[sterretje]

maybe this has been answered already, but does anyone like the manual focusing ring on either the 100wr or the da 35 2.8?

For macro, I like it a lot on the DFA100WR. For tele, it's too sensitive (smallest change already has a big effect); but it's forgiven as it's a macro lens.

[newarts]

Both 1:1 macros can produce the same maximum magnification, but I vaguely recall that there is a difference in depth of field when you compare two 1:1 shots at the same settings. My guess is that a shorter focal length would have more DOF if all other settings are equal, as a tradeoff for its shorter working distance.

In theory (and in practice) for equal exposure times (ie. same effective f-stop & iso) DoF for closeups depends only on magnification.

However, subject isolation will depend on focal length - long focal length usually allows better isolation (less apparent DoF) like Dave said.



That's a cracker box in the background..

[dh4412]

so, which of these shots is better? i like the detail of the flower in the 50, but the background blur of the 90.

[RioRico]

so, which of these shots is better? i like the detail of the flower in the 50, but the background blur of the 90.

'Better' is for you to decide, eh? We can make a blurrier BG with the 50 by repositioning the lens and subject slightly, by pushing the BG further away. We can also get a nice blurry BG by adding a close-up adapter to a standard 50mm lens.

[newarts]

'Better' is for you to decide, eh? We can make a blurrier BG with the 50 by repositioning the lens and subject slightly, by pushing the BG further away. We can also get a nice blurry BG by adding a close-up adapter to a standard 50mm lens.

I think that bigger, blurrier background is usually easier for long focal length lenses.


The above matrix of photos nicely illustrates the effect of focal length choice on subject isolation. The longer length lens usually makes it easier to angle the shot to make a big, fuzzy background which usually helps subject isolation.

Adding a closeup adapter decreases focal length so the background would typically look more cluttered with objects that are not very out-of-focus.

[RioRico]

Good, illustrative matrix of DOF effects.

Adding a closeup adapter decreases focal length so the background would typically look more cluttered with objects that are not very out-of-focus.

Adding a closeup adapter drastically reduces the focus distance and DOF so that the background is VERY out-of-focus. Try it.

[newarts]

Good, illustrative matrix of DOF effects.

Adding a closeup adapter drastically reduces the focus distance and DOF so that the background is VERY out-of-focus. Try it.

At the same magnification and exposure time (ie. constant effective f-stop) DOF does not depend on focal length. Background stuff will appear smaller for the wide angle lens case and because it is smaller appears to be less out-of-focus. Look at the left column in the following image.


Look at the tower in the background just to the right of the subject critter.

Here's the same photos showing that the tower images are in a sense equally out-of-focus. The inset in the left photo is the tower's image in the right photo enlarged to match the size on the left.


In practice I find it easier to isolate a subject using a longer focal length lens, macro or not.

[RioRico]

I think we're talking at cross-purposes here, and not focusing on closeup usage. A +dioptre closeup adapter reduces both the focal length and the focus distance. The focus distance reduction is much more drastic and has more effect on DOF than does the focal length change.

Let's say that I have a 50mm lens, with a focus range of 50cm-infinity and a strength of 1000/50= +20dpt, and I screw a +5dpt adapter onto it. The combined focal length of the system is 1000/(20+5)= 40mm. But the focus range drops to about 16-20cm. The small increase of DOF from the shorter focal length is overwhelmed by the dramatic drop of working distance, 2.5-3x closer.

Another example: Suppose I have a 100mm lens of 1000/100= +10dpt and focus range from 1m-infinity. I put the +5dpt adapter on it. System focal length is now 1000/(10+5)= 66.66mm but focus range is down to 16-20cm again. I'm working 10-15x closer, with much thinner DOF.

Closeup adapters have much more effect on longer than shorter lenses. Take a 25mm lens of 1000/25= +40dpt and focus range of 25cm-infinity. Put that +5dpt adapter on and we have a system of 1000(40+5)= 22.22mm and focus range of 16-20cm. We've hardly affected the focal length, focus range, or DOF at all. It's not worth the effort.

[normhead]

OK, I have another question... Tess and I are looking at a 35 macro, we already have a Tamron 90 macro, and it's a great lens, but she hogs it. We have a 21 and a 50, I was thinking the 35 would be a good prime to complete the collection... and give me a macro to fool around with while she has the 90... so what's the problem with the 30 macro?

