Latest activity

AlanF · Apr 6, 2026

Xpenelas said:
No, a speed booster does the opposite, got a bigger image circle of the lens and concentrate it on the little sensor. Crop sensor gets the direction of a teleconverter, ditching the exterior part of the image circle and expand that on the bigger sensor.

With the modern sharper glass and camera vignetting corrections we are getting lighter and smaller lenses doing just that, reducing the image circle that goes trough the diafragm.

You are 100% wrong. A speed booster reduces the size of the image circle, as stated by @Bob Howland . If it increased the size, it would spread the light over a larger area and be a speed reducer. A speed booster works by reducing the focal length of a lens.

danfaz · Apr 6, 2026

fox40phil said:
But Canon better release something for Wildlife along the R7ii!

I intend to pair the R7II with my 100-500. Don't think much else would be needed for me.

Tom R5R7 · Apr 6, 2026

Show me a 400 mm f/4 lens that has a front element less than 100 mm in diameter and I'll show you a 400 mm lens that is smaller than f/4. If the entrance pupil is only 75 mm, assuming you still have a 400 mm lens, you have a 400 lens of approximately f/5.3. The f/stop is basically the focal length divided by the pupil. That is the mathematical definition of f/stop.

Here's a handy calculator...

F-Stop Calculator: Focal Length, Aperture Diameter, and F-Stop & Formula Online Calculator Ultra

Incidentally, in terms of the exposure calculation the f/stop is what it is. In terms of depth-of-field (or the shallowness thereof), the sensor size/format plays a role. That is why some people say that an f/4 lens on an APS-C camera is the equivalent of f/6.3 or 6.4 on a full frame camera. The exposure isn't different, but the apparent depth of field is.

fox40phil · Apr 6, 2026

4.0 is really sad…. Back in the days I wanted this EF 17-55 2.8 soo Hard…
This plus IS would be a premium Apsc lens! They could do it!

But Canon better release something for Wildlife along the R7ii!

Del Paso · Apr 6, 2026

I know from my own experience that even a "slight" modification of a product, in, my case, replacing a belt-drive with a chain -drive can take lots of time and even a huge amount of money, spent in modifying machinery, tooling, training staff, calculating cost, testing, informing, etc... etc...
For Sigma, it is not simply about paying licensing fees, adapting software and replacing the bayonet.
And, the article on (hugely biased and Sony friendly !) PhotoTrend was, in my opinion, more than vague...Nothing concrete!
I may add that I am more than happy with Canon's RF lens range, hoping for a few missing ones like TS and 24-70 II and 35mm f/1,2.
Sure, I wouldn't mind having more 3rd party choices and understand why some reasonably criticise Canon. Not speaking of the aggressive Sony trolls with their redundant and silly Canon-doom statements...
Yet, even in EF times, I've never bought Sigma or Tamron lenses. Only Zeiss (20mm f/2,8), since Canon's UWA were for a long time underwhelming.
I just expressed my personal and very subjective opinion.

Xpenelas · Apr 6, 2026

Bob Howland said:
What do you mean by "reducing the image circle"? That is what a Metabone or Meike speed booster does. That is why you have to use a FF EF lens with APS-C RF body. I have one from each manufacturer and use them regularly with my 150-600 f/5-6.3 Sigma Sport lens. That lens effectively becomes a 106-426 f/3.5-4.5. Then the 1.6X APS-C crop gets applied by my R7.

No, a speed booster does the opposite, got a bigger image circle of the lens and concentrate it on the little sensor. Crop sensor gets the direction of a teleconverter, ditching the exterior part of the image circle and expand that on the bigger sensor.

With the modern sharper glass and camera vignetting corrections we are getting lighter and smaller lenses doing just that, reducing the image circle that goes trough the diafragm.

Xpenelas · Apr 6, 2026

AlanF said:
What lighter and smaller telephotos does Nikon make for their crop cameras? They have done their best to make lighter weight ones for full frame, but they haven't made any of them as smaller and lighter versions for crop because not even they can get around the laws of optics.

Nikon is getting lighter and smaller telephotos reducing image circle and correcting vignetting on processing. Just go further and you have more.

Bob Howland · Apr 6, 2026

Xpenelas said:
No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

What do you mean by "reducing the image circle"? That is what a Metabone or Meike speed booster does. That is why you have to use a FF EF lens with APS-C RF body. I have one from each manufacturer and use them regularly with my 150-600 f/5-6.3 Sigma Sport lens. That lens effectively becomes a 106-426 f/3.5-4.5 but only covers an APS-C sensor..

AlanF · Apr 6, 2026

Xpenelas said:
So, you know more than Nikon's lens engineering. Go ****** yourself.

