Crop from 75 to 90 mm in Lr?

[vladik]

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I have a 2/75 Cron. For my Leica M 240 that I am very happy with, but lately G.A.S. descended on my soul. I started looking at 4/90 Minolta M mount that I can get for reasonable amount of dosh (GAS is not that serious). Next I have two options, walk close to my subject that is not always possible, the second one is to crop in Lr. Here is where I would like you to help and advise me. Here is my calculation: 75 mm lens is 83% shorter then 90 mm lens, thus difference of 17%.  Lr indicates that photo taken with 75 mm is 5976 x 3992 pixels. If I crop to 4960 (5976 -17%) and 3313 (3992 -17%) would it give me a image size taken with 90 mm lens but reduced to 16.4 MP? I thank you for any constructive advice in advance.

[jlindstrom]

Hi Vladik,

 

Little detail correctio first: 75mm is 83% of the length of the 90mm and thus 17% shorter. You had the right idea, but it came out little wrong..

 

But yes, your logic is correct and it will result in a 16.4 megapixel cropped image. The perspective of the image is little different than with a 90mm, but I doubt many will notice if you don't tell :-)

 

Also your 75mm focuses 30cm closer than the 90mm APO and is around 100g lighter. I would probably just crop and be happy.

 

Compared to new 90mm APO you just saved 2 person trip to somewhere warm to take photos!

 

//Juha

[jaapv]

Err... perspective is independent of focal length and is determined solely by subject distance.

[jlindstrom]

yeh, wrong choice of words there.. should think twice before writing anything. What I actually was trying to say is that even though you get similar field of view to what you would get from a 90mm lens, you also get the character of a 75mm meaning distortions etc are different.

 

Luckily at the tele end of things the changes are not as apparent, as say using a 25mm lens and doing 2x crop to get to 50mm.

[Echo63]

I cant help with the math, but the 90m rokkor is a pretty nice lens, and cheap !

 

I think mine was just over $300 AUD landed in australia (from japan)

Its pin sharp, and almost mint, a few tiny little wear marks on the focus knurling.

The f4 can be a little limiting in lower light

 

Just do it, a bargain in the world of M glass (even non-leica M glass)

[Schrödinger's cat]

I would like to add my appreciation for the 90mm/f4 lens.  Before acquiring the Leica 90mm macro it was my absolute favorite for travel.  It fits in a pocket, is very sharp,, and carries a very affordable price.  You will absolutely be happy with the lens.

[MarkP]

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If you really do want a 90mm lens you might find that however good the 4.0/90 Rokkor/Leica-C, after the 2.0/75 APO-Summicron they are a disappointment.  GAS will determine that no sooner will you buy the 4.0/90 Rokkor that you will pine for a better lens.

 

You perhaps should consider, GAS-budget allowing, a 2.0/90 APO-Summicron or 2.8/90 Elmariit-M or

the 4.0/90 Macro-Elmar (my choice for a 90):

http://www.l-camera-forum.com/topic/175185-in-praise-of-the-4090-macro-elmar-m/

[CheshireCat]

Since you have the APO 75/2, don't waste your money on a 90mm lens, and especially on the APO 90/2.

 

I had the APO 90/2 and replaced it with an APO 75/2, a superior lens in every way.

I don't mind cropping to 90mm equivalent on the M240, I even crop to 135mm equivalent on the A7R2.

 

And no, you won't see any difference in character between a native 90 shot and a 75 cropped to 90-equivalent.

[jaapv]

You might see a minuscule difference in DOF.

[vladik]

I cant help with the math, but the 90m rokkor is a pretty nice lens, and cheap !

 

I think mine was just over $300 AUD landed in australia (from japan)

Its pin sharp, and almost mint, a few tiny little wear marks on the focus knurling.

The f4 can be a little limiting in lower light

 

Just do it, a bargain in the world of M glass (even non-leica M glass)

 

 

Hi Echo63, I just place an order for a mint one from Hong Kong, bit more then AUD 300, but given the condition I am happy with my purchase. (Lower AUD against USD and an AUD 30 shipping cost did not help.) Vlad.

[menos I M6]

You do buy a 90 mm for either the extended reach over 75mm (not being able to close the gap by moving closer), or the different perspective it provides at same framing.

More selective DOF is not a consideration, given you think about buying a 90/4 and have already a very fast 75/2.

 

If you are able to move your feet, the extended reach of the 90mm is not much of a consideration for you it seems.