[RioRico]

so what's the problem with the 30 macro?

Problem #1: No existe! There ain't none. Search the lens databases and you'll find no 30mm macro lenses, just 24-28-35mm.

Problem #2: Some 24mm and 28mm lenses are labeled 'macro' but really only go to 1:4 or less magnification. I've had a couple where the front element pulls out a little for closeups, but these are really close-focus lenses, not macro.

Problem #3: At greatest magnification, you're working VERY close to the subject. A non-reversed lens can focus no closer than its focal length. Thus for real macro shooting you'll be 24-28mm from subject to the lens' optical center.

Ah, a 35mm macro is another story. Pro: It's easy to fill the frame in a small workspace. Con: You're still working very close for good magnification. But for a mix of close and not-so-close work, the DA 35/2.8 Ltd macro is a fine lens. It's also around US$500. Ouch.

My experience: All my 'macro' lenses are totally manual, in 40-50-90mm. For really close AF (or at least A-type) shooting, I put AF or A-type lenses on deglassed A-type 2x TCs, or I use a Raynox DCR-250. The TCs are about 25mm thick, so one of them behind an A-type Toyo 28/2.8 nearly reaches 1:1 (but way too close!) and two of them behind the FA50/1.4 do reach 1:1. These setups are not edge-to-edge flatfield sharp. But those TCs cost me US$15 each and those setups are fine for shooting non-flat subjects.

[newarts]

I think we're talking at cross-purposes here, and not focusing on closeup usage. A +dioptre closeup adapter reduces both the focal length and the focus distance. The focus distance reduction is much more drastic and has more effect on DOF than does the focal length change.......

In this discussion it is important to be precise on just what it is we are comparing. I specified that magnification be held constant.

I'm completely aware of the optical effects of close-up adapters on focal length, DoF, working distance, etc.

The exact, complete DoF equation for macrophotography is:

DoF = 2 C Neff /m^2 where the effective f-stop, Neff = N(1+m/p) & p is the pupil magnification ratio (Exit.pupil/entrance.pupil)

Note that for a constant exposure time, Neff is what matters, not how lenses, tubes, or whatever were arranged to get a particular Neff & magnification; eg. there is no focal length effect.

Subject isolation is a different matter. Even for close-ups, smaller focal lengths see more background and what is seen is smaller than it would appear with a longer focal length lens - smaller images appear to be more in-focus than the same image enlarged.

Here's my standard example showing that effect. The DOF is the same for both photos - I think the cracker box in the background is more distracting with the shorter focal length macro lens.


I'll try to make a higher mag example soon.

[Arn]

For about $100 you could get an old Tak 50 (or other length), and some extension tubes and/or a reversing ring, and see if you like macro before spending a bunch on a great 100 WR. I'm still saving!

[newarts]

For about $100 you could get an old Tak 50 (or other length), and some extension tubes and/or a reversing ring, and see if you like macro before spending a bunch on a great 100 WR. I'm still saving!

Ah, but the difficulties of working with an old Tak 50 (or other length), and some extension tubes and/or a reversing ring will likely influence whether you like macro.

That's why I recommend starting with a good close-up attachment on a long automatic zoom lens - no juggling tubes on & off & no messing with manual flash or setting apertures.

With a Raynox DCR 150 adapter on a DA 55-300 zoom you just pop on the adapter, frame the photo & press the shutter button.

[dh4412]

how is the raynox dcr adapter used? does it screw on to the cap threads or ? and what does it do? thanks could it be used on a dfa 100?

[newarts]

how is the raynox dcr adapter used? does it screw on to the cap threads or ? and what does it do? thanks could it be used on a dfa 100?

The Raynox DCR 150 close-up lens comes with a clip-on arrangement that allows one to just snap it onto a 52-67mm filter ring so you'd have to either add a 49-52mm step up ring to your D FA100's 49mm filter ring or remove the Raynox from its clip-on thing and use a 49-43mm step-down ring to screw the Raynox into your lens.

It would extend your D FA's range of macro magnification to about 2:1. The results should be excellent macros; here's some shots with the Raynox 150 on a DA 55-300 posted by Beregeded today. I'd expect performance with the D FA 100 Macro to be at least as good.


https://www.pentaxforums.com/forums/lens-clubs/74221-raynox-macro-club-23.html#post1709155