Replies: 29
Views: 2,513
It is a zoom but it is NOT macro. There are several models with different optic formulas, mine (Sigma 70-200mm f/2.8 II Ex HSM Macro DG) goes to about 1:3.

I own one Sigma 180mm F3.5 APO EX DG IF macro, it is a very good macro lens but very expensive (and of course it is no more produced).

I also own one Irix 150mm F/2.8 macro, it is a very good macro lens too, and affordable (and it is still in production). Its bokeh is awesome.

By the way, there are cheaper options, for example if you own a PENTAX DA* 300mm F4 sdm ED [IF], you could buy a Nikon 6T close up, then you would reach 1:1 (about 1.1:1 if I am not wrong) and get a huge working distance: 28cm @ 1:1.

Irix 150's working distance is about 17.2cm @ 1:1.
Sigma 180's working distance is about 23.1cm @ 1:1.
Forum: Pentax News and Rumors 01-02-2021, 02:43 PM  
Laowa 100mm F2.8 2:1 Macro lens for k-mount
Posted By tryphon4
Replies: 439
Views: 51,457
Today, I received my lens, it is quite heavy but the construction is tough.

The A position is a bit weird: there is no locking. Anyways, it works so I can use modes different from M, great!

I measured working distance at 1:1 and 2:1 and found these values:

At 1:1, WD = 91mm (+/- 2mm)
At 2:1, WD = 73mm (+/- 2mm)

I estimate that the incertities are about 2mm (my equipment (rule, square) is not traceable to a standard calibrated according to ISO 17025 and there can be a small bias in my setup) .

Forum: Pentax SLR Lens Discussion 12-25-2020, 01:27 PM  
Older FA lenses
Posted By tryphon4
Replies: 12
Views: 960
I own one FA 35/2 and one FA 50/1.4, I love them.
FA 50/1.4 must be used with a hood in order to get enough sharpness between F/1.4 and F/2.8, practically I always use a hood with mine.
Forum: Pentax Camera and Field Accessories 12-22-2020, 12:42 PM  
Budget macro confusion
Posted By tryphon4
Replies: 80
Views: 3,742
Wow, already 3 pages about this subject!

Well, extension tubes can be a good solution but there are things to take into account.

First, there are cheap extension tubes and expensive ones. The bad news is that the cheaper ones will give poor results because the inside painting does not absorb reflected light as it should do.
A good set of extension tubes would be a "K type" set, with mechanical coupling for aperture automatism.
You can also find a "KA" type set with electric contacts but this kind of stuff is rather expensive.
The "KAF" type, enabling autofocus, is almost useless and way too expensive.

Second, be aware that an extension tube (or set or bellows) will always enhance the defects of the lens: if you can see CA without extension, you will see more CA with the extension. The same for purple fringing and MTF loss. In fact it is almost the same for a TeleConverter or for a close-up (or reversed lens).

Third, the good news is that you may never see the defects if you do not perform pixel peeping and if you resize your photos.

Fourth: high macro ranges (from 5:1 to 10:1) require low focal lenses (less than 35mm) if you want to keep enough sharpness. So, if you intend to get sharp photos with a lens and extension tubes, you will have to use an excellent lens not prone to diffraction (and fast apertures).

Last one (for the moment): A flash will be your best friend, because extension tubes are light-eaters.

When I started macro, I chose close-ups instead of extension tubes, it can give good results if the focal length of the lens is medium (about 100 to 200mm).