 

So your last important argument to think about is the different perspective a 90mm delivers over a 75mm.

 

This also is determined A LOT by what you intend to photograph with either lens.

 

Close up range is not much of a consideration too, as your 75mm is focussing very close already (and is beautifully corrected for close up performance too). A 90mm (apart from Leica's own 90/4 Macro-Elmar) won't give you any more performance here.

 

There is one last practical consideration when thinking Leica M and 75mm vs 90mm:

- the 90mm frame is displayed considerably smaller than the 75mm frame in a standard (.72 / .68) viewfinder, hence a 75mm might be more useful for some, while others might prefer the shape of the 90mm frame over the 75mm frame (you can easily see this for yourself by moving the frame pre-view lever)

[Exodies]

You might see a minuscule difference in DOF.

 

 

Is this due to the enlargement or something else? 

 

And y'all keep banging on about cropping to 90 or cropping to 135; don't you crop to the scene?

[epand56]

You can also have a Leica Elmar-C 90/4 for less than 250 USD if you keep searching. Don't know if it's equal or better than the Rokkor, but I would never give mine away. Its a sharp, light, little monster.

[CheshireCat]

Is this due to the enlargement or something else? 

 

At the same subject distance, a 90/2 will have a slightly smaller DoF than a 75/2 cropped to 90 equivalent.

This is due to the larger diameter of the aperture.

To have the exact same amount of blur of a 90/2, you should use a 75/1.7.

Anyways, like Jaapv said, at f/2 there's very little difference.

 

And y'all keep banging on about cropping to 90 or cropping to 135; don't you crop to the scene?

 

Yes, obviously.

What we mean is that a 75 allows capturing the same scenes you typically capture with a 90 or 135 (the latter only on 40+ MP sensors). Where "allows" means you still have an acceptable image resolution.

[Herr Barnack]

If you crop from 24mp to 16.4 mp, you will also erode image quality of the printed image at larger print sizes.  If you want to maintain 300 dpi for print quality, a 16.4 mp file will have a smaller 300 dpi maximum size than a 24 mp file.  That is why I always strive to do my cropping in the viewfinder rather than in post processing.

[Jeff S]

 

There is one last practical consideration when thinking Leica M and 75mm vs 90mm:

- the 90mm frame is displayed considerably smaller than the 75mm frame in a standard (.72 / .68) viewfinder, hence a 75mm might be more useful for some, while others might prefer the shape of the 90mm frame over the 75mm frame (you can easily see this for yourself by moving the frame pre-view lever)

 

Lever only on the M-P, not his M240.

 

Alternatively, he might prefer using a magnifier, especially with the 90.

 

Jeff

[CheshireCat]

If you crop from 24mp to 16.4 mp, you will also erode image quality of the printed image at larger print sizes.  If you want to maintain 300 dpi for print quality, a 16.4 mp file will have a smaller 300 dpi maximum size than a 24 mp file.  That is why I always strive to do my cropping in the viewfinder rather than in post processing.

 

One more reason to have a 40+ MP sensor.

[adan]

Keep in mind that the 90mm frame lines, since the 1980s redesign to add 75 and 28 lines, really show about a 105mm field of view. So if you get a 90, you will STILL be cropping about 15% in Lightroom, in order to get the composition you saw in the framelines.

 

While some do not like the 75 lines (confusion with 50mm lines, or too vestigial) - they are much more accurate in terms of what will be in the final picture, at most distances.

[Jeff S]

Keep in mind that the 90mm frame lines, since the 1980s redesign to add 75 and 28 lines, really show about a 105mm field of view. So if you get a 90, you will STILL be cropping about 15% in Lightroom, in order to get the composition you saw in the framelines.

 

 

 

Is this the same regardless of the change from 1m (e.g., M9) to 2m (e.g., M8.2 or M240) frame line optimization?

 

Jeff

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Hallo,

Look here: Leica M

[adan]

The 2m setting is better - for a given value of "better." When I tried a 240, I still got a lot of unexpected dead space in 90mm shots, around what I though I had framed. And less waste space with the 75. At landscape distances.

 

I've never figured out why the 90 lines changed so much - I suspect it has to do with the "stencil" or mask of thin metal, that hides or reveals the lines when lenses are changed (or the selector lever is operated). My suspicion is that there had to be a certain amount of solid metal between the linear cutouts, to prevent the stencil from just falling apart, and thus the 90 lines had to be squeezed a bit smaller "away" from the 75mm lines.