[rvandenbrink]

I think I’m finally going to replace my old A series zoom that has been my macro (sort of) lens since forever. I’m debating between the 50 and 100. I know that the main difference is distance from the subject.
The question I have is: for the same shot, is there a difference in depth of field? Or is it a wash after you factor in the distance difference?

[photoptimist]

There's little difference in depth of field between the two focal lengths for macro magnifications. The whole "wide angles have deeper depth of field than telephotos" rule only applies to lower magnifications.

That said, a shorter focal length does encompass more of the (blurry) background behind the subject so the look can be quite different. Shots with the 50 will have more background objects than shots with the 100.

Another big issue with macro focal lengths is that it's a lot easier to get to high magnifications with a short focal length. A 50mm macro set for 1:1 and with 50mm of added extension tubes or bellows gets to 2X magnification. A 100mm macro set for 1:1 needs 100mm of extension tubes or bellows added to get to 2X magnification. High magnification macro (>3X) usually involves shorter focal length macro lenses to keep the camera-lens distance reasonable.

[UncleVanya]

A Guide to Working with Different Focal Lengths for Macro Photography

50mm Macro vs. 100mm Macro - PentaxForums.com

Links like these may help.

[kypfer]

My preference for a macro lens veers towards a longer focal length because of the more "natural" perspective, the reduced risk of ending up working in your own shadow and the less likelihood of distressing a live subject and having it fly/scurry off.
Inevitably … YMMV

[rvandenbrink]

Thanks all! With 35, 50 and 100 on the table, I ruled out the 35 since it’s apc-c only, and though I did do bellows and tubes back in the 70’s, I likely won’t go there again.
Anyway, this discussion has made the final choice a lot easier - likely I’ll pop for the 100 - plus that one is WR. We’ll see if the new 100 comes out before I’m ready to buy
Too bad that zoom macros appear to be a thing of the past, though I guess they were never really “real macro” lenses

[TwoUptons]

It really will come down to what you are shooting...

But there are loads of ways to do macro, and don't forget you can do several of them inexpensively...

I have a 50mm FA macro as my "main" macro lens, but I also have a FA 100mm f3.5 that was inexpensive for when longer lengths are better.
There's also bellows and extension tubes, which will work with loads of lenses; reversing rings and closeup lenses.

One of the most important things I read here on the forums (I'd read it before but it was only here that it sunk in) was that the lighting really drives the quality of the shot more than anything with macro (both the amount, how it is distributed, and how it is metered). That's also something to consider...

I'll also point out that software helps now in ways it never did before. Focus stacking is a magical thing...

-Eric

[tryphon4]

There's little difference in depth of field between the two focal lengths for macro magnifications. The whole "wide angles have deeper depth of field than telephotos" rule only applies to lower magnifications.

There's NO difference in depth of field between the two focal lengths for macro magnifications. Period.

Depth of field varies according to magnification, aperture and circle of confusion (the latter being a constant for a given sensor size). So focal length is nowhere in the equation.

Of course, bokeh varies according to focal length, for the same aperture and magnification, this is why I generally prefer a 100mm to a 50mm. I even prefer a 150mm to a 100mm but I find more difficult to achieve good macro portraits with a 150mm than with a 100mm.

My prefered macro lenses are:
1. Laowa 100mm F2.8 APO 2x Ultra-Macro
2. Irix 150mm F/2.8 macro
3. Bresser/Oshiro/Laowa 60mm macro F/2.8
4. Any Tamron 90mm macro
5. Sigma 180mm F3.5 APO EX DG IF macro (rare, expensive, somewhat hard to use)

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Last edited by tryphon4; 08-28-2022 at 01:42 PM.

[JensE]

Another aspect that drives my choice of macro lenses is whether I shoot pure macro sessions or cover both macro and non-macro shots such as documenting people and the small things they're working on. Using a 50mm lens often allows to use a single body (K-1) for the later, a 100mm lens is usually too long.

