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09-20-2010, 07:48 PM   #31
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QuoteOriginally posted by Unsinkable II Quote
Losing nearly 1.5 stops of light that you thought you were paying for is an issue.
Yeah, but are you really paying the use of f/2.8 in macro shots? No, you're paying for it at "normal" distance, and the ability to take macro shots at all.

QuoteQuote:
Also, keeping with the Sigma 70mm "F2.8" as an example, it's not even F2.8 until 10 feet, meaning you don't get the full DOF advantage with headshot portraits.
Well, it might not be f/2.8, but it's not f/4.8 either. I'm guessing it's still f/2.9 at portrait distance, and doesn't really start to lose aperture until you get within a foot or two.

09-20-2010, 08:53 PM   #32
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QuoteOriginally posted by Laurentiu Cristofor Quote
Which dictionaries are you referencing? My Wordsworth doesn't have "lense" - only "lens".

Also, a quick search online produces this definition (lense - Wiktionary):


I like etymology, so I'd like to find out more about this spelling form.
Hey me too!! Love trying the NYT xword puzzle every day...not always successful but it sure is fun.

As for "lense" I had a link somewhere for a paper someone did on the etymology of lense/lens and I was in the "lens" camp but it had all the details supporting it was more modern spellling. It was really quite facinating and in the end the thread I was involved in...you would like it for sure...we had a fun time.

I am too worn out tonight, I started a new med for my RA and it nausea is kinda icky plus it has me run down since I took my first dose this afternoon....but I promise to follow up tomorrow sometime or even tonight is I find a third wind.

BTW, if you like the study of language I am sure you have watched the movies "Word Play" (wil Shortz is EVIL incarnate) and Helvetica...both differetn but both cover things some of us took/take for granted or never considered. If you haven't seen either or only one give them a try.
09-20-2010, 11:46 PM   #33
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QuoteOriginally posted by brecklundin Quote
BTW, if you like the study of language I am sure you have watched the movies "Word Play" (wil Shortz is EVIL incarnate) and Helvetica...both differetn but both cover things some of us took/take for granted or never considered. If you haven't seen either or only one give them a try.
Thanks for the suggestions - Let's take this discussion offline to not divert this thread. I'll send a pm.
09-20-2010, 11:55 PM   #34
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QuoteOriginally posted by RioRico Quote
A couple quick points (yeah, I'll be brief for a change).

With any non-reversed lens, the closest focus (MWD) is the lens' focal length. This is easy to test. Put any lens on tubes (or bellows) of various lengths. See how close you can focus. My rough test is to hold a ruler against the screen of this laptop, then put my K20D in LiveView and slide it down the ruler until the screen is in focus. That gives me the MWD. With any reversed lens, the working distance (min/max) is the registration (mount to frame distance), which for Pentax lenses is ~45mm, under two inches.

There are SOME macro lenses whose maximum aperture does NOT change with magnification. I mentioned this here some time ago and was told that Nikon stole, er borrowed the design from somewhere. The iris blades open or close with focus, giving a constant f/4 or whatever. Apparently there hasn't been a great demand for this. Tsk.

The Konica macro Hexanon 55mm f3.5 has a mechanical connection between focus and apperture that compensates for the loss of light with increasing magnification by gradually opening the apperture. You don't maintain a constant apperture, but you maintain a constant exposure. Some of the micro Nikkors (micro is macro for Nikon, somewhat confusing) have a similar mechanism, and I believe they where inspired by Konica (who where one of the main actors on SLRs back then long before the Canikon dominance where established).

Besides this obscure information I'd like to point out that this discussion is somewhat meaningless. In practise the DOF is so thin in macro applications that in almost all cases you will want to stop down as much as possible to get enough DOF to fit the whole subject (bug or whatever) within the DOF. The only valid point is to what degree it may be more difficult to manually focus because the viewfinder gets darker and darker. It will be some difference between manual focus a f2.8 or an f5.6 lens.

09-21-2010, 03:52 AM - 1 Like   #35
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The f-number of a lens is a well defined thing. It is the lens' focal length divided by its aperture opening.

A non-internal-focus (old fashioned) lens's focal length and aperture do not change as you move the lens towards or away from the camera to bring things into focus. The light intensity on the image plane changes, but the ratio of focal length to aperture does not.

Things are not so simple with a modern internal focus (IF) lens; for such a lens, focusing is achieved by moving some of the lens' internal elements which changes the focal length of the lens. Therefore, if the iris diaphragm opening is not simultaneously adjusted, the actual f-number will change as the lens's internal elements are shifted to bring an image into focus on the image plane.

But say you had placed the IF lens in question on a bellows and focused by moving the whole lens with respect to the camera; in this case the internal focus mechanism is not used hence the f-number does not change.