K100D, 15-55mm and close-up:

Now I rarely use close-ups or tubes, I prefer to use a dedicated macro lens :)

However, tripod is not mandatory, you can use extension tubes or close-ups without a tripod, but most of time a flash will be welcome.
Forum: Pentax Camera and Field Accessories 12-22-2020, 11:04 AM  
What happened to the polarizing filter?
Posted By tryphon4
Replies: 19
Views: 2,501
Yes, entropy cannot decrease. Isaac Asimov wrote an interesting novel about this subject.
Forum: Pentax Camera and Field Accessories 12-21-2020, 12:42 PM  
What happened to the polarizing filter?
Posted By tryphon4
Replies: 19
Views: 2,501
There are a variety of methods of polarizing light so it could be complicated to compare several polarizing devices:Physics Tutorial: Polarization
Forum: Pentax Camera and Field Accessories 12-16-2020, 10:53 AM  
What happened to the polarizing filter?
Posted By tryphon4
Replies: 19
Views: 2,501
Polarizing filters absorb light, they partially transform light into heat.
Consequently, their life is more or less short: more you use them, faster they deteriorate.
Forum: Pentax SLR Lens Discussion 11-29-2020, 01:52 PM  
Telephoto lenses for shooting tits : 10 lenses compared
Posted By tryphon4
Replies: 10
Views: 1,750
LensBeginner, PO is for "pleine ouverture", it means "wide open".
Forum: Pentax Full Frame 11-18-2020, 11:29 AM  
Silent Shutter
Posted By tryphon4
Replies: 14
Views: 1,499
I was not aware of this small detail... It is very interesting.
If global shutters had the same specs as rolling shutters, they could be interesting for video and for flash synchro speed.
Forum: Flashes, Lighting, and Studio 10-24-2020, 02:02 PM  
Flash for GR iii
Posted By tryphon4
Replies: 18
Views: 8,008
Yes, it works in P-TTL mode. The GRIII has a Pentax hot shoe, not a Ricoh one.
Forum: Troubleshooting and Beginner Help 10-17-2020, 02:04 AM  
Posted By tryphon4
Replies: 16
Views: 1,557
Mirror lenses lack sharpness, and their bokeh is generally ugly.
I own one 500mm F5.6, seldom use it.

You'd better buy a good zoom, or a vintage A* or FA* 300mm F4.5 and add a 1.4x teleconverter.

My DA* 300mm F4 and Pentax-F 1.7x AF Adapter make a great combo.
Forum: Photographic Technique 10-10-2020, 02:32 PM  
Macro Some questions regarding dof with different lenses / formats
Posted By tryphon4
Replies: 12
Views: 1,159
You are right, creamy was not the best word, I should have written "uniform" instead. English is not my main language, I sometimes make some mistakes.
Forum: Pentax SLR Lens Discussion 10-07-2020, 09:27 AM  
Good zoom lens for the K-1
Posted By tryphon4
Replies: 30
Views: 2,573
I own one Tokina 28-70 AT-X (non-PRO).

It is soft wide open but fine from F/4 (looks like spherical aberration).
However, it is a bargain because few people seem interested by this non-PRO lens.

So there are three drawbacks:
The AF sound can be a problem
It has a "vintage" look
It is soft wide open (but I may own a bad copy).

Here is an example @ 70mm F/2.8:

The TAMRON 28-75mm 2,8 XR seems to be a good lens too.
Forum: Flashes, Lighting, and Studio 10-01-2020, 01:17 PM  
Question about vivitar 285 zoom thyristor flash
Posted By tryphon4
Replies: 17
Views: 2,185
I own one vintage Vivitar 285 and several 283, all are high voltage flashs (about 250V) so a 285 would kill your DSLR.
You can use your 285 in wireless mode but not on the hot shoe and even not wired through a PC sync wire.

These flashs are very interesting because you can modify them in order to replace the removable light cell by a potentiometer, then you get a studio flash that you can calibrate:

IMGP5704 by Hervé Laville, sur Flickr
Forum: Troubleshooting and Beginner Help 09-26-2020, 12:23 AM  
Macro Lenses.
Posted By tryphon4
Replies: 26
Views: 2,625
I still own a K100D super, it was my first DSLR.

I started macro using the standard 18-55mm lens and a magnifying glass. This very basic setup can give good results:
Maya by Harvey LAVIL, sur Flickr

Several months later, I bought my first macro lens, a Cosina 100mm macro F3.5. It can reach 1:2 alone and 1:1 if you use the dedicated close-up.
Then I bought one 1.4x teleconverter and 2 extension ring kits, here is a setup enabling about 5:1:
bagues-allonges by Hervé Laville, sur Flickr

Later, I bought a Tamron 90mm macro (model 52B), my first Tamron. Then I bought (and sold) many other macro lenses.