For exclusive macro sessions, I do prefer longer focal lengths (100mm+) as well because of the above reasons: light and lower chances to scare subjects away. Once the focal length gets longer than 100mm though, it becomes significantly more difficult to quickly locate your subject in the progressively smaller "(field of view) x (depth of field)" space as you increase magnification.

[mlag]

My quick summary:

• compare macro lenses for the same magnification ratio (like 1:1 for true macro) or search for a lens with a good ratio. The lens database on the forum shows this value for each lens.... the 1:1 macro means that your subject is in same as’life size projected on your image sensor, hence your subject should be smaller than the sensor, or the ratio can be lower for larger objects (1:0,3 for instance might work well on a large butterfly) or you just focus less close with your lens for larger subjects .
• magnification increases if you focus closer and for a zoom on the longer focal length. Unfortunately there are zooms where (close) focus distance changes over zoom range and then you have to find the sweet spot...
• wide lenses tend to be easier in (very) close focussing - centimeters sometimes - and tele’s tend to have less close focussing capabilities - even above several meters - Macro designated lenses are optimised for (improved) close focus, hence yield larger magnification than their average comparable focal lens equivalent.
• going too wide in focal length and too close might distort the image: too much magnification in center and less to the wide edge of image, going too long tend to flatten or compress the object.
• longer focal lengths decrease depth of field, a larger butterfly with a 200mm might fall outside usefull range (use an online dof calculator to check). But if you want macro and stay away more than 30 cm ( a feet) from a shy animal/insect you want 100 mm or more focal length....
• a magnifying 1,4x or 2x tele convertor does not affect (keeps) closest focus distance but increases magnification
• extensions tubes decrease closest focus distance and hence increase magnification (check online for macro extension tube calclators or formula) and are more effective on shorter focal length lenses. You will loose infinity focus, the effect is strong, sometimes you can only focus from nearby to a few meters on a tele (birds at modest distance might be too far...) or less on other lenses.

[Papa_Joe]

As tryphon4 allready has stated in macro phtography depth of field is not dependent on the focal length used, thus you can rule it out as a criteria.

More important is what for you need the macro abiltiy. As you used a Pentax A zoom lens you probably never got more than 1:4 ratio, that is what the so called zoom lenses had in the times then. If you are looking for a modern auto focus replacement for the occasional close up the 55-300 PLM might be a choice for you or the Tamron 70-200/2.8, which both give you about 1:3 ratio.

A true macro lens will have at least 1:2 ratio and AFAIK all the modern AF lenses have 1:1. If you are going to ratios around 1:2 and further up to 1:1 the distance between the front lens and the subject is the critical issue. Then you will be happy for every other mm of focal length. This is true for every object be it a ladybug in the field or a coin on the repro stand. For those ratios I would thus allways recommend a longer focal length, at least 90 mm.

However if you have a repro stand and are going to take duplicates of medium format slides 35 mm will be handy because at those ratios of about 2:1 the column is to short for a 100 mm.

Then there is the question of the secondary or main use. For portrait 100 mm on APS-C is a bit on the long side for example. And I really do not know, what I would do with a 35mm/2.8 on APS-C?

I myself own a 70 mm/2.8 macro from Sigma which gives a very nice portrait lens on APS-C and the more on full format, but which is on the short side for higher macro ratios. It is very nice for butterflys, but taking pictures of a ladybug will result in shadows from the lens not to be avoided.

[garywakeling]

Umm just a word of warning, the newer lenses lack an aperture ring which can come in handy when using the things you used to use , bellows and extension tubes, they are really handy to play with when using macro subjects and worth thinking about

[UncleVanya]

Then there is the question of the secondary or main use. For portrait 100 mm on APS-C is a bit on the long side for example. And I really do not know, what I would do with a 35mm/2.8 on APS-C?

I always wonder about this line of reasoning. On 35mm film at one time the common lens trio was either 28 / 50 / 135 or 28 / 50 / 85. The 85 was typically faster f2 or f1.4 vs the 135 at f3.5 or f2.8. But in both cases the longest lens in the trio was the lens used for portraits.