By convention, the f-number written on a lens barrel refers to the focal length divided by the aperture diameter when the lens is focused at infinity. Nikon or Canon or whoever is not cheating when they say that a particular IF lens has an f-number of 2.8.
09-21-2010, 04:10 AM   #36
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I work with both the Pentax FA*200mm f/4 ED IF and Sigma 180mm f/3.5 APO IF EX DG series lenses and with these focal lengths subject isolation and shallow DOF are a pain in the soft parts, I often have to use the DOF stacking technique. It kind of ticks me off that no one has ever made a tilt macro lens. I prefer larger formats e.g 4X5 large format with a 67 rollfilm reducing back for macro work because the ability of Large format cameras to manipulate DOF.

I think this demand for shallow DOF goes a bit far in photography these days and it is starting to irritate me.I'm not picking on the OP, I'm just saying that continuously trying to get shallow DOF can be counter-productive and sometimes detrimental to obtaining the best image quality.
09-21-2010, 04:15 AM   #37
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QuoteOriginally posted by Nick Siebers Quote
Like throwing a 50mm on a bellows - the size of the aperture is the same, but you need a lot more light or longer exposure to make up for the light lost to extension.
It's not the extension, but the magnification. A subtle point, but read on...

QuoteQuote:
One of the positive aspects of the "close-up filters" is that they do not reduce light in this way. (The others are that they are easy to carry, and easy to put on. Downside - mostly they suck :-)
A simple uncorrected +diopter closeup meniscus does indeed suck. Corrected closeup glass like the Raynox gems don't suck so much. The best such 'adapter' is a stacked reversed lens. Put a 105mm lens on-camera. Add a thread-reversal ring. Screw a 35mm lens onto that, reversed. Magnification is PRIMARY / SECONDARY, or 105/35 = 3x. And even though no extension has been added, you STILL lose over 4 f-stops of light. AP=NP*(M+1) so if the primary and secondary are both at f/2.8 (nominal aperture, NP), the apparent aperture (AP) is 2.8*4 = 11.2, or ~f/11.

QuoteQuote:
Reversing a lens is also useful for good macro with somewhat less light loss, but I don't know the math.
Reversing a lens alone provides a fixed close working distance and a flatter image field, not magnification. With a single lens, magnification comes from extension. A reversed lens with a deep front inset will magnify more than a reversed lens with a shallow inset, because the inset acts as extension. And because a reversed Pentax lens has a working distance of around 45mm (under two inches) you're necessarily VERY CLOSE to a subject, and so fill the frame with its image.
09-21-2010, 07:29 AM   #38
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It may be physics and it may be unavoidable, but it does have an effect. I was out in a field taking some photos of butterflies last night in dim light with flash. At some point the dark screen just ended the macro portion of my shooting even with mf. If I hadn't had F2.8 as the max aperture to start with, I would never have gotten half the shots I got. That's the moral of the story. Faster macros are a must for the wild.

09-21-2010, 04:05 PM   #39
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QuoteOriginally posted by Digitalis Quote
I work with both the Pentax FA*200mm f/4 ED IF and Sigma 180mm f/3.5 APO IF EX DG series lenses and with these focal lengths subject isolation and shallow DOF are a pain in the soft parts, I often have to use the DOF stacking technique. It kind of ticks me off that no one has ever made a tilt macro lens. I prefer larger formats e.g 4X5 large format with a 67 rollfilm reducing back for macro work because the ability of Large format cameras to manipulate DOF.

I think this demand for shallow DOF goes a bit far in photography these days and it is starting to irritate me.I'm not picking on the OP, I'm just saying that continuously trying to get shallow DOF can be counter-productive and sometimes detrimental to obtaining the best image quality.
Have you thought of trying to mount a MF lens, like the Pentax 67 135mm macro, in front of a DSLR? It should leave enough space to make some sort of tilt mechanism.

The artistic thin DOF fetichists forget that most of us most of the time keep on strugling to get enough DOF to cover the whole subject, be it a whole landscape or a dragonfly. The fast lenses I have (e.g. Sigma 20/1.8, FA35/2, FA50/1.4, A*85/1.4, A*135/1.8) I have mainly to be able to shoot in low light and to enjoy the bright viewfinder they give me. The ability to shoot with razor thin DOF is only on third place.

Wish I had any of your ~200mm macros. Tried to buy the Sigma new, but turned out it is now out of production and stock in K mount. Cheating with three combo's to get reach: Tamron SP90/2.5 + 1.4x/2x converter (auto exposure, but 2x is quite dificult to focus manually) / DFA100 macro + 1.7x converter (auto exp and AF, works OK) / old high end Canon FD lens 200mm f4 macro 1:1 on glass less adapter (best IQ of these combos and fastest, but manual everything...but I got it for almost nothing). Dreaming of the A* or FA*200 mm macros. Only thing that would make me consider giving up the A*135/1.8.
09-21-2010, 04:15 PM   #40
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Douglas:

I shot the Sigma 180mm macro for over a year and it is a wonderful hunk of glass. But I would buy the 150/2.8 if I bought another long Sigma macro. Not sure I would want the new 150 with OS but the previous 150/2.8 was a super sharp lense and a lot lighter than the beastie of the 180/3.5...still the 180/3.5 was FUN, especially with a reversed 24-60/2.8 on the end of it... my Frankenmacro lense with up to ~9:1 mag ratio with the 24-60 set to 24mm...and ~3:1 at 60mm. To me that was part of the fun of a longer macro, getting into the hyper-macro world. Had I stayed with Canon I would have bought their MP-E 65/2.8 which is a 1x-5x macro only lense. I think some jewelry shots would have been super and unique with that MP-E. And at the time it could be had under $600...now? dunno but I doubt it's that low though given it's limited appeal odds are it might still be close.
09-21-2010, 06:15 PM   #41
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QuoteOriginally posted by Douglas_of_Sweden Quote
I have mainly to be able to shoot in low light and to enjoy the bright viewfinder they give me. The ability to shoot with razor thin DOF is only on third place.
I own the FA31 and SMCP-K 50mm f/1.2 and (The leica noctilux 50mm f/1.0 )I am well aware of the advantages of such fast lenses all i'm saying is that people sometimes take this obsession with shallow DOF too far.

QuoteOriginally posted by brecklundin Quote
...a lot lighter than the beastie of the 180/3.5
You think the Sigma 180mm f/3.5 EX DG is heavy? Try hauling around a Nikon D3s with a 400mm f/2.8 ED IF VR Lens attached - That is heavy.

I only work with longer Macro lenses because with the kind of photography I do, shorter macro lenses would be a serious limitation. The sigma 180mm f/3.5 is one of a few macro lenses that actually has a tripod collar, which just happens to be able to support my sigma 100-300mm f/4 APO EX DG. I consider a tripod collar to be essential for macro work, because you can change from horizontal to vertical easily. Additionally they enhance stability. all current 100mm f/2.8 Macro lenses save for the canon 100mm f/2.8 L IS macro do not have tripod collars and that ticks me off..

Last edited by Digitalis; 09-21-2010 at 06:27 PM.
09-21-2010, 06:50 PM   #42
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QuoteOriginally posted by bdery Quote
So no one is loosing any photon in the process, but the convenient ratio we photographers refer to as f-number does change.
A lot of photons are lost. Think of a 50mm lens on a bellows. The further you move the lens away from the sensor, the higher the magnification. The latter is achieve by letting the lens create a bigger image circle while still using only a small centre part of it. All the photons in the bigger image circle that don't make it on the sensor are lost.

Most macro lenses work according to the very same principle. That's why they increase in length that much when close focusing.
09-21-2010, 08:42 PM   #43
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QuoteOriginally posted by Class A Quote
That's why they increase in length that much when close focusing
Except when they are internally focusing lens designs E.G Sigma 180mm f/3.5 APO EX DG and Pentax FA*200mm ED IF Macro

I don't understand why people don't get why you lose so much light at closer focusing distances. In the darkroom, when we adjust the height of the enlarger we always have to recalculate the exposure because the light source is further away. When large format photographers extend the bellows further than the focal length we are using we have to calculate the light loss.
09-21-2010, 08:53 PM   #44
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QuoteOriginally posted by Digitalis Quote
I own the FA31 and SMCP-K 50mm f/1.2 and (The leica noctilux 50mm f/1.0 )I am well aware of the advantages of such fast lenses all i'm saying is that people sometimes take this obsession with shallow DOF too far.



You think the Sigma 180mm f/3.5 EX DG is heavy? Try hauling around a Nikon D3s with a 400mm f/2.8 ED IF VR Lens attached - That is heavy.

I only work with longer Macro lenses because with the kind of photography I do, shorter macro lenses would be a serious limitation. The sigma 180mm f/3.5 is one of a few macro lenses that actually has a tripod collar, which just happens to be able to support my sigma 100-300mm f/4 APO EX DG. I consider a tripod collar to be essential for macro work, because you can change from horizontal to vertical easily. Additionally they enhance stability. all current 100mm f/2.8 Macro lenses save for the canon 100mm f/2.8 L IS macro do not have tripod collars and that ticks me off..
hahahaha.....too funny....Dude, I have RA and some days can hardly use my hands anymore but as recently as 2-years ago I used to lug around around 70lbs of gear including my 17" laptop, water, lunch, folding stool, 055xprob, 40D, sometimes a 5d I would borrow, 180/3.5, the Bigmos (150-500) and half a dozen other lenses for 8-12hrs/day in my large NG photo Explorer backpack all because I had no idea what I wanted to shoot when I could still get out and walk every day just took a few extra vitamin-V's....and still the way the girlie boys around here whine about lense weight I felt I should mention the Sigma 180/3.5 is a heavy lense at a bit over 2lbs without the collar & nearly 3lbs with the collar....I mean most of these sorts here whine about 2oz either way.

I mean if you wanna get into a pissing contest that is...
09-21-2010, 09:41 PM   #45
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QuoteOriginally posted by brecklundin Quote
most of these sorts here whine about 2oz either way.
Each to his own. At age 84 my grandfather was hauling around his 8X10 view camera in his 90's he downsized to 5X7 because he needed to carry more lenses with him. I have used his 8X10 and if more people had that experience, I don't think they could complain so much about camera form factors and ergonomics.

The 8X10 my grandfather used was an Ebony and needless to say it is a superbly constructed camera.
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