I currently own 6 macro lenses from 60mm to 180mm, they reach 1:1 to 5:1, I love each one.

I sometimes revert a wide angle lens (35mm e.g.) and maybe add one or two extension rings.
I also can add a close-up to a telelens (the Pentax DA* 300mm F4 performs well if you use it with a Nikon 5T or 6T close-up).

To summarize, the possible setups are endless. You just have to choose a lens according to your needs and you can add

-bellows or extension rings if it is a short focal,
-close-up if it is a long focal.

You also may try microscope lenses or enlarging lenses, it is weird but it works:

objectif de microscope sur reflex by Hervé Laville, sur Flickr
Pentax K7, Zörk MFS, Rodenstock APO-Rodagon 50mm f2.8 by Hervé Laville, sur Flickr

Practically, insects and bugs prefer longer lenses because the working distance is longer. So 100mm to 200mm is a good range.

There are lots of topics about maco lenses over there, you can read them in order to make your choice.
Forum: Pentax Compact Cameras 07-06-2020, 01:16 PM  
ricoh gr ii vs pentax q7
Posted By tryphon4
Replies: 7
Views: 2,343
I do not own a GR II and a Q7 but I own a GR, a GRIII and a Q.

Q's sensor is a bit smaller than Q7's but it is not relevant, both sensors are very small.
Q's image quality is not amazing at all. Nowadays, I hardly use my Q because bokeh is never smooth and image quality is never excellent.

GR, GRII and GRIII use an aps-c sensor, it is another league, another world compared to Q's family.
Image quality is excellent, bokeh is smooth.
The only problem regarding GR's family is the fixed 28mm (24x36 equivalent) focal length: you cannot zoom in or out, you just can buy a converter in order to shoot at 21mm (24x36 equivalent) or you can crop in order to simulate a longer lens.

In a nutshell: Q is flexible but not so good, GR is excellent but rigid.
Hope it will help.
Forum: Pentax SLR Lens Discussion 07-02-2020, 10:37 AM  
Is the Pentax D FA Macro 100mm WR the best macro option out there for my K1?
Posted By tryphon4
Replies: 22
Views: 2,465
Same for me: I own macro lenses from 28mm to 180mm and choose the one I will use according to the purpose (I will not use the same lens for flowers at 1:10, insects between 1:4 and 1:1 and details between 2:1 and 5:1).

I will prefer my Bresser/Oshiro/no-name 60mm F/2.8 2:1 when a short working distance is acceptable. It is full manual, sharpness is rather good and bokeh is smooth.
I will choose my Mitakon 85mm 1:1-5:1 when I need huge working distance. It is full manual too.
If I need a compact lens, I will use my Tamron 90mm F/2.8 Di, it is close to the Pentax 100mm WR, except that the Tamron is not WR.
If I need AF and a huge working distance, my Sigma 180mm F/3.5 lens will be welcome.
When I want smooth bokeh and vibrant colors, my Irix 150mm F/2.8 will be the one ; it is WR too.
Forum: Pentax SLR Lens Discussion 06-05-2020, 01:32 PM  
APS-C Macro Lens
Posted By tryphon4
Replies: 39
Views: 3,551
I own a Panagor 90mm macro F/2.8, it is a good macro lens and its price is attractive.
Compared to a Tamron 90mm F/2.8 macro Di, the Panagor's working distance is longer, it is a plus in some cases. The largest flaw of the Panagor is CA, I see some chromatic aberration on my photos. The Tamron does not share this flaw.

Of course, a Pentax DFA 100mm macro is slightly better than the Tamron but I could never compare them.

I owned an old "adaptall" Tamron 90mm F/2.5 macro, built like a tank and rather sharp but it only reaches 1:2.