A 135/2.8 makes excellent head shots and good half body shots if you have enough room to back up y. A 100 macro on apsc is more like a 150mm equivalent which is a touch longer and less commonly available in the old days, but well within reason for portraits - particularly head shots.

The fact is I commonly use lenses 31mm to 200mm for portraits on apsc. I’ve have actually used a 15mm a few times as well as a 400mm for 3/4 heads shots (mostly Candids). My preferred lenses on Pentax APSC are the SMC DA 40 Ltd, SMC DA* 55, HD DA 70 Ltd, SMC FA 77 Ltd, and DA* 50-135. My DA 18-135 has taken some great portraits with careful background selection and subject placement (typically around 70-80mm).

IMGP0093 by -vanya_42nd-

IMGP0640-pp by -vanya_42nd-

IMGP1667-pp by -vanya_42nd-

IMGP3162_DxO by -vanya_42nd-

IMGP5112_DxO by -vanya_42nd-

IMGP59252_DxO by -vanya_42nd-

IMGP9089_DxO by -vanya_42nd-

IMGP8215_DxO by -vanya_42nd-

IMGP0435_DxO by -vanya_42nd-

[Papa_Joe]

I always wonder about this line of reasoning. On 35mm film at one time the common lens trio was either 28 / 50 / 135 or 28 / 50 / 85. The 85 was typically faster f2 or f1.4 vs the 135 at f3.5 or f2.8. But in both cases the longest lens in the trio was the lens used for portraits.

A 135/2.8 makes excellent head shots and good half body shots if you have enough room to back up y. A 100 macro on apsc is more like a 150mm equivalent which is a touch longer and less commonly available in the old days, but well within reason for portraits - particularly head shots.

The reason why longer focal lenghtes in general are not recommended for portraits is, that with more distance to the person being photographed the face looks flatter and personal features get lost. If you take into account, that the classic portrait is usually at least a brest and shoulder or half piece the resulting focal length will be something between 70 - 100 mm on full frame. That in mind a 135 mm will give you a headshot from about the same distance.

Of course that is a general recommendation and I would not suggest anyone to stick to that. I am shure you can take a good portrait with any lens.
As your impressive selection shows. Very nice pictures!

Then I have to admit there is a personal bias as well. I should have made that more clear in my statement. I prefer to shoot half person portaits or head and shoulder with lenses up to 50 mm (on APS-C). I allready feel unconfortable when I use my 70 mm for those.

[UncleVanya]

The reason why longer focal lenghtes in general are not recommended for portraits is, that with more distance to the person being photographed the face looks flatter and personal features get lost. If you take into account, that the classic portrait is usually at least a brest and shoulder or half piece the resulting focal length will be something between 70 - 100 mm on full frame. That in mind a 135 mm will give you a headshot from about the same distance.

Of course that is a general recommendation and I would not suggest anyone to stick to that. I am shure you can take a good portrait with any lens.
As your impressive selection shows. Very nice pictures!

Then I have to admit there is a personal bias as well. I should have made that more clear in my statement. I prefer to shoot half person portaits or head and shoulder with lenses up to 50 mm (on APS-C). I allready feel unconfortable when I use my 70 mm for those.

Thank you for your input. Conventional wisdom suggests flattening, but my own experience suggests it’s very minimal.

Without looking at Exif can you tell which of the shots posted used the DA* 200 on apsc? Those shots range from 31 to 200mm.

[Owltown]

I think I’m finally going to replace my old A series zoom that has been my macro (sort of) lens since forever. I’m debating between the 50 and 100. I know that the main difference is distance from the subject.
The question I have is: for the same shot, is there a difference in depth of field? Or is it a wash after you factor in the distance difference?

I shoot both 50mm and 100mm AF Pentax lenses. Evaluate what sort of macro work you'll be doing, as the super-short lens-to-subject distance with the 50 can cause lighting problems. Doing tabletop work with artificial light, the 50 sometimes casts its shadow on the subject - requiring me to reposition the lights and lose the effect I was after. This is not as much a concern in the great outdoors, where light is usually more uniform and multidirectional. BTW, I shoot a K-1.