What lighter and smaller telephotos does Nikon make for their crop cameras? They have done their best to make lighter weight ones for full frame, but they haven't made any of them as smaller and lighter versions for crop because not even they can get around the laws of optics.

danfaz · Apr 6, 2026

Xpenelas said:
No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

neuroanatomist · Apr 6, 2026

Xpenelas said:
No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

So you don't understand optics and lens design, but you know more about marketing lenses than camera manufacturers? Lol. In the heyday of ILCs before smartphones clobbered the market, 90% of ILCs sold were APS-C DSLRs (and there were nearly 3 times as many ILCs sold per year as there are now in this 'recovering' market). Where were the EF-S and DX ≥400mm lenses then? There weren't any then, for the same reason there aren't any now. Physics.

A teleconverter reduces the image circle? No, it magnifies the central portion of the image to fill the original image circle...at the cost of a stop of light. All that says is that you can make a 400/4 or a 560/5.6 that are about the same diameter and weight. You can't make either of them 'for a crop sensor' and have them be any smaller.

Regardless, having a battle of wits with an unarmed opponent is pointless. I'm out.

Xpenelas · Apr 6, 2026

neuroanatomist said:
Test what? Just because a smaller sensor crops away the outer portion of the image circle doesn't mean a telephoto lens could be made smaller if designed for a crop sensor. That's the limitation, and that's why no manufacturer makes a long telephoto lens 'for crop sensors'.

No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

neuroanatomist · Apr 6, 2026

Xpenelas said:
Just get a lens and test.
You can put an inferior diameter filter without vignetting or open more the diafragm without softening the corners of the image , cause you don't see the part of the image it's losening sharpness .

Test what? Just because a smaller sensor crops away the outer portion of the image circle doesn't mean a telephoto lens could be made smaller if designed for a crop sensor. That's the limitation, and that's why no manufacturer makes a long telephoto lens 'for crop sensors'.

the unused diameter, almost 1/3 at 400mm

Do you really believe that a 400mm f/4 lens 'made for an APS-C sensor' could have a 66mm front element? LOL. No...just, no.

Xpenelas · Apr 6, 2026

neuroanatomist said:
Sorry, but no. You can argue with physics, but you will lose. Every. Single. Time.

There is no 'unused diameter' to remove. With telephoto lens designs, the limiting factor is the entrance pupil diameter and that is coincident with the front element. A 400mm f/4 lens will need a 100mm front element (slightly less, because really a lens called a 400/4 would be something like a 392mm f/4.13 and thus could have a 95mm front element). A smaller sensor won't change that.

DO will make the lens shorter, not lighter or smaller in diameter.

Try an empirical comparison. The OM 150-400mm f/4.5 is 115mm in diameter and weighs 1.9 kg. The Canon EF 400mm f/4 DO is 128mm in diameter and weighs 2.1 kg. The OM lens is for m4/3 sensors with a 2x crop factor, yet it's pretty much the same diameter and weight as the FF lens from Canon (the differences are because the OM lens is 1/3-stop slower).

Just get a lens and test.
You can put an inferior diameter filter without vignetting or open more the diafragm without softening the corners of the image , cause you don't see the part of the image it's losening sharpness .

neuroanatomist · Apr 6, 2026

Bob Howland said:
Are you serious? You're correct about the ISO and I modified my previous posing but I replied to your cited posting, three posts later. Can't you read?

Yes, but I said properly understand. Clearly, you don't. Just because you prefer 'keeping the same FOV and exposure and letting the DOF fall where it may' doesn't mean that's a universal belief.

Bob Howland said:
It's not f/6.3. It's a 15-70 f/4 lens with the DOF of a 15-70 f/4 lens, regardless of the size of sensor. The only reason the DOF changes is when people move forward or back or change the focal length to maintain the same FOV.

You should have stopped with the above. That was a correct statement.

neuroanatomist · Apr 6, 2026

Xpenelas said:
No we want cause market is not enought, but, not cause the lenses couldn't be less size and weight. The smaller the image circle the nearer the back lens could be an with DO you could remove all the unused diameter, almost 1/3 at 400mm, of the front lenses or get faster aperture.

Sorry, but no. You can argue with physics, but you will lose. Every. Single. Time.

There is no 'unused diameter' to remove. With telephoto lens designs, the limiting factor is the entrance pupil diameter and that is coincident with the front element. A 400mm f/4 lens will need a 100mm front element (slightly less, because really a lens called a 400/4 would be something like a 392mm f/4.13 and thus could have a 95mm front element). A smaller sensor won't change that.

DO will make the lens shorter, not lighter or smaller in diameter.

Try an empirical comparison. The OM 150-400mm f/4.5 is 115mm in diameter and weighs 1.9 kg. The Canon EF 400mm f/4 DO is 128mm in diameter and weighs 2.1 kg. The OM lens is for m4/3 sensors with a 2x crop factor, yet it's pretty much the same diameter and weight as the FF lens from Canon (the differences are because the OM lens is 1/3-stop slower).

mangobutter · Apr 6, 2026

id rather the 40 2.8 be resurrected for RF. i'm in love with its optical qualities. if canon can play with the EF 50 STM and repurpose it for RF mount, i dont see why canon can't do the same for the EF 40 2.8.

mangobutter · Apr 6, 2026

I love my beast of a lens, the 100-400L II. The all metal feel, aesthetic, and construction is top notch and the IQ is stellar. I double purpose this lens and use it with my Fujifilm bodies and works essentially like native on it. I replaced the collar with one from RRS.