I currently own and use several macro lenses (mainly between 60mm and 180mm), and can say that 100mm is the best compromise in terms of focal length in macro if you aim to shoot living animals. Yet the bokeh is smoother using 100mm and above.

Here are some pics shot using the Panagor 90mm:

Forum: General Photography 04-04-2020, 12:33 AM  
CS mount varifocal CCTV lens usage in photography.
Posted By tryphon4
Replies: 5
Views: 698
A C-S lens could be used on a Pentax Q, the problem is to find a "C-S lens to Q" ring adapter.
There are plenty of "C lens to Q" adapters but I never found a "C-S lens to Q" one on €bay.

C mount register is 17.526mm, C-S mount register is 12.526mm, Q register is 9.2mm.
Camera Mounts Sorted by Register

You may want to 3D-print a custom adapter, then there is a useful link : C & CS Lens to PENTAX Q mount adapter by nameless911 - Thingiverse
Forum: Photographic Technique 12-17-2019, 11:08 AM  
Macro Another Macro option
Posted By tryphon4
Replies: 15
Views: 1,544
Well, it does not look so different from what is commonly used by macro fans.

For example, in 2011 I used this setup: Pentacon six lens (80mm F/2.8) on a "PK to Pentacon six" tilt adapter, step-down rings, reversed enlarger lens (Componon 28mm F/4)

You can easily reach 8:1 and more with that kind of setup, what is important is to use very good optics (sharp). In this case the Pentacon was not so good, using the reversed 28mm on long extension rings was preferable :)
Forum: Pentax News and Rumors 12-03-2019, 02:20 PM  
Mitakon 85mm 2.8 1X to 5X Macro Lens $499
Posted By tryphon4
Replies: 48
Views: 4,775
This lens seems to be very interesting!

The announced working distance at 1:1 (230mm) is similar to the Sigma 180mm macro F/3.5's working distance, huge!
The announced working distance at 5:1 is stellar: 95mm. For information, the "famous" Canon MP-E 65's working distance at 5:1 is 41mm only!
In fact it is hard to believe.
Forum: Pentax SLR Lens Discussion 12-01-2019, 07:41 AM  
Pentax macro lens
Posted By tryphon4
Replies: 44
Views: 2,428
The original 60mm F/2.8 2:1 macro lens is made and sold by Venus-Laowa.
However, there are copies of this lens with almost the same shape, they share the same optics and are sold under other brands: Oshiro or Bresser.

According to Laowa, the Oshiro's and Bresser's 60mm are copies, but I have no proof of that. The price is lower for the (potential) copies so I bought a copy (mine has no brand at all but the shape is the same than the Bresser).

Here is the Laowa:

Here is my "copy":

The common characteristics of Laowa, Oshiro and Bresser are:
- No "A" position on the aperture ring: If you set an aperture of F/16, you will compose your photo and focus at F/16, not wide open (and it may be difficult if you have no pilot lamp).
- 14 blades aperture
- same weight, height, diameter: about 500g, 70x95 mm
- same optics (9 elements, 7 groups)
-same minimum focusing distance: 18cm

This is the Venus-Laowa user review section: Venus Optics Laowa 60mm F2.8 2:1 Ultra Macro Lens Reviews - Venus Laowa Lenses - Pentax Lens Review Database

The Kuangren Kx 800 flash is compatible with any Pentax camera. It is fully manual: you separately adjust the power of the two heads.

It contains a led pilot lamp (with variable power), this pilot lamp is hugely useful when you close the aperture at F/8 and beyond.
Forum: Pentax SLR Lens Discussion 12-01-2019, 08:00 AM  
Pentax macro lens
Posted By tryphon4
Replies: 44
Views: 2,428
The working distance is an important characteristic from my moint of view, because insects can be very shy.

You can find below some working distances at 1:1, in centimeters:

As it is in French, I have to translate a point: the Vivitar 135mm Close Focus (real 135mm, reaches 1:2 alone) is here used with an extension ring set (650mm added), it is impressive but hard to use because it becomes a bazooka (see below, the last lens).

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