Bob Howland · Apr 6, 2026

neuroanatomist said:
Must? No, you can change the ISO. Like all triangles, the exposure triangle has three sides.

It's been a few months since I posted a couple of good links that explain equivalence. I'm guessing you didn't read them, but I'll post them again in case someone other than you actually wants to try to properly understand the concept.

This link has a thorough explanation of the concept:

Equivalence

This link is a decent summary:

What is equivalence and why should I care?

Equivalence, at its most simple, is a way of comparing different formats (sensor sizes) on a common basis. Sounds straightforward enough, but the concept is still somewhat controversial and not always clearly understood. We thought it was about time we explained - and demonstrated - what...

www.dpreview.com

Are you serious? You're correct about the ISO and I modified my previous posing but I replied to your cited posting, three posts later. Can't you read?

Xpenelas · Apr 6, 2026

neuroanatomist said:
No, we won't. Not ever. Because physics. A 400/4 or 500/4 would be the same size and weight for an APS-C image circle as for a FF image circle.

No we want cause market is not enought, but, not cause the lenses couldn't be less size and weight. The smaller the image circle the nearer the back lens could be an with DO you could remove all the unused diameter, almost 1/3 at 400mm, of the front lenses or get faster aperture.

neuroanatomist · Apr 6, 2026

Bob Howland said:
To maintain the same DOF for same FOV with differently sized sensors and the same subject distance, the 15-70 and 24-112 lenses must have different apertures, which means they must have different shutter speeds, which may or may not be important, depending the situation and the photographer's intent. I prefer keeping the same FOV and exposure and letting the DOF fall where it may.

Must? No, you can change the ISO. Like all triangles, the exposure triangle has three sides.

It's been a few months since I posted a couple of good links that explain equivalence. I'm guessing you didn't read them, but I'll post them again in case someone other than you actually wants to try to properly understand the concept.

This link has a thorough explanation of the concept:

Equivalence

This link is a decent summary:

What is equivalence and why should I care?

Equivalence, at its most simple, is a way of comparing different formats (sensor sizes) on a common basis. Sounds straightforward enough, but the concept is still somewhat controversial and not always clearly understood. We thought it was about time we explained - and demonstrated - what...

www.dpreview.com

Xpenelas · Apr 6, 2026

zapper said:
He said "f/6.3 equivalent", which is (approximately) correct. It will take similar photos to a hypothetical 24-112mm f/6.4 full frame (same position, same DOF, same FOV, same shutter speed, same image quality with the full frame aperture and ISO 1.6x higher than APS-C). However, the hypothetical 24-112mm f/6.4 will take photos with higher IQ if the exposure permits base ISO, compared to the 15-70 f/4.

I would not buy a f/6.4 FF mid zoom, nor I would not buy a f/4 APS-C mid zoom. I consider FF f/4 to be acceptable compromise of versatility, IQ, and size/weight for wide and mid zooms, and f/2.8 to be acceptable on APS-C (I have the Sigma 10-18 and 18-50 f/2.8 lenses). I would LOVE a 15-70 f/2.8 RF-S lens. But f/4 on APS-C is a stop slower than I want.

None of that equivalencies are true.

APS-C F4 needs just the same exposure for the same image. Just the DOF change affirmation are something near reality, and just cause you are nearer to the subject on FF, not even 1/2 stop equivalent nearer, but you need M43 just that stop DOF lose, not APS-C.

danfaz · Apr 6, 2026

Click said:
I really like your pictures. Lovely reflections in the first two.

Thank you, Click!

Bob Howland · Apr 6, 2026

zapper said:
He said "f/6.3 equivalent", which is (approximately) correct. It will take similar photos to a hypothetical 24-112mm f/6.4 full frame (same position, same DOF, same FOV, same shutter speed, same image quality with the full frame aperture and ISO 1.6x higher than APS-C). However, the hypothetical 24-112mm f/6.4 will take photos with higher IQ if the exposure permits base ISO, compared to the 15-70 f/4.

I would not buy a f/6.4 FF mid zoom, nor I would not buy a f/4 APS-C mid zoom. I consider FF f/4 to be acceptable compromise of versatility, IQ, and size/weight for wide and mid zooms, and f/2.8 to be acceptable on APS-C (I have the Sigma 10-18 and 18-50 f/2.8 lenses). I would LOVE a 15-70 f/2.8 RF-S lens. But f/4 on APS-C is a stop slower than I want.

To maintain the same DOF for same FOV with differently sized sensors and the same subject distance (update: and the same ISO), the 15-70 and 24-112 lenses must have different apertures, which means they must have different shutter speeds, which may or may not be important, depending the situation and the photographer's intent. I prefer keeping the same FOV and exposure and letting the DOF fall where it may.

Latest activity

Latest activity

Filter

Forum statistics

Gallery